DEPT OF ECE EC T71 ENGINEERING ECONOMICS
RAJESWARI S-AP/ECE Page No:1
UNIT – I
PART - A
1. What is meant by economics?
Economics is the science that deals with the production and consumption of goods and
services and the distribution and rendering of these for human welfare.
2. Define engineering economics.
The application of economic principles to engineering problems, for example in
comparing the comparative costs of two alternative capital projects or in determining the
optimum engineering course from the cost aspect.
3. What is managerial economics?
Managerial Economics is the application of economic theory and methodology
to managerial decision making problems within various organizational settings such as a
firm or a government agency.
4. Explain the objectives of managerial economic
1. Growth the business
2. Maximize the profit
3. Maintain the demand and supply
5. Difference between Microeconomics and Macroeconomics.
Microeconomics is the study of particular markets, and segments of the economy. It looks
at issues such as consumer behaviour, individual labour markets, and the theory of firms.
Macroeconomics is the study of the whole economy. It looks at ‘aggregate’ variables, such
as aggregate demand, national output and inflation.
6. Define Managerial Decision.
Any decision regarding the operation of a firm, These decisions include setting target
growth rates, hiring or firing employees, and deciding what products to sell.
7. Explain the profit maximization theory of the firm.
Marginal revenue displays the added revenue from each product sold, the reason the line
has a negative gradient is the factor that as there is a greater quantity supplied.
8. Define Marries balanced rate of growth theory of the firm.
The firm is assumed to grow by diversification and not by merger or acquisition.
The growth of demand for the products of the firm depends on the rate of diversification
and the proportion of successful new products.
9. What is the basic postulate of the behavioral model of cyert and March?
Behavioural Theory of the Firm developed comprehensively by R.M.Cyert and J.G.March
The model has the following sequence:
The firm as a coalition of groups with conflicting goals and interests.
The process of formation of goals of the various groups within the firm.
Defining goals of the firm by top management: satisfying behaviour of the firm.
10. What is decision making? Discuss its important
Decision-making can be regarded as the cognitive process resulting in the selection of a
belief or a course of action among several alternative possibilities.
12. Define demand.
Demand is the utility for a good or service of an economic agent, relative to a budget
constraint.
13. Define supply.
In economics, supply refers to the amount of a product that producers and firms
are willing to sell at a given price all other factors being held constant.
14. Define cost.
An amount that has to be paid or given up in order to get something.
DEPT OF ECE EC T71 ENGINEERING ECONOMICS
RAJESWARI S-AP/ECE Page No:2
15. Define the factors influencing demand.
Income of the people
Prices of related goods
Tastes of consumers
UNIT - II
PART – A
1. List the criteria for make.
Criteria for make The following are the criteria for make:
1. The finished product can be made cheaper by the firm than by outside suppliers.
2. The finished product is being manufactured only by a limited number of outside firms
which are unable to meet the demand.
2. List the criteria for buy.
Criteria for buy The following are the criteria for buy:
1. Requires high investments on facilities which are already available at supplier’s plant.
2. The company does not have facilities to make it and there are more profitable
opportunities for investing company’s capital.
3. Define the approaches for make or buy decision.
Types of analysis followed in make or buy decision are as follows:
1. Simple cost analysis
2. Economic analysis
3. Break-even analysis
4. List the types of analysis followed in make or buy decision.
Types of analysis followed in make or buy decision are as follows:
1. Simple cost analysis
2. Economic analysis
3. Break-even analysis
5. Define purchase model
Purchase model is used to calculate the purchasing requirement. The formulae to calculate
is given as
02
2
(1 )C
C DQ
rC
k
6. Define manufacturing mode
Manufacturing model is used to calculate the purchasing requirement. The formulae to
calculate is given as
02
2
(1 )C
C DQ
rC
k
7. Explain value analysis.
Value Analysis is the systematic application of recognized techniques which identify the
function of a product or service, establish a monetary value for the function and provide
the necessary function reliably at the lowest overall cost.
8. State value engineering.
Value engineering is the application of exactly the same set of techniques to a new product
at the design stage, project concept or preliminary design when no hardware exists to
ensure that bad features are not added.
DEPT OF ECE EC T71 ENGINEERING ECONOMICS
RAJESWARI S-AP/ECE Page No:3
9. Define value.
The term ‘value’ is used in different ways and, consequently, has different meanings. The
designer equates the value with reliability; a purchase person with price paid for the item;
a production person with what it costs to manufacture and a sales person with what the
customer is willing to pay. Value, in value investigation, refers to “economic value”,
10. List the four types of economic value.
1. Cost value
2. Exchange value,
3. Use value
4. Esteem value
11. Define performance
The performance of a product is the measure of functional features and properties that
make it suitable for a specific purpose.
12. Define function.
Function is the purpose for which the product is made.
13. List the classification of function.
1. Primary function
2. Secondary function
3. Tertiary function
14. Write a short note on primary and secondary function.
Primary functions: are the basic functions for which the product is specially designed to
achieve. Primary functions, therefore, are the most essential functions whose non-
performance would make the product worthless, e.g. a photo frame exhibits photographs,
a chair supports weight, a fluorescent tube gives light.
Secondary functions: are those which, if not in-built, would not prevent the device from
performing its primary functions, e.g., arms of a chair provided support for hands.
Secondary functions are usually related to convenience. The product can still work and
fulfill its intended objective even if these functions are not in-built and yet they may be
necessary to sell the product.
15. Define aim in economics.
To attempt or intend to reach a certain goal.
UNIT - III
PART - A
1. Define present worth method.
In this method of comparison, the cash flows of each alternative will be reduced to time
zero by assuming an interest rate i. Then, depending on the type of decision, the best
alternative will be selected by comparing the present worth amounts of the alternatives.
2. Draw the revenue dominated cash flow diagram.
3. Write the formula to find the present worth method.
PW(i) = – P + R1[1/(1 + i)1] + R2[1/(1 + i)
2] + ...
+ Rj[1/(1 + i) j] + Rn[1/(1 + i)
n] + S[1/(1 + i)
n]
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RAJESWARI S-AP/ECE Page No:4
4. Draw the cash -dominated cash flow diagram.
5. Write the formula to compute the cash dominated present worth.
PW(i) = P + C1[1/(1 + i)1] + C2[1/(1 + i)
2] + ... + Cj[1/(1 + i)
j]
+ Cn[1/(1 + i)n] – S[1/(1 + i)
n]
6. Write the two techniques to find future worth method.
1. Revenue dominated
2. Cash dominated
7. Draw the revenue dominated cash flow diagram for future method.
8. Write the formula to find the present worth method.
FW(i) = –P(1 + i)n+ R1(1 + i)
n–1+ R2(1 + i)
n–2+ ...
+ Rj(1 + i)n–j
+ ... + Rn + S
9. What is annual equivalent method of comparing alternatives?
In this method, the mutually exclusive alternatives are compared on the basis of
equivalent uniform annual worth. The equivalent uniform annual worth represents the
annual equivalent value of all the cash inflows and cash outflows of the alternatives at the
given rate of interest per interest period. In this method of comparison, the equivalent
uniform annual worth of all expenditures and incomes of the alternatives are determined
using different compound interest factors namely capital recovery factor, sinking fund
factor and annual worth factors for arithmetic and geometric gradient series etc.
10. Write the formula to compute the cash dominated future worth.
FW(i) = P(1 + i)n+ C1(1 + i )
n–1+ C2(1 + i)
n–2+ ...
+ Cj(1 + i)n–j
+ ... + Cn – S
11. Write down the techniques for comparing the worthiness of the project.
1. Present worth method
2. Future worth method
3. Annual equivalent method
12. Define Annual equivalent method
A generalized revenue-dominated cash flow diagram to demonstrate the annual equivalent
method of comparison is
13. Define Annual equivalent method.
A generalized cost-dominated cash flow diagram to demonstrate the annual equivalent
method of comparison is
13. Define rate of return method.
DEPT OF ECE EC T71 ENGINEERING ECONOMICS
RAJESWARI S-AP/ECE Page No:5
The rate of return of a cash flow pattern is the interest rate at which the present worth of
that cash flow pattern reduces to zero. In this method of comparison, the rate of return for
each alternative is computed.
15. What is cash dominated cash flow diagram?
A cash flow diagram is a tool used by accountants and engineers, to represent the
transactions of cash which will take place over the course of a given project. Transactions
can include initial investments, maintenance costs, projected earnings or savings resulting
from the project, as well as salvage and resale value of equipment at the end of the
project.
UNIT - IV
PART - A
1. Write the different types of maintenance.
1. Corrective
2. scheduled
3. predictive
4. preventive
2. Define prevention maintenance (PM).
Preventive maintenance (PM) is the periodical inspection and service activities which are
aimed to detect potential failures and perform minor adjustments or repairs which will
prevent major operating problems in future.
3. Define Break down maintenance.
Breakdown maintenance is the repair which is generally done after the equipment has
attained down state. It is often of an emergency nature which will have associated penalty
in terms of expediting cost of maintenance and down time cost of equipment.
4. Write the different types of Replacement.
Replacement study can be classified into two categories:
1. Replacement of assets that deteriorate with time (Replacement due to gradual failure,
or wear and tear of the components of the machines).
2. Simple probabilistic model for assets which fail completely (replacement due to
sudden failure).
5. Define economic life of an asset.
Any asset will have the following cost components:
1. Capital recovery cost (average first cost), computed from the first cost (purchase price)
of the machine.
2. Average operating and maintenance cost (O & M cost)
3. Total cost which is the sum of capital recovery cost (average first cost) and average
maintenance cost.
6. What are the types of Replacement policies?
1. A thorough replacement analysis.
2. An understanding of replacement drivers.
3. Evaluation of replacement cost.
7. What is meant by economic life of an asset?
A simple model to calculate Economic Life shows how the impact of Continuous
Improvement on asset life can be readily assessed.
8. Name the types of maintenance.
1. Preventive maintenance
2. Break down maintenance
9. List down the types of replacement problem.
1. Replacement of assets that deteriorate with time.
2. Simple probabilistic model for assets which fails completely
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RAJESWARI S-AP/ECE Page No:6
10. What is replacement analysis?
Replacement analysis involves the replacement of existing obsolete or worn out accepts
in order to avoid failure in operations
11. State the main causes of breakdown
1. Lack of lubrication
2. In-difference towards minor fault
12. State any two disadvantages of breakdown maintenance.
1. Delays in production
2. Faster deterioration
13. Define economic life.
The point where the total cost is minimum is called the economic life of the machine.
14. What is meant by challenger?
If existing equipment is considered for replacement with new equipment, then the
existing equipment is known as the defender and the new equipment is known as
challenger.
15. What is meant by defender?
If existing equipment is considered for replacement with new equipment, then the
existing equipment is known as the defender
UNIT V
PART –A
1. Define Depreciation.
The recovery of money from the earnings of equipment for its replacement purpose is
called depreciation fund since we make an assumption that the value of the equipment
decreases with the passage of time. Thus, the word “depreciation” means decrease in value
of any physical asset with the passage of time.
2. What are the types of Depreciation?
1. Straight line method of depreciation
2. Declining balance method of depreciation
3. Sum of the years—digits method of depreciation
4. Sinking-fund method of depreciation
5. Service output method of depreciation
3. Define Straight line method of depreciation.
In this method of depreciation, a fixed sum is charged as the depreciation amount
throughout the lifetime of an asset such that the accumulated sum at the end of the life of
the asset is exactly equal to the purchase value of the asset. Here, we make an important
assumption that inflation is absent.
4. Define Declining balance method of depreciation.
In this method of depreciation, a constant percentage of the book value of the previous
period of the asset will be charged as the depreciation amount for the current period. This
approach is a more realistic approach, since the depreciation charge decreases with the life
of the asset which matches with the earning potential of the asset.
5. Define Sum of the year-digits method of depreciation.
In this method of depreciation also, it is assumed that the book value of the asset decreases
at a decreasing rate. If the asset has a life of eight years, first the sum of the years is
computed as Sum of the years = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 = 36 = n(n + 1)/2
6. Define sinking fund method of depreciation.
In this method of depreciation, the book value decreases at increasing rates with respect to
the life of the asset.
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RAJESWARI S-AP/ECE Page No:7
7. Define Service output method of depreciation.
In some situations, it may not be realistic to compute depreciation based on time period. In
such cases, the depreciation is computed based on service rendered by an asset.
8. Define inflation
In economics, inflation is a sustained increase in the general price level of goods and
services in an economy over a period of time. It can be defined as too much money chasing
too few goods. When the general price level rises, each unit of currency buys fewer goods
and services.
9. What is depreciation fund?
The recovery of money from the earnings of equipment for its replacement purpose is called
depreciation fund
10. Give the expression for the calculation of depreciation under sum of years-digit
method of depreciation.
SYD Depreciation=Remaining useful life/Sum of the years
11. What is evaluation of public alternative?
Evaluation of public alternative is nothing but the selecting of best alternative from the
available alternatives.
12. List the few causes of depreciation.
The causes of depreciation are:
1. Wear and tear
2. Depletion
3. Obsolescence
4. Lapse of time
13. What are the assumptions for straight line method of calculation depreciation?
Inflation is absent
14. List the methods of depreciation.
1. Straight line method of depreciation
2. Declining balance method of depreciation
3. Sum of the years—digits method of depreciation
4. Sinking-fund method of depreciation
5. Service output method of depreciation
15. Write the formula to find the declining balance method of depreciation.
DT = Rate′(P − F)
DEPT OF ECE EC T72 MICROWAVE & OPTICAL ENGINEERING
K.SHIYAMALA-AP/ECE Page No:8
UNIT- I
PART-A
1. Define Gunn Effect.
Gunn Effect was first observed by Gunn in type GaAs bulk diode. According to Gunn, above
some critical voltage corresponding to an electric field of 2000-4000v/cm, the current in
every specimen became a fluctuating function of time. The frequency of oscillation was
determined mainly by the specimen and not by the external circuit.
2. What is the necessary condition for an IMPATT to produce oscillations?
An IMPATT diode (Impact ionization Avalanche Transit-Time) is a form of high-
power diode used in high-frequency electronics and microwave devices.
The IMPATT diode family includes many different junctions and metal semiconductor
devices.
3. List the differences between microwave transistor and TED devices.
Step recovery diodes, transistors, tunnel diodes,& TEDs are active microwave devices that
generate power or amplify microwave signals.
4. What are the advantages of parametric amplifier?
Microwave and audio parametric amplifiers were used as low-noise amplifiers, to process
low-level signals. Therefore their non-linearity probably never occurred in use
5. What is meant by avalanche transit time device?
Negative resistance is achieved by creating a delay (1800 Phase shift) between the voltage
and current. Delay is achieved by, Delay in generating the avalanche current multiplication
& Delay due to transit time through the material So called Avalanche transit time (ATT)
devices
6. Mention the applications of PIN diode.
RF switches,
Attenuators,
Photo detectors,
Phase shifters
7. What is a parametric amplifier?
Parametric amplification is a phenomenon where a signal can be amplified using a
parametric nonlinearity and a pump wave. This focuses on optical amplification, even
though there are also electronic parametric amplifiers, used e.g. for microwaves. 8. What is the theory of a negative resistance amplifier?
A device exhibiting negative resistance can be used to amplify a signal and this is an
especially useful technique at microwave frequencies. Such devices do not present as
pure negative resistance at these frequencies (in the case of the tunnel diode a large
parallel capacitance is also present) and a matching filter is usually required.
The reactive components of the device's equivalent circuit can be absorbed into the filter
design so the circuit can be represented as a pure resistance followed by a bandpass
filter.
The output of this arrangement is fed into one port of a three-port circulator. The other
two ports constitute the input and output of the amplifier with the direction of
circulation.
9. Explain how a tunnel diode can be used as a amplifier.
A circuit showing how a tunnel diode can amplify a signal using negative differential
resistance. The DC voltage Vb biases the tunnel diode TD into its negative resistance region
and also supplies the power used in amplifying the signal. For stability the resistor R must be
less than the diodes negative resistance r. Therefore the total resistance of both devices in
series, r - R is a small negative value.
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10. Mention the main application of IMPATT diode.
Used as transmitter for microwave communication systems.
11. State the performance characteristics of IMPATT and TRAPATT diode.
IMPATT
Efficiency=30%
Frequency=1 to 300 GHz
Pulsed Power= 4 KW
TRAPATT
Efficiency=15 to 50%
Frequency=3 to 50 GHz
Power= 1 to 3 KW.
12. Write the applications of Tunnel Diode.
Used in self excited mixers.
High speed switching and logic operations.
Low power oscillators.
13. What are the applications of reflex klystron?
Signal source in microwave generators.
Local oscillators in receivers.
Pump oscillators in parametric amplifiers
14. What is the purpose of slow wave structures used in TWT amplifiers?
Operation is similar to that of a klystron, except that coupled-cavity TWTs are designed
with attenuation between the slow-wave structure instead of a drift tube. The slow-wave
structure gives the TWT its wide bandwidth. A free electron laser allows higher
frequencies. 15. State the applications of TWT.
TWT are an ideal form of RF amplifier, commonly used in satellite transponders where
low levels signals are received and need to be retransmitted at much higher levels.
In addition to this TWT amplifiers are used in microwave radar systems where they are
able to produce the high levels of power required.
Traveling wave tube, TWT technology is also used for electronic warfare applications.
In these applications the grid on the traveling wave tube may be used to pulse the
transmission.
UNIT-II
PART-A
1. State Faraday’s rotation law.
If a circularly polarized wave is made to pass through a ferrite rod which has been influenced
by an axial magnetic field B, then the axis of polarization gets tilted in clockwise direction
and amount of tilt depends upon the strength of magnetic field and geometry of the
ferrite.
2. State the properties of S matrix.
It possess symmetric property sij =sji
It possess unitary property [s][s]*=[i]
3. What are the reasons that low frequency parameters cannot be measured in
microwaves?
Bandwidth, improved directivity with an aerial array, reliability, power requirement
4. State the two parameters that describe a directional coupler? Define them.
The important parameters of a directional coupler are: Coupling factor and Coefficient.
A directional coupler is a useful hybrid wave guide joint which couples power in a
auxiliary wave guide arm in one direction.
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5. What is Tee junction? Give two examples
In Microwave circuits a wave guide or coaxial junction with three independent ports is
referred to as Tee junction. Eg: E- Plane Tee, H-plane Tee
6. What is S matrix and write the S matrix of N port network?
S11 S12 S13 … S1n
[ S ] = S21 S22 S23 .. S2n
S31 S32 S33 .. S3n
Sm1 Sm2 Sm3 .. Smm
7. What is meant by hybrid coupler? A hybrid coupler is a passive device used in radio and telecommunications. It is a type of
directional coupler where the input power is equally divided between two output ports. Since
it is a special case of directional coupler, it is discussed in Power dividers and directional
couplers.
8. Compare z parameters and ABCD parameters with S-parameters.
A= Z11/Z12, B=-(Z11 Z22-Z12 Z21)/Z21
C= 1/Z21,B=-Z22/Z21
9. What are hybrid rings?
Hybrid ring consists of an annular line of proper electrical length to sustainstanding waves,
to which four arms are connected at proper intervals by means of series or parallel
junctions.
10. List the parameters that determine the performance of a directional coupler.
Coupling coefficient
Directivity
Insertion loss
Isolation.
11. What are the advantages of ABCD matrix?
They are used in power transmission lines.
They are very helpful in the case of cascade networks.
12. Define one port network.
A one port circuit is a circuit for which power can enter or leave through a single
waveguide or transmission lines.
13. Define s-matrix.
At microwave frequencies the measurable quantities are power, reflection coefficient,
transmission coefficient and standing wave ratio. A linear relation between input and
output of a microwave network in terms of precisely measurable parameters is called
scattering description (or scattering matrix is a matrix made up of scattering coefficients).
14. What is ABCD matrix?
ABCD matrix is a transmission matrix. These parameters express voltage and current at
output in terms of those at input port.
V1=AV2-BI2
I1=CV2-DI2 15. Give an example for a two port Microwave device.
Small signal models for transistors (such as the hybrid-pi model), filters
Matching networks.
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UNIT-III
PART-A
1. What is Bolometer?
It is a power sensor whose resistance change with changed temperature as it absorbs
the microwave power. It is a short thin metallic wire sensor with positive temperature
coefficient of resistance.
2. What is transit time?
It is the time taken by the electro to travel from cathode to the plate of an electrode.
3. State the applications of magnetron.
Pulse work in Radar.
Linear particle accelerators.
4. What are the methods to detect microwave power?
Balometer method
Calorimeter method
5. What is meant by duty cycle?
When you change the power setting on most microwaves, it doesn't change the power output
of the magnetron. It changes the duty cycle, i.e. when the magnetron is on and when it is off.
6. How are microwave measurements different from low frequency measurements?
The low-frequency measurements are direct capacitance measurements performed with an
LCR meter and the capacitance determination at microwave frequencies is done by
extracting the capacitance from S-parameter measurement results. Several discrete and
monolithically integrated Schottky diodes are measured with both techniques and the
differences of the techniques are discussed in the view of the obtained results.
7. State the four types of TWT.
Broadband, Low noise, Low level amplifiers.
CW power TWT
Pulsed TWT
Dual mode TWT
8. How the Klystron amplifier can act as Klystron oscillator?
When the klystron amplifier is given a positive feedback such that the overall phase shift
becomes 0 or 360. Then the klystron amplifier acts as an oscillator.
9. Why magnetron is called as cross field device?
In cavity magnetron, there exist radial electric field and an axial magnetic field
perpendicular to each other and hence magnetron is called as a cross field device.
10. List any two methods of measuring impedance of a terminating load in a microwave
system.
Slotted line
Reflectometer
11. Give the main classifications of magnetron.
Negative resistance
Cyclotron frequency
Travelling wave.
12. What is a VSWR meter?
VSWR meter is a highly sensitive, high gain, high theta, low noise voltage amplifier tuned
normally at fixed frequency of 1KHZ of which microwave signals modulated. This meter
indicates calibrated VSWR reading fir any loads.
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13. Define insertion loss.
It is defined as difference in power arriving at the terminating load with or without The
network in circuit.
14. How do you measure microwave frequency?
Wave meter method
Slotted line method
Down conversion method
15. List the methods for measuring dielectric constants.
Waveguide method
cavity perturbation method
UNIT IV
PART-A
1. Define optical communication.
Optical communication, also known as optical telecommunication, is communication at a
distance using light to carry information. It can be performed visually or by using electronic
devices.
2. What is meant by propagation of light?
A light ray is a line or curve that is perpendicular to the light's wave fronts (and is therefore
collinear with the wave vector). Light rays bend at the interface between two dissimilar
media and may be curved in a medium in which the refractive index changes. Geometric
optics describes how rays propagate through an optical system. Objects to be imaged are
treated as collections of independent point sources, each producing spherical wave fronts
and corresponding outward rays.
3. Define numerical aperture.
Numerical aperture (N.A) of the fiber is the light collecting efficiency of the fiber and is the
measure of the amount of light rays that can be accepted by the fiber. It is equal to the sine
of acceptance.
4. What are the various losses in optical fiber?
In an optical fiber cable(OFC) mainly there are following types of losses :- 1) Bending loss
(Due to Macro bends & Micro bends) 2) Scattering loss (Rayleigh scattering & Mie
scattering) 3) Dispersion loss 4) Absorption loss 5) Insertion loss
5. What is meant by scattering loss?
Attenuation is the main loss mechanism in an optical fiber. Absorption and scattering of
signals results in attenuation. There are two types of scattering losses. They are linear
scattering and nonlinear scattering. In linear scattering, attenuation occurs when optical
power is transferred from one mode to another keeping frequency unaltered. Non linear
scattering occurs when frequency is changed during optical power transfer.
6. What is meant by radiation loss?
Radiation losses are caused mainly by small bends and kinks (twist) in the fiber.
Essentially, there are two types of bends: micro bends and macro bends. Micro bending
occurs as a result of differences in the thermal contraction rates between the core and the
cladding material. A micro bend is a miniature bend or geometric imperfection along the
axis of the fiber and represents a discontinuity in the fiber where Rayleigh scattering can
occur. Macro bends are caused by excessive pressure and tension and generally occur when
fibers are bent during handling or installation.
7. What is meant by dispersion loss?
Dispersion is the broadening of light pulses as it propagates through the fiber. It increases
with length of the fiber. Excessive dispersion causes over-lapping of adjacent pulses or inter
symbol interference. So dispersion has a negative effect on the bandwidth of a fiber. The
higher the dispersion, lie lower will he bandwidth of the system. Dispersion also decreases
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the peak optical power of the pulse and therefore increases the effective attenuation of a
fiber,
8. What is Snell’s law?
The relationship at the interface is known as Snell’s law and is given by
n1sinφ1= n2sinφ2
9. What are the advantages of LED?
LEDs are less complex circuits than Laser diodes.
Fabrication is easier.
They have long life.
10. What are the two types of LED configuration?
Homo junction
Single and double hetero junction.
11. What are the advantages of Photodiodes?
Small size
Suitable material
High sensitivity
Fast response time
12. What are the types of photodiode?
• PIN photo detector
• Avalanche photodiode (APD)
13. Define avalanche effect.
The newly created carriers are accelerated by the high electric field, thus gaining enough
energy to cause further impact ionization. This phenomenon is called avalanche effect.
14. What is meant by total internal reflection?
The ray should travel from denser to rarer i.e. from core to clad region of the fiber and the
angle of incidence in the denser medium should be greater than the critical angle of that
medium.
15. Define modal dispersion.
Modal dispersion is a distortion mechanism occurring in multimode fibers and other
waveguides, in which the signal is spread in time because the propagation velocity of the
optical signal is not the same for all modes.
UNIT V
PART-A
1. Draw the block diagram of fiber optic system.
2. Define point to point link.
In telecommunications, a point-to-point connection refers to a communications connection
between two nodes or endpoints.
3. What is the method of fiber splicing?
There are 3 methods of fiber splicing. They are:
• Electric arc fusion splicing or fusion splicing
• Mechanical splicing
• V-groove splicing or loose tube splicing
4. What is meant by acceptance angle?
DEPT OF ECE EC T72 MICROWAVE & OPTICAL ENGINEERING
K.SHIYAMALA-AP/ECE Page No:14
The maximum angle ‘Φmax’ with which a ray of light can enter through the entrance end
of the fiber and still be totally internally reflected is called acceptance angle of the fiber.
5. What are step index and graded index fibers?
In the case of graded index fiber, the refractive index of a core is a constant and is larger
than the refractive index of the cladding. The light propagation is mainly by meridional
rays. In the case of graded index fiber (GRIN fiber) the refractive index of the core varies
parabolically from the centre of the core having maximum refractive index to the core-
cladding interface having constant minimum refractive index. Here the light propagation is
by skew rays.
6. Why do we prefer step index fiber for long distance communication?
Step index single mode fiber has a)low attenuation due to smaller core diameter b) higher
bandwidth and c) very low dispersion.
7. Define WDM.
In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology
which multiplexes a number of optical carrier signals onto a single optical fiber by using
different wavelengths (i.e., colors) of laser light. This technique enables bidirectional
communications over one strand of fiber, as well as multiplication of capacity.
8. What is meant by SONET?
Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) are
standardized protocols that transfer multiple digital bit streams synchronously over optical
fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At low
transmission rates data can also be transferred via an electrical interface.
9. Define AON.
An active optical system uses electrically powered switching equipment, such as a router or
a switch aggregator, to manage signal distribution and direct signals to specific customers.
This switch opens and closes in various ways to direct the incoming and outgoing signals to
the proper place. In such a system, a customer may have a dedicated fiber running to his or
her house.
10. Define PON.
A passive optical network, on the other hand, does not include electrically powered
switching equipment and instead uses optical splitters to separate and collect optical signals
as they move through the network. A passive optical network shares fiber optic strands for
portions of the network. Powered equipment is required only at the source and receiving
ends of the signal.
11. What is meant by Rayleigh scattering?
The index variation causes a Rayleigh type of scattering of light. Rayleigh scattering in
glass in the same phenomenon that scatters light from sun in the atmosphere, giving rise to
blue sky.
12. What is the measure of information capacity in optical waveguide?
It is usually specified by bandwidth distance product in MHz. For a step index fiber the
various distortion effects tend to limit the bandwidth distance product to 20MHz.
13. Mention the losses responsible for attenuation in optical fibers.
Absorption losses, Scattering losses and bending losses
14. What do you meant by extrinsic absorption?
Absorption phenomena due to impurity atoms present in the fiber.
15. Define microscopic bending.
Fibers losses occur due to small bending arise while the fiber is inserted into a cable.
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UNIT 1
PART-A
1. What is an embedded system?
An embedded system employs a combination of hardware & software (a “computational
engine”) to perform a specific function; is part of a larger system that may not be a
“computer”; works in a reactive and time-constrained environment.
2. What are the components of the Embedded Systems?
An embedded system is basically a computer controlled device designed to perform some
specific tasks. In most cases these tasks revolve around real-time control of machines or
processes. Embedded systems are more cost effective to implement than systems
composed of general purpose computers, such as PCs. The components of ES are,
Memory
System Clock
Peripherals
3. What is the Classification of an embedded system?
The Embedded system is classified into following category
Small Scale Embedded System
Medium Scale Embedded System
Sophisticated Embedded System
4. What is Sophisticated Embedded System?
The sophisticated embedded system has the following features,
Enormous hardware and software Complexity.
This may need scalable processor or configurable processor and programming logic
arrays.
Constrained by the processing speed available in their hardware units.
5. What are the characteristics of an embedded system?
The typical characteristics of the embedded Systems are as follows:
1) Embedded systems are designed to do some specific task, rather than be a general-
purpose computer for multiple tasks. Some also have real-time performance constraints
that must be met, for reason such as safety and usability; others may have low or no
performance requirements, allowing the system hardware to be simplified to reduce costs.
2) Embedded systems are not always separate devices. Most often they are physically
built-in to the devices they control.
3) The software written for embedded systems is often called firmware, and is stored in
read-only memory or Flash memory chips rather than a disk drive. It often runs with
limited computer hardware resources: small or no keyboard, screen, and little memory.
6. What are the advantages of embedded system?
The advantages of the embedded system are Customization yields lower area, power, cost.
7. What are the disadvantages of embedded system?
Higher HW/software development overhead
design, compilers, debuggers, ...
May result in delayed time to market.
8. What are the various embedded system requirements?
Types of requirements imposed by embedded applications:
• R1 Functional requirements
• R2 Temporal requirements
• R3 Dependability requirements
9. What are the functional requirements of embedded system?
The functional requirements of the embedded systems are as follows:
Data Collection
Sensor requirements
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Signal conditioning
Alarm monitoring
Direct Digital Control
Actuators
Man-Machine Interaction
Informs the operator of the current state of the controlled object
Assists the operator in controlling the system.
10. What are the temporal requirements of the embedded systems?
The temporal requirements of the embedded systems:
Tasks may have deadlines
• Minimal latency jitter
• Minimal error detection latency
• Timing requirements due to tight software control loops
• Human interface requirements.
11. What are dependability requirements of an embedded system?
The dependability requirements of an embedded system are as follows
Safety
critical failure modes
certification
Maintainability
MTTR in terms of repairs per hour
Availability
A = MTTF / (MTTF + MTTR)
Security
12. What is a Microprocessor?
A silicon chip that contains a CPU. In the world of personal computers, the terms
microprocessor and CPU are used interchangeably. At the heart of all personal
computers and most workstations sits a microprocessor. Microprocessors also control the
logic of almost all digital devices, from clock radios to fuel-injection systems for
automobiles.
13. What is a Microcontroller?
It is a small and low-cost computer built for the purpose of dealing with specific tasks,
such as displaying information in a microwave LED or receiving information from a
television’s remote control. Microcontrollers are mainly used in products that require a
degree of control to be exerted by the user.
14. What are differences between Microprocessor and Microcontroller?
MICROPROCESSOR MICROCONTROLLERS
The functional blocks are
ALU, registers, timing &
control unit.
It includes functional blocks of
microprocessors & in addition
has timer, parallel i/o, RAM,
EPROM, and ADC & DAC.
Bit handling instruction is less,
one or two type only.
Many types of bit handling
instruction.
Rapid movements of code and
data between external memory
& MP.
Rapid movements of code and
data within me.
It is used for designing general
purpose digital computers
system.
They are used for designing
application specific dedicated
systems.
15. What are the various embedded system designs?
Modeling,Refining (or “partitioning”)
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UNIT –II
PART-A
1. Give the summary of I/O devices used in embedded system
Program, data and stack memories occupy the same memory space. The total addressable
memory size is 64 KB.
Program memory - program can be located anywhere in memory. Jump, branch and call
instructions use 16-bit addresses, i.e. they can be used to jump/branch anywhere within 64
KB. All jump/branch instructions use absolute addressing.
Data memory - the processor always uses 16-bit addresses so that data can be placed
anywhere. Stack memory is limited only by the size of memory. Stack grows downward.
First 64 bytes in a zero memory page should be reserved for vectors used by RST
instructions.
I/O ports
256 Input ports
256 Output ports
Registers
Accumulator or A register is an 8-bit register used for arithmetic, logic, I/O and load/store
operations.
2. Define bus.
Buses: The exchange of information.
Information is transferred between units of the microcomputer by collections of
conductors called buses. There will be one conductor for each bit of information to be
passed, e.g., 16 lines for a 16 bit address bus. There will be address, control, and data
buses
3. What are the classifications of I/O devices?
i. Synchronous serial input and output
ii. Asynchronous serial UART input and output
iii. Parallel one bit input and output
iv. Parallel port input and output
4. Give the steps for accomplishing input output data transfer
Accomplishing input/output data transfer
There are three main methods used to perform/control input/output data transfers.
Software programming (scanning or polling)
• interrupt controlled
• Direct memory access (DMA)
5. Give the limitations of polling technique.
The polling technique, however, has limitations.
• It is wasteful of the processors time, as it needlessly checks the status of all devices all
the time.
• It is inherently slow, as it checks the status of all I/O devices before it comes back to
check any given one again.
• When fast devices are connected to a system, polling may simply not be fast enough to
satisfy the minimum service requirements. Priority of the device is determined
6. What do you meant by bus arbitration?
Bus Arbitration
Most processors use special control lines for bus arbitration, ie, controlling the use of the
address and data bus,
• An input which the DMAC uses to request the bus
• An output(s) indicating the bus status
• An output indicating acceptance of the DMAC\'s bus request
7. What are the two characteristics of synchronous communication?
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• Bytes/frames maintain constant phase difference and should not be sent at random time
intervals. No handshaking signals are provided during the communication.
• Clock pulse is required to transmit a byte or frame serially. Clock rate information is
transmitted by the transmitter.
8. What do you mean by asynchronous communication?
The most basic way of sharing data is by copying the data in question to each server. This
will only work if the data is changed infrequently and always by someone with
administrative access to all the servers in the cluster.
9. What are the characteristics of asynchronous communication?
• Variable bit rate – need not maintain constant phase difference
• Handshaking method is used
• Transmitter need not transmit clock information along with data bit stream.
10. What are the three ways of communication for a device?
i. Separate clock pulse along with data bits
ii. Data bits modulated with clock information
iii. Embedded clock information with data bits before transmitting
11. Expand a) SPI b) SCI
SPI – Serial Peripheral Interface
SCI – Serial Communication Interface
12. What are the features of SPI?
• SPI has programmable clock rates
• Full-duplex mode
• Crystal clock frequency is 8MHz
• Open drain or totempole output from master to slave
13. Define software timer.
A software timer is software that executes the increase/decrease count value on an
interrupt from timer or RTC. Software timer is used as virtual timing device.
14. What are the forms of timer?
• Hardware interrupt timer
• Software timer
• User software controlled hardware timer
• RTOS controlled hardware timer
• UP/DOWN count action timer
• One-shot timer (No reload after overflow and finished states)
16. Define RTC
RTC Stands for Real Time Systems. Once the system starts, do not stop/reset and the
count value cannot be reloaded.
17. What is I2C?
Inter- Integrated Circuit (2-wire/line protocol) which offers synchronous
communication.
Standard speed: 100Kbps and High speed: 400 Kbps
18. What are the bits in I2C corresponding to?
SDA – Serial Data Line and SCL – Serial Clock line
19. What is a CAN bus? Where is it used?
CAN stands for Controller Area Network. Serial line, bi-directional bus used in
automobiles.Operates at the rate of 1Mbps.
UNIT III
PART-A
1. What are the advantages of Assembly language?
It gives the precise control of the processor internal devices and full use of processor
specific features in its instruction sets and addressing modes.
The machine codes are compact, which requires only small memory.
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Device drivers need only few assembly instructions.
2. What are advantages of high level languages?
Data type declaration
Type checking
Control structures
Probability of non-processor specific codes
3. Define In -line assembly
Inserting an assembly code in between is said to be in-line assembly.
4. Mention the elements of C program.
1. Files:
Header files
Source files
Configuration files
Preprocessor directives
2. Functions:
Macro function
Main function
Interrupt service routines or device drivers
3. Others:
Data types
Data structures
Modifiers
Statements
Loops and pointers
5. What is the use of MACRO function?
A macro function executes a named small collection of codes, with the values passed by
the calling function through its arguments.
It has constant saving and retrieving overheads.
6. What is the use of interrupt service routines or device drivers?
It is used for the declaration of functions and datatypes, typedef and executes named set of
codes.
ISR must be small (short), reentrant or must have solution for shared data problem.
7. What are the datatypes available in C language?
Char – 8 bit; byte – 8 bit; short – 16 bit; unsigned short – 16 bit; unsigned int – 32 bit;
int – 32 bit; long double – 64 bit; float – 32 bit; double – 64
8. Mention the data structures available in C language.
1. Queue
2. Stack
3. Array (1-dimentional and multi-dimentional)
4. List
5. Tree
6. Binary-tree
9. Write the syntax for declaration of pointer and Null-pointer.
Syntax for pointer:
void *portAdata
Syntax for Null-pointer:
#define NULL (void*) 0x0000
10. Explain pass by values.
• The values are copied into the arguments of the function.
• Called programs does not change the values of the variables
11. What are the three conditions that must be satisfied by the re-entrant function?
1. All the arguments pass the values and none of the argument is a pointer.
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2. When a non-atomic operation that function should not operate on the function
declared outside.
3. A function does not call a function by itself when it is not reentrant.
12. Explain pass by reference.
• When an argument value to a function is passed through a pointer, then the value can
be changed.
• New value in the calling function will be returned from the called function.
13. Write the syntax for function pointer.
Syntax:
void *<function_name> (function arguments)
14. Define queue.
• A structure with a series of elements.
• Uses FIFO mode.
• It is used when an element is not directly accessed using pointer and index but only
through FIFO.
• Two pointers are used for insertion and deletion.
15. Define stack.
• A structure with a series of elements which uses LIFO mode.
• An element can be pushed only at the top and only one pointer is used for POP.
• Used when an element is not accessible through pointer and index, but only through
LIFO.
UNIT –IV
PART-A
1. What Is An Rtos?
RTOS is an OS for Embedded system for response time and event controlled processes.
2. What Are Rtos Basic Services?
RTOS Services:
•Basic OS functions - PM, RM, MM, DM, FSM, I/o, etc.
•RTOS main functions - RT task scheduling and latency control
•Time management - Time Allocation, time slicing & monitoring for efficiency.
•Predictability - Predicting time behavior and initiation of task
synchronization
•Priorities Management - Allocation and Inheritance
•IPC - Synchronization of Tasks using IPC.
3. Why We Need Rtos?
We need RTOS for the following reasons,
When efficient scheduling in needed for multitasks with time constraints.
Task synchronization is needed.
Interrupt latency Control is needed.
4. What Are The Occasions Where We No Need Rtos?
Small scale embedded system never use RTOS.
Instead of functions in RTOS standard lib functions in C can be used. Example:
malloc(), free(), fopen(), fclose(), etc.
5. What Are Rtos Task Scheduling Models?
Control Flow Strategy
Data Flow Strategy
Control Data Flow Strategy
6. What Are The Features Of Control Flow Strategy?
Complete control of i/p and o/ps.
Co-operative scheduler adopts this strategy.
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Worst case latencies are well defined.
7. What Are The Features Of Data Flow Strategy?
Interrupt occurrences are predictable.
Task control not deterministic. Ex. Network.
Pre-emptive scheduler adopts this strategy.
8. What Are The Features Of Control Data Flow Strategy?
Task scheduler functions are designed with predefined time-out delays.
WC latency is deterministic, because the maximum delay is per-defined.
Cyclic Co-operative Scheduling, Pre-emptive Scheduling, Fixed Time Scheduling,
Dynamic RT Scheduling use this strategy.
9. What Are Basic Functions Of Rtos?
There are various functions that are available in RTOS. They are as follows:
Kernel
Error Handling Functions
Service and system clock Functions
Device drivers, Network Stack send and receive Functions
Time and delay Functions
Initiate and start Functions
Task state switching Functions
ISR Functions
Memory Functions
IPC Functions
10. What Is The Need For Tested Rtos?
While designing a complex embedded system, we need a tested bug free codes for the
following.
•Multiple task functions in C or C++.
•Real time clock based software timers (RTCSWT).
•Software for Co-operative scheduler.
•Software for a Pre-emptive scheduler.
•Device drivers and Device managers.
•Functions for Inter Process Communications.
•Network functions
•Error handling functions and exception handling functions.
•Testing and System debugging software.
A readily available RTOS package provides the above functions and a lot of time is
saved for coding the same.
11. What Are The Options In Rtos?
There are various options for RTOS. They are as follows:
Own RTOS.
Linux Based RTOS.
µC/OS-II.
PSoS, VxWorks, Nucleus, Win CE, Palm OS.
12. What Are Different Phases Of System Development Methodology?
To understand the reasons for this study we need to take a look at the different phases of
the system development methodology and observe where the characteristics of the
RTOS emerge.
Four fundamental development phases come to light:
– Analysis: determines WHAT the system or software has to do;
– Design: HOW the system or software will satisfy these requirements;
– Implementation: DOING IT, i.e. implementing the system or software;
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– Maintenance: USING IT, i.e. using the system or software.
In a waterfall model, one supposes that all these phases are consecutive. In practice, this
is never possible. Most developments end up being chaotic, with all the phases being
executed simultaneously. Adopting a pragmatic approach, the methodology used should
just be a framework to guide producing the correct documents, whilst performing
appropriate reviews and audits at the right time.
13. What Is Bounded Dispatch Time?
When the system is not loaded, there will be just one thread waiting in a ready state to be
executed. With higher loads, there might be multiple threads in the ready list. The
dispatch time should be independent of the number of threads in the list.
In good RTS design, taking into account the thread priorities, the list is organized when
an element is added to the list so that when a dispatch occurs, the first thread in the list
can be taken.
14. What Is The Need For Max Number Of Tasks?
A task, thread or process may be considered as an OS object. Each object in the OS
needs some memory space for the object definition. The more complex the object, the
more attributes it will have, and the bigger the definition space will be. If there is for
example an MMU in the system, the mapping tables are extra attributes for the task and
more system space is needed for all this.
15. Why Min Ram Is Required Per Task?
Memory footprint is an important issue in an embedded system despite the cost
reductions in silicon and disk memory these days. The size of the OS, or the system
space necessary to run the OS with all the objects defined is important. A task needs to
run RAM for the changing parts of the task control block (the task object definition) and
for the stack and heap to be capable of executing the program (which might be in ROM
or RAM).
UNIT V
PART-A
1. When The Error Will Occur When We Use The Semaphore?
i.When the process interchanges the order in which the wait and signal operations on the
semaphore mutex.
ii.When a process replaces a signal (mutex) with wait (mutex).
iii.When a process omits the wait (mutex), or the signal (mutex), or both.
2. Differentiate Counting Semaphore And Binary Semaphore.
Binary Semaphore:
The general-purpose binary semaphore is capable of addressing the requirements of both
forms of task coordination: mutual exclusion and synchronization.
A binary semaphore can be viewed as a flag that is available (full) or unavailable (empty).
Counting semaphores are another means to implement task synchronization and mutual
exclusion.
3. What Is Priority Inheritance?
Priority inheritance is a method for eliminating priority inversion problems. Using this
programming method, a process scheduling algorithm will increase the priority of a process
to the maximum priority of any process waiting for any resource on which the process has a
resource lock.
4. Define Message Queue.
A message queue is a buffer managed by the operating system. Message queues allow a
variable number of messages, each of variable length, to be queued. Tasks and ISRs can
send messages to a message queue, and tasks can receive messages from a message queue
(if it is nonempty). Queues can use a FIFO (First In, First Out) policy or it can be based on
priorities.
5. Define Mailbox And Pipe.
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A mailboxes are software-engineering components used for interprocess communication, or
for inter-thread communication within the same process. A mailbox is a combination of a
semaphore and a message queue (or pipe).
Message queue is same as pipe with the only difference that pipe is byte oriented while
queue can be of any size.
6. Define Socket.
A socket is an endpoint for communications between tasks; data is sent from one socket to
another.
7. Define Remote Procedure Call.
Remote Procedure Calls (RPC) is a facility that allows a process on one machine to call a
procedure that is executed by another process on either the same machine or a remote
machine. Internally, RPC uses sockets as the underlying communication mechanism.
8. Define Thread Cancellation & Target Thread.
The thread cancellation is the task of terminating a thread before it has completed. A thread
that is to be cancelled is often referred to as the target thread. For example, if multiple
threads are concurrently searching through a database and one thread returns the result, the
remaining threads might be cancelled.
9. What Are The Different Ways In Which A Thread Can Be Cancelled?
Cancellation of a target thread may occur in two different scenarios:
¬ Asynchronous cancellation: One thread immediately terminates the target thread is called
asynchronous cancellation.
¬ deferred cancellation: The target thread can periodically check if it should terminate,
allowing the target thread an opportunity to terminate itself in an orderly fashion.
10. What Is Preemptive And Non-Preemptive Scheduling?
Under non-preemptive scheduling once the CPU has been allocated to a process, the process
keeps the CPU until it releases the CPU either by terminating or switching to the waiting
state.
Preemptive scheduling can preempt a process which is utilizing the CPU in between its
execution and give the CPU to another process.
11. What Is A Dispatcher?
The dispatcher is the module that gives control of the CPU to the process selected by the
short-term scheduler. This function involves:
¬ Switching context
¬ Switching to user mode
¬ Jumping to the proper location in the user program to restart that program.
12. What Is Dispatch Latency?
The time taken by the dispatcher to stop one process and start another running is known as
dispatch latency.
13. What Are The Various Scheduling Criteria For Cpu Scheduling?
CPU utilization
Throughput
Turnaround time
Waiting time
Response time
14. Define Throughput?
Throughput in CPU scheduling is the number of processes that are completed per unit time.
For long processes, this rate may be one process per hour; for short transactions, throughput
might be 10 processes per second.
15. What Is Turnaround Time?
Turnaround time is the interval from the time of submission to the time of completion of a
process. It is the sum of the periods spent waiting to get into memory, waiting in the ready
queue, executing on the CPU, and doing I/O.
DEPT OF ECE EC E74 SPREAD SPECTRUM COMMUNICATION
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UNIT -I
PART-A
1. Define Spread spectrum
In telecommunication and radio communication, spread-spectrum techniques are methods by which a
signal (e.g. an electrical, electromagnetic, or acoustic signal) generated with a particular bandwidth is
deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth.
2. What are kasami sequences?
Kasami sequences are binary sequences of length 2N-1 where N is an even integer. Kasami sequences
have good cross-correlation values approaching the Welch lower bound. There are two classes of
Kasami sequences - the small set and the large set.
3. List four beneficial attributes of SS system?
The four attributes are Energy density reduction, Interference suppression, Fine time resolution &
multiple access.
4. What is processing gain?
In a spread spectrum system, the process gain (or 'processing gain') is the ratio of the spread (or RF)
bandwidth to the unspread (or baseband) bandwidth. It is usually expressed in decibels (dB).
5. What are the principal advantages of spread spectrum?
It is a Jam-resistant communication system, it can be used as CDMA radios, the advantages of using
Spread spectrum in cordless Phone include security, immunity to noise, and longer range.
6. What are the types of techniques used for spectrum?
First Generation techniques were AMPS based on FDMA technology, second generation were GSM
based on TDMA technology and third generation purely based on CDMA techniques.
7. Name jamming methods?
There are two different types of jamming methods; they are obvious jamming and Subtle
jamming
8. List out the application of SSC?
It is widely used in military, industrial, avionics, scientific and civil uses etc.
9. What is maximum length sequence?
A maximum length sequence (MLS) is a type of pseudorandom binary sequence. They are bit
sequences generated using maximal linear feedback shift registers and are so called because they are
periodic and reproduce every binary sequence (except the zero vector) that can be represented by the
shift registers (i.e., for length-m registers they produce a sequence of length 2m − 1). An MLS is also
sometimes called an n-sequence or an m-sequence.
10. State the properties of PN code.
A PN sequence has three following properties:
The number of ‘1’s and the number of ‘0’s in a PN sequence are only different by one.
Run lengths of zeroes or ones are the same as in a coin flipping experiment. Half of the run lengths
are unity, one-quarter are of length two, one-eighth are of length three and a fraction 1/2n of all
runs are of length n.
If the sequence is shifted by any non-zero number of elements, the resulting sequence will have an
equal number of agreements and disagreements with the original sequence.
11. Name 3 synchronizations required at spread spectrum receiver.
(i) Correlation interval synchronization
(ii) Spread spectrum synchronization
(iii) Carrier signal synchronization
12. Define the process of spectrum spreading
An RF communications system in which the baseband signal bandwidth is intentionally spread
over a larger bandwidth by injecting a higher frequency signal (Figure 1). As a direct consequence,
energy used in transmitting the signal is spread over a wider bandwidth, and appears as noise.
13. When a sequence is said to be maximal sequence
DEPT OF ECE EC E74 SPREAD SPECTRUM COMMUNICATION
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The input polynomial A(x) and the generator connections polynomial h(x). The maximum period
of the binary sequence generated by the r-stage shift register is limited to 2r−1.Abinary sequence
which achieves this maximum period is called maximal-length sequence or simply m-sequence
14. Give the reasons for use of spread spectrum systems.
i) They aid privacy of the transmission, since the spectral density of the spread spectrum may be less
than the noise spectral density of the receiver.
ii) The de-spreading process in the receiver will spread the spectra of unwanted narrowband signals,
thus improving interference rejection.
iii) The effect on a spread spectrum receiver that receives a spread spectrum from a different spread
spectrum system using the same frequency bands but implementing a different spreading pattern,
approximates to noise in the receiver.
15. What is lockup state?
The maximum number of states for a shift register of length m is 2m, i.e. for a 7-stage shift register 27
= 128 states. However the all-zero state is not allowable as the pseudo-random generator would lock-
up as ex-OR’ing two logic 0 results in yet logic 0 at the input. Therefore a maximal length pseudo-
random code generator can produce a pseudo-random sequence 2m-1 bit long before repeating itself.
This is called as Lock up state
UNIT -II
PART-A
1. What is meant by chernoff bound?
For a given jammer coordinate sequence J, the chernoff bound to the bit error probability is given as,
N-1
Pb(J)≤1/2 exp{-Eb/(2/N ∑ Jk2)}
K=0
This chernoff bound applies for all N and J, assumes the sequence {c (k) is likely to be 1 or -1
2. What is a jammer?
Jamming is the (usually deliberate) transmission of radio signals that disrupt communications by
decreasing the signal-to-noise ratio
3. Write about repeat code?
It transmit the rate of 1/m
K= {d1, d2………….dn}
ai=di
Where i=1, 2, 3……
4. Describe about pulse jammer
Jammer is occurs in the form of pulse over the transmission occurs, then it is known as pulse jammer
5. Draw the block diagram of coherent DSSS transmitter
6. What is partial band noise jammer?
This type of jammer will oppose the particular or selected or partial band. Therefore this type of noise
jamming or jammer is called as partial band noise jammer.
DEPT OF ECE EC E74 SPREAD SPECTRUM COMMUNICATION
C.THIAGARAJAN,AP/ECE Page No:26
7. Define coherent reception?
Coherent reception: when the receiver exploits knowledge of the carrier's phase to detect the signal.
the process is called coherent detection. Non-coherent detection: when the receiver does not utilize
such phase reference information the process is called non-coherent detection.
8. Define BER?
The bit error rate or bit error ratio (BER) is the number of bit errors divided by the total number of
transferred bits during a studied time interval. BER is a unit less performance measure, often
expressed as a percentage.
9. What is noise jammer?
An electronic jammer that emits a carrier modulated with recordings or synthetic reproductions of
natural atmospheric noise; the radio-frequency carrier may be suppressed; used to discourage the
enemy by simulating naturally adverse communications conditions. During World War II, a powerful
transmitter modulated with white noise tuned to the approximate frequency of an enemy transmitter
and used to obscure intelligible output at the receiver.
10. Define BER Probability?
The bit error probability pe is the expectation value of the BER. The BER can be considered as an
approximate estimate of the bit error probability. This estimate is accurate for a long time interval and
a high number of bit errors.
11. What is multitone jammer?
When all the band or tone used to jamming the signal is represented as multitone jammer.
12. What is pulse jammer?
Pulse jammer is nothing but Jamming process is occurs in the form of pulse over the transmission
occurs; therefore it is represented as pulse jammer.
13. Define DSSS
In telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As
with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the
information signal that modulates the carrier or broadcast frequency. The name 'spread spectrum'
comes from the fact that the carrier signals occur over the full bandwidth (spectrum) of a device's
transmitting frequency.
14. What are jammer signals?
Jammer signals are used jam the radio signals the different types of jammer signals are Random
noise, Stepped tones, Spark, Gulls, Random pulse, Wobblers, Recorded sounds & Preamble jamming.
15. Write about repeat code
This type of codes will generate the same code until it executes the new sequence. The expression for
defining the repeat code is,
It transmit the rate of 1/m
K= {d1, d2………….dn}
ai=di
Where i=1, 2, 3…… this type of code is always represented in terms of sequence code.
UNIT -III
PART-A
1. What is the difference between fast and slow hopping
fast hopping slow hopping
Multiple hops are required per symbol Multiple symbols are transmitted per single hop
Usually this type of hopping are faster Usually this type of hopping are slower than fast
hopping
2. Define total hopping bandwidth
The bandwidth of a frequency slot in the hopset is referred as the instantaneous bandwidth B. the
bandwidth over which the frequency hopping occurs is called hopping bandwidth W.
3. Define frequency hop?
DEPT OF ECE EC E74 SPREAD SPECTRUM COMMUNICATION
C.THIAGARAJAN,AP/ECE Page No:27
Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly
switching a carrier among many frequency channels, using a pseudorandom sequence known to both
transmitter and receiver
4. Describe chip rate?
Chip refers to the individual FH/MFSK tone of shortest duration In an FFH system where there are
multiple hops per M-ary symbol, each hop is a chip. In an SSH system, a chip denotes an M-ary
symbol, Chip rate Rc=max (Rh,Rs).
5. What are the characteristics of FH SS system?
FH SS signals are highly resistant to jamming, which means immune to jamming signal. Robust to
noise signal. Therefore these are the some characteristics of FH SS system.
6. What is constellation?
A constellation is defined as an area of the celestial sphere. These areas are grouped around asterisms
which themselves are generally referred to in non-technical language as constellations.
7. What are the characteristics of DS SS?
This type of SS system purely depends on direct sequence instead of frequency hopping method.
Noise and error rate is little bit high when compared to some other type.
8. What is the performance parameter system?
It is defined as the analyzing and determining the performance of the Spread spectrum
communication system. Therefore it is referred as performance parameter system.
9. List the disadvantage of FH system?
Spectrum will be slow when compared to other technique. It will work with frequency alone.
Requires large amount of channel frequency.
10. Define Fast frequency hopping
Coherent demodulation is not possible so, we discuss the system with non coherent demodulation.
The system is said to be fast frequency hopped (FFH), when the hop rate FH is an integer multiple of
the MFSK symbol rate Rs.
11. Define frequency hop
Frequency hopping spread spectrum is the change in frequency with frequency hopping which are as
the symbol of transmitted data.
12. What is the difference between fast and slow hopping?
Fast Hopping: it requires ‘n’ No. of hops in order to required per symbol
Slow hopping: It requires ‘n’ No. of symbols in order to transmit per single hop.
13. What is frequency synthesizer mention its applications.
A frequency synthesizer is an electronic system for generating any of a range of frequencies from a
single fixed time base or oscillator. It is widely used in radio receivers, mobile telephones,
radiotelephones, walkie-talkies, CB radios, satellite receivers, GPS systems, etc.
14. What is slow frequency hopping?
The system is said to slow frequency hopped (SFH), when the MFSK symbol rate RS is an integer
multiple of the hop rate Rh.
15. What are the performances in SS receiver?
In receiver, all the spreaded signals will be reconstructed with various essential things in order to
collect all the spreaded info which was originally transmitted by the transmitter part.
UNIT -IV
PART-A
1. What is a matched filter?
Matched filter is used for the unwanted signal are deleted through this filter. It will reduce the
unwanted noise. This filter will match with the thing which required filtering immediately.
2. Describe Tau-Dither loop?
Tau-Dither loop is a special case of delay locked loop which has only one correlate and it eliminates
the erratic zero control signal by injecting a small error in the tracking loop
3. What is acquisition and tracking?
DEPT OF ECE EC E74 SPREAD SPECTRUM COMMUNICATION
C.THIAGARAJAN,AP/ECE Page No:28
The acquisition problem is one of searching throughout a region of time and frequency uncertainty in
order to synchronize the received spread-spectrum signal with the locally generated spreading signal.
Tracking is done after the acquisition. It is used in both transmitter and receiver the local carrier is
called tracking.
4. Describe Delay locked loop?
In the delayed locked loop, two correlators have been used. This will make a delay to make a loop.
Therefore it is called as delayed locked loop
5. Enumerate the characteristics of FH SS receiver?
Spread-spectrum signals are highly resistant to deliberate jamming, unless the adversary has
knowledge of the spreading characteristics. These are characteristics of FH SS receiver
6. What is the need of synchronization in SS receiver?
In coherent reference, PN sequence and reference carrier is required. Similarly in non coherent
receiver reference carrier is required.
7. What is the need for asynchronization in SS receivers?
Need for asynchronization in SS receivers, coherent reference, PN sequence and reference carrier
is required. Similarly in non coherent receiver reference carrier is required. Therefore these are
necessary things are need in asynchronization in SS receivers.
8. What are the advantages of CDMA in spread spectrum communication?
Efficient practical utilization of the fixed frequency spectrum
Flexible allocation of resources
9. Define synchronization
The process of synchronizing the local and received PN signals is ordinarily accomplished in two
stages. Initially, a coarse alignment of the two PN signals is produced to within a small (typically less
than a fraction of a chip) residual relative timing offset.
10. What is acquisition?
It is defined as the acquisition problem is one of searching throughout a region of time and
frequency uncertainty in order to synchronize the received spread-spectrum signal with the locally
generated spreading signal. Hence it known as acquisition.
11. What is matched filter
The matched filter is the optimal linear filter for maximizing the signal to noise ratio (SNR) in the
presence of additive stochastic noise. Matched filters are commonly used in radar
12. What is acquisition in FHSS receiver
The received signal with mixed locally generated frequency then passed to BPF and then passed to
square law detector and then send it to the delay N-1 hop and then to passed comparator to produce
the output.
13. Describe DLL.
DLL is defined as the two correlators have been used. This will make a delay to make a loop.
Therefore it is called as delayed locked loop
14. Define coherent detection
A coherent detection is the conversion of the intermediate frequency signal in a Doppler radar to I and
Q channels. This signal is converted so that the phase of the echoes produced is preserved.
15. What is rapid acquisition
Rapid acquisition by sequential estimation (RASE), system enters its best estimate of the first n
received code chips into the n stages of its local PN generator. The fully loaded register defines a
starting state from which the generator begins its operation.
UNIT -V
PART-A
1. What are the satellite communication characteristics?
This communication comes under the category of wireless communication. It widely uses the
uplink and downlink frequency. The coverage range is extremely larger when compared to other
communications systems.
2. Write the working principle of CDMA?
DEPT OF ECE EC E74 SPREAD SPECTRUM COMMUNICATION
C.THIAGARAJAN,AP/ECE Page No:29
CDMA is an example of multiple access, which is where several transmitters can send information
simultaneously over a single communication channel. This allows several users to share a band of
frequencies (see bandwidth). To permit this to be achieved without undue interference between the
users, CDMA employs spread-spectrum technology and a special coding scheme
3. Give two advantages of spread spectrum?
The several advantages of Spread spectrum are WLAN and High resolution ranging and CDMA
radio.
4. What is multi path interference?
Multipath interference is a phenomenon in the physics of waves whereby a wave from a source
travels to a detector via two or more paths and, under the right condition; the two (or more)
components of the wave interfere.
5. What are the concepts of CDMA?
In code division multiple access (CDMA) systems, the narrowband message signal is multiplied
by a very large bandwidth signal called the spreading signal. The spreading signal is a pseudo-noise
code sequence that has a chip rate which is orders of magnitudes greater than the data rate of the
message.
6. What are the different application of SSC
It is widely used in military, industrial, avionics, scientific and civil uses etc.
7. List the potential application of SSC
It is majorly used in the place where secret communication is required, a strong secure
communications may be implemented by the usage of SSC. Therefore US military systems were first
used the spread spectrum communications system.
8. What is the acquisition in FH SS receiver?
The received signal with mixed locally generated frequency then passed to BPF and then passed
to square law detector and then send it to the delay N-1 hop and then to passed comparator to produce
the output.
9. What is anti jam military communication
One of the key applications of spread spectrum is for anti jam communications in a hostile
environment. The basic mechanism by which a DSSS receiver attenuates a noise jammer.
10. What are the benefits offered by spread spectrum for satellite communication
Secure communication, DTH, Cellular mobile communication, weather forecasting, military
purpose and unknown planets details exploration etc.
11. What is the purpose of radiometer?
A radiometer or roentgen meter is a device for measuring the radiant flux (power) of
electromagnetic radiation. Generally, the term radiometer denotes an infrared radiation detector or
Ultraviolet detector yet it also includes detectors operating on any electromagnetic wavelength.
12. State the need of IS 95
IS abbreviates for Interim Standard 95. This standard employs direct sequence spread spectrum in
order to provide dramatically higher capacity when compared to existing analog systems.
13. List the different types of interference
There are two different types of interference are available they are, Constructive Interference and
destructive interference
14. What is cell breathing?
In CDMA-based mobile telephone systems, cell breathing is a mechanism which allows
overloaded cells to offload subscriber traffic to neighboring cells by changing the geographic size of
their service area. Heavily loaded cells decrease in size while neighboring cells increase their service
area to compensate. Thus, some traffic is handed off from the overloaded cell to neighboring cells,
resulting in load balancing
15. State about GPS
The Global Positioning System (GPS) is a space-based satellite navigation system that provides
location and time information in all weather conditions, anywhere on or near the Earth where there is
an unobstructed line of sight to four or more GPS satellites.
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