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Communications Reviewer November 2006

TELEVISION

Question:“The keystone effect produces a square

raster”- it is a ___ statement. Answer: false

Question:The width of a vertical sync pulse with its

serrations includes the time of Answer: six half lines or three lines

Question:Sawtooth generator circuits produce the

scanning raster, but the sync pulses areneeded for

Answer: timing

Question:“31,500 Hz for the vertical scanning

frequency” is a ____ assertion. Answer: wrong

COLOR TELEVISION: CIRCUITS AND

SIGNALS

Question:Brightness variations of the picture

information are in the ___ signal. Answer: Y or luminance

Question:The hue 180 degrees out of phase with red

is Answer: cyan

Question:Greater peak to peak amplitude of the 3.58

MHZ chrominance signal indicates more _____. Answer: saturation

Question:The interfering beat frequency of 920 kHz is

between the 3.58 MHz color subcarrier and the Answer: 4.5 MHz intercarrier sounds

ECE Board November 2005Question:

The hue of color sync phase is Answer:

yellow-green

Question:___ signal has color information for 1.3 MHz

bandwidth. Answer: I

Question:“A fully saturated color is mostly white” – it

is a ____ statement. Answer: false

Question:The color with the most luminance is

Answer: yellow

Question:The hue of a color 90 degrees leading sync

burst phase is Answer: cyan

Question:The average voltage value of the 3.58 MHZ

modulated chrominance signal is the Answer: brightness of the color

Question:AC video signal drive is varied by the

Answer: contrast

Question:The input signal for the video amplifier is

supplied by the Answer: video amplifier

Question:The video amplifier bandwidth in a

monochrome receiver is generally Answer:

3.2 MHZ

Question:The dc component of the video signal

determine the Answer: brightness

Question:

Prepared by: Engr. Divino Fiel de Bien, E.C.E. Page 1of 33

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What method is used to preserve the dccomponent?

Answer: direct coupling

Question:The frequency of the second IF signal when

the receiver is tuned to UHF channel 14 is Answer: 4.5 MHz

Question:The maximum frequency deviation of the

FM associate sound signal is Answer: 25 kHz

Question:The ____ is the main source of the receiver

noise. Answer: mixer

Question:A break in the ____ can cause the symptom

of no picture on a clean raster without snow. Answer: IF section

Question:A break in the ____ can cause the symptom

of no picture but with snow. Answer: antenna circuit

Question:A/an ______ is usually out of sync.

Answer: overload picture

Question:A TV monitor does not have an ____.

Answer: RF tuner

Question:The standard level of composite video

signal for connections between modular units

is Answer: 1 Vp-p

Question:A ___ voltage supply for the picture tube is

included in the TV monitor. Answer: high

RASTER CIRCUITS AND SYNC

Question:All the sync pulses have ____ amplitude

Answer: the same

Question:The ____ pulse has the lowest frequency

Answer: V sync

Question:The sync separator is a

Answer: common emitter amplifier

Question:The _____ includes all the sync pulses.

Answer: separated sync

Question:The input for the V integrator is taken from

the ______. Answer: sync separator

Question:The separated sync is _____ from the pulses

in the composite video signal. Answer: inverted

Question:The output from the RC integrator is the

voltage across ____. Answer: CQuestion:

A typical time constant for the verticalintegrator is ____

Answer:

50 µ s

Question:

A single bright line across the center of thescreen can be caused by

Answer: failure of the oscillator or amplifier or a defect in the coupling circuits or yoke

Question:Too much black space at the bottom of the

screen can be caused by ____ Answer:


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weak vertical output

Question:The _____ on the vertical amplifier affects

the height and linearity of the raster. Answer: dc bias

Question:The diagonal black bar represents

Answer: H scanning

Question:_____ control makes the picture stop rolling.

Answer: V-hold

Question:HAFC or horizontal AFC is a

Answer: PLL

Question:HAFC is for the

Answer: horizontal sync

Question:Horizontal flyback is for

Answer: high voltage

Question:The output stage operates similar to

Answer: class C amplifier

Question:The ____ system is used in television

cameras and other studio equipment toprovide the V and H drive signals. It providesexcellent interlacing.

Answer: gen-lock

Question:The whole gen-lock circuit can be contained

in _____ dedicated chip. Answer: one

Question:The master oscillator operates at

Answer: 31.5 kHz

Question:

No ___ hold is used. Answer: vertical

Question:For the TV supply, the Tripler is for

Answer: high voltage

Question:For the TV power supply, the voltage

regulator is used for the Answer: line rectifier

Question:___ results in a total loss of the raster since

the flyback high voltage depends on thehorizontal output.

Answer: no horizontal output

COLOR TELEVISION RECEIVER CIRCUITS

Question:The Y signal produces a ____.

Answer: monochrome picture

Question:The drive controls are adjusted for ____.

Answer: white

Question:

Color ___ generally does not have a drivecontrol.

Answer: red

Question:When the blue gun is dead, the

monochrome picture and raster will be Answer: yellow

Question:A monochrome picture can be produced

Answer: without the 3.58 MHZ chroma section

Question:An open in the _____ output-adder stage

results in a magenta picture. Answer: green

Question:


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The value of the beat frequency betweenthe associated sound carrier and colorsubcarrier is

Answer: 920 kHz

Question:The beat frequency between the associated

sound carrier and the picture carrier is ____. Answer: 4.5 MHZ

Question:The relative gain for 42.17 MHz in the IF

amplifier is Answer: 50 %

Question:The bandpass amplifier is tuned to 3.58

MHz with a typical bandwidth of ____. Answer: +/- 0.05 MHz

Question:The ____ control varies the gain of the

bandpass amplifier. Answer: color

Question:The _____ is on during H flyback time.

Answer:

burst amplifier

Question:A _____ needs two input signals.

Answer: synchronous demodulator

Question:The _____ provides dc color voltage for the

color oscillator. Answer: AFPC circuit

Question:The ____ control adjusts for the phase angle

for the demodulated color video signals. Answer: tint

Question:Circuits that can cause the trouble of no

color are Answer:

bandpass amplifier, color oscillator, and color killer

Question:A fixed phase error in the color oscillator

causes Answer: wrong hues

Question:The R-Y demodulator fails. Colors ___ and

___ will be missing from the picture Answer: red, cyan

Question:The ACC circuit varies the gain of the ____

Answer: first BPA

Question:The manual color control varies the

amplitude of the _____ chroma signal. Answer: 3.58 MHZ

Question:The output from the BPA feed the

Answer: demodulators

Question:The burst amplitude used to determine the

Answer:

ACC bias

Question:The color killer is on the

Answer: BPA

Question:____ is used to produce the dc bias from the

color killer diode detector. Answer: burst

Question:Color snow or confetti is predominantly

____. Answer: magenta

Question:The angle between R-Y and B-Y is


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Answer: 90 degrees

Question:The bandwidth of the I signal is

Answer: 1.3 MHz

Question:DC coupling used for the ____ output.

Answer: demodulator

Question:The crystal ringer is shock-excited by ___.

Answer: color burst

Question:In an AFPC phase detector, the ____ and ___

cw signals are 90 degrees out of phase. Answer: burst, oscillator

Question:The burst separator is ___ during horizontal

trace line. Answer: off

Question:______ means that colors drift through the

picture. Answer: no color sync

Question:The superband channel number just above

VHF broadcast channel 13 is Answer: 23

Question:VHF broadcast channel does a TV receiver

with a cable converter stay tuned at Answer: 2, 3, or 4

Question:The ___ conductor of coaxial cable serves as

a shield. Answer: outer

Question:Generally ____ cable is used for the drop

line. Answer:

RG-59U

Question:Thinner cable has _____ losses.

Answer: greater

Question:The value of R that was used to terminate

Rg-59U coaxial cable for impedance matchingis

Answer: 75 ohms

Question:A line with more C per unit length has a

lower ____. Answer: Zo

Question:Open ends of transmission line correspond

to a _____ resonant circuit. Answer: parallel

Question:The value of the VSWR when a cable is

terminated in its Zo is Answer: 1.0

Question:Cable losses increases at ____ frequencies.

Answer: higher

Question:Coaxial cables have ____ losses.

Answer: I2R

Question:A ___ loss reduces the signal level by one-

half. Answer: 6 dB

Question:

The _____ of a cable system is the startingpoint of cable signals.

Answer: head-end

Question:A ____ is the main line for cable signals.

Answer: trunk cable


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Question:The insertion loss is ____ than the tap loss

for line taps. Answer: lower

Question:A ____ is used to match the 75 ohms coaxial

cable to the 300 ohms receiver input. Answer: balun

Question:The reference level for the dBmV unit is

____. Answer: 1 mV

Question:The signal level of 2 mV in dBmV units is

Answer: 6 dBmV

Question:The signal level of 0.5 mV in dBmV units is

__. Answer: -6 dBmV

Question:Sync and blanking bars from another

channel can be caused by _____. Answer: overload distortion

Question:

Losses increase with higher _____. Answer: temperature

Question:A slope-control circuit increases the

amplifier gain for ___-frequency channels. Answer: higher

Question:In two-way cable systems, the ____ for

downstreams and upstream signals. Answer: same cable

Question:The upstream signal is in the band of _____.

Answer: 5 to 30 MHz

Question:

The polling signal is in the band of Answer: 107 to 119 MHz

Question:The cable converter uses ___ local

oscillators. Answer: two

Question:The video IF carrier in a cable converter is

generally Answer: 612.75 MHz

Question:The local oscillator for the up converter

operates in the ___ range. Answer: UHF

Question:Each cable channel is selected by setting

the frequency of the ___ for the up converter.

Answer: VCO

Question:Wave traps to attenuate premium channels

are usually located ___. Answer: in the feed line to each subscriber

Question:

A scrambled channel usually has a ____ , asevidenced by rolling and diagonal bars.

Answer: picture that is out of sync

Question: A scrambled channel needs _____ pulses to restore the sync.

Answer: decoding

Question:_____ have the cable channels that are

heterodyned down to lower frequencies. Answer: supertrunks

Question:The frequency of 13 GHz is in the ____ band

Answer:


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microwaveQuestion:

_____ can be used for microwave links fortelevision.

Answer: FM

Question:______ cable has very low losses.

Answer: fiber optics

Question:____ means the bending of light waves.

Answer: refraction

Question:______ cables makes use of internal

reflections of light. Answer: fiber optic

Question:Typical index of refraction for glass

Answer: 1.8

Question:Typical index of refraction for diamond

Answer: 2.4

Question:Typical index of refraction for water

Answer:

water

TELEVISION AND VIDEO SERVICING

Question:An ____ transformer has separate primary

and secondary windings. Answer: isolation

Question:The ______ blade in a polarized AC line plug

connects to the chassis in the receivers with aline operated half-wave rectifier.

Answer: wider

Question:______ has higher resistance as a DC

voltmeter. Answer: DMM

Question:Meter loading ______ the voltage reading.

Answer: decreases

Question:The external multiplier for a high voltage

probe is Answer: 900 megaohms

Question:The TV switch on an oscilloscope can be set

for ______ cycles of video signal, at either theV or the H scanning rate.

Answer: two

Question:A _______ oscilloscope has a CRT with two

electron guns. Answer: dual-beam

Question:A delayed sweep oscillator uses ________

internal time bases. Answer: two

Question:A _______ produces the IF output signal.

Answer: tuner subber

Question:The NTSC ________ produces standard

chroma and luminance values. Answer: color-bar generator

Question:The color bars in a gated rainbow pattern

differ in hue phase by Answer: 30 degrees

Question:

Color bars have the standard amplitude of Answer: 75 IRE units

Question:The range of the tint control when it can

move a color one bar to the left and right is Answer: +/- 30


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Question:Which color difference signal has the same

phase as the burst? Answer: B-Y

Question:Which color bar has the output from a B-Y

demodulator? Answer: 6th

Question:No horizontal output _____

Answer: can kill the sound

Question:A receiver with current in the ADG coils has

______ Answer: AC power input

Question:Two pairs of horizontal bars are produced

by Answer: 120 Hz ripple in the video signal

INTRODUCTION TO RADAR

FUNDAMENTALS

Question:Radar is an acronym made up of the words

______. Answer:Radio detection and ranging

Question:What term is used to refer to electronicequipment that detects the presence,direction, height, and distance of objects byusing reflected electromagnetic energy?

Answer:Radar

BASIC RADAR CONCEPTS

Question:Radar uses electromagnetic energy pulses.

The radio-frequency (rf) energy is transmittedto and reflects from the reflecting object. Asmall portion of the energy is reflected andreturns to the radar set. This returned energyis called a(n) _____.

Answer:

Echo

Question:Radar surface angular measurements arenormally made in a clockwise direction from

_______ or from the heading line of a ship oraircraft.

Answer: True north

Question:In radar surface angular measurement, thesurface of the earth is represented by animaginary flat plane, tangent (or parallel) tothe earth’s surface at that location. This planeis referred to as the_____.

Answer: Horizontal plane

Question:In radar surface angular measurements, allangles in the up direction are measured in asecond imaginary plane that is perpendicularto the horizontal plane. This second plane iscalled the ______.

Answer:Vertical plane

Question:What name is given to the line made

directly from the radar set to the object? Answer Line of sight (LOS)

Question: The length of LOS is termed _____.

Answer:Range

Question:How is the angle between the horizontal planeand the LOS known?

Answer:Elevation angle

Question: The angle measured clockwise from true northin the horizontal plane is referred to as the

______.

Answer: True bearing or Azimuth angle

Question:What coordinates are used to describe thelocation of an object with respect to the radarantenna?

Answer:Range, bearing, and elevation


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Question:Radar surface-angular measurements arereferenced to true north and measured in whatplane?

Answer:Horizontal plane

Question: The distance from a radar set to a targetmeasured along the line of sight is identifiedby what term?

Answer:Range

RANGE

Question:Electromagnetic energy travels through air atapproximately the speed of light, which is

Answer:186,000 statute miles per second or 162,000nautical miles or 984 feet per microsecond or328 yards per microsecond

Question:Radar timing is usually expressed in what unitof time?

Answer:Microseconds

Question: This type of radar set transmits a short burst of electromagnetic energy in order to measuretarget range which is determined by

measuring elapsed time while the pulse travelsto and returns from the target.

Answer:Pulsed radar

Question:Because two-way travel is involved, a totaltime of 12.36 (6.18 x 2) microseconds pernautical mile will elapse between the start of the pulse from the antenna and its return tothe antenna from a target. This 12.36microsecond time interval is sometimesreferred to as a _________.

Answer:Radar mile, radar nautical mile or nauticalradar mile

Question:If the elapsed time for an echo is 62microseconds, then the distance is____.

Answer: 5 miles

MINIMUM RANGE

Question: The _____ alternately switches the antennabetween the transmitter and receiver so thatonly one antenna need be used.

Answer:Duplexer

Question: Timing of this switching action is critical to theoperation of the radar system. The minimumrange ability of the radar system is alsoaffected by this timing. Important factors inthis duplexer switching action are _____.

Answer:

Pulse width and recovery time

Question: The _____ edge of the transmitted pulse causesthe duplexer to align the antenna to thetransmitter. This action is essentiallyinstantaneous.

Answer:Leading

Question: The _____ edge of the pulse causes theduplexer to line up the antenna with thereceiver; however, this action is notinstantaneous.

Answer: Trailing

MAXIMUM RANGE

Question: The maximum range of a pulse radar systemdepends upon

Answer:Carrier frequency, peak power of thetransmitted pulse, pulse repetition frequency(PRF), or pulse repetition rate (PRR), andreceiver sensitivity

Question: The primary limiting factor for the maximumrange of a pulse radar system is the

Answer:Pulse repetition frequency (PRF)

Question:What determines the maximum range thepulse can travel to a target and still return ausable echo?

Answer:Peak power of the pulse


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Question: ______ is the smallest signal detectable by areceiver system that can be processed andpresented on an indicator.

Answer:A usable echo

Question: The frequency of the rf energy in the pulseradiated by a radar is referred to as the _____ of the radar system.

Answer:Carrier frequency

Question: The carrier frequency is often a limiting factorin the maximum range capability of a radarsystem because radio frequency energy above

_____ is rapidly attenuated by the atmosphere. Answer:3 GHz

Question: The number of pulses radiated in one second iscalled the

Answer:Pulse-repetition frequency (PRF) or the pulse-repetition rate (PRR)

Question: The time between the beginning of one pulseand the start of the next pulse is called

Answer:Pulse repetition time (PRT)

AMBIGUOUS RETURNS

Question: The radar timing system must be reset to zeroeach time a pulse is radiated. This is to

Answer:Ensure that the range detected is measuredfrom time zero each time

Question: The prt of the radar becomes important inmaximum range determination because targetreturn times that exceed the prt of the radar

system appear at incorrect locations (ranges)on the radar screen. Returns that appear atthese incorrect ranges are referred to as

Answer:Ambiguous returns or secondary-sweepreturns

Question:What is the speed of electromagnetic energytraveling through air?

Answer:Approximately the speed of light (162,000nautical miles per second)

Question:How much time is required for electromagneticenergy to travel 1 nautical mile and return tothe source?

Answer:12.36 microseconds

Question:In addition to recovery time, what determinesthe minimum range of a radar set?

Answer:Pulse width

PULSE-REPETITION FREQUENCY AND

POWER CALCULATIONS

Question: The energy content of the pulse is equal to the ______ of the pulse multiplied by the pulsewidth.

Answer:Peak (maximum) power level

Question:Meters used to measure power in a radarsystem do so over a period of time that islonger than the pulse width. For this reason,pulse-repetition time is included in the powercalculations for transmitters. Power measuredover such a period of time is referred to as

Answer:Average power

Question: The product of pulse width (pw) and pulse-repetition frequency (prf) in the above formulais called the ______ of a radar system.

Answer:Duty cycle

Question:What do we call the ratio of the time on to thetime off of the transmitter?

Answer:Duty cycle

ANTENNA HEIGHT AND SPEED

Question:

Prepared by: Engr. Divino Fiel de Bien, E.C.E. Page10 of 33

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Assume antenna height to be 64 feet, the radiohorizon for this antenna in nautical miles is

Answer:10 nautical miles (nmi)

Solution:

nmi106425.1)ft(h25.1)nmi(d ===

Question:Atmospheric interference with the travel of

electromagnetic energy increases with what rf energy characteristic?

Answer:Frequency

Question:How is prt related to prf?

Answer:PRT is the reciprocal of PRF.

Question:What type of radar transmitter power ismeasured over a period of time?

Answer:Average power

Question:What term is used to describe the product of pulse width and pulse-repetition frequency?

Answer:Duty cycle

BEARING

Question: The ______ of a radar target is the angle

between true north and a line pointed directlyat the target.

Answer: True bearing (referenced to true north) orazimuth angle

Question: True bearing is measured in the ____ plane andin a _____ direction from true north.

Answer:Horizontal, clockwise

Question:

The bearing angle to the radar target may alsobe measured in a clockwise direction from thecenterline of your own ship or aircraft and isreferred to as the _________.

Answer:Relative bearing

ALTITUDE

Question:

Many radar systems are designed to determineonly the range and bearing of an object. Suchradar systems are refrred to by what term?

Answer: Two-dimensional radars (search radars)

Question: These radar systems function as early-warningdevices searching a fixed volume of space.

Answer:2D radar (search radar)

Question:How do we call a search radar system thatdetects altitude as well as range and bearing?

Answer: Three-dimensional (3D) radar

Question:Altitude- or height-finding search radars use abeam that is

Answer:very narrow in the vertical plane

Question:Height-finding radar systems that alsodetermine bearing must have a beam that is

Answer:very narrow in both the vertical and horizontalplanes

Question: _______ scanning permits automaticcompensation for an unstable radar platform(site), such as a ship at sea. Error signals areproduced by the roll and pitch of the ship and

are used to correct the radar beam to ensurecomplete elevation coverage.

Answer:Electronic

Question:What type of scanning technique do weapons-control and tracking radar systems commonlyuse?

Answer:Mechanical elevation scanning

Question:

Most electronically scanned radar systems areused as _____ radars.

Answer:Air search

Question:What type of target bearing is referenced toyour ship?

Answer:Relative bearing


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Question:What type of radar detects range, bearing, andheight?

Answer: Three-dimensional

Question:What characteristic(s) of radiated energy is(are) altered to achieve electronic scanning?

Answer:Frequency or phase

TARGET RESOLUTION

Question:It is the ability of a radar to distinguishbetween targets that are very close together ineither range or bearing.

Answer: Target resolution

Question: ____ radar, which requires great precision,should be able to distinguish between targetsthat are only yards apart.

Answer:Weapons-control

RANGE RESOLUTION

Question: ______ is the ability of a radar system todistinguish between two or more targets on

the same bearing but at different ranges. Answer:Range resolution

Question: The degree of range resolution depends on Answer: The width of the transmitted pulse, the typesand sizes of targets, and the efficiency of thereceiver and indicator

Question:Which is the primary factor in range

resolution? Answer:Pulse width

Question:A well-designed radar system, with all otherfactors at maximum efficiency, should be ableto distinguish targets separated by

Answer:One-half the pulse width time

Question:If a radar system has a pulse width of 5microseconds, determine the range resolution.

Answer:820 yardsSolution:

( ) ( )

yards820164x5

164xsPWyardsresolutionranges

yards

==

µ=µ

BEARING RESOLUTION

Question:How is the ability of a radar system to separateobjects at the same range but at differentbearings known?

Answer:Bearing (azimuth) resolution

Question: The degree of bearing resolution depends on Answer:Radar beam width and the range of the targetsQuestion:Because the radar beam spreads out as rangeincreases, _____ becomes a factor in bearingresolution.

Answer:Range

Question:A radar beam is defined in width in terms of

______. Answer:Half power points

Question:All the points off the centerline of the beamthat are at one-half the power level at thecenter are plotted to define _____.

Answer:Beam width

Question:When the half-power points are connected tothe antenna by a curve the resulting angularwidth of the curve is called the _____.

Answer:Antenna beamwidth

Question:


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What determines the beamwidth of a radarantenna?

Answer: The physical size and shape of the antenna

Question:Radar antenna beamwidth can vary from

Answer:About 1 degree up to 60 degrees

Question: Two targets at the same range must beseparated by ______ to be distinguished as twoobjects.

Answer:At least one beam width

RADAR ACCURACY

Question:It is a measure of the ability of a radar systemto determine the correct range, bearing, and,in some cases, height of an object.

Answer:Radar accuracy

Question: The degree of accuracy is primarily determinedby the ____ of the radar system.

Answer:Resolution

PULSE SHAPE

Question:What is the ideal pulse shape?

Answer:A square wave having vertical leading andtrailing edges

Question:A ______ extends the width of the transmitterpulse, although it may add very little to thetotal power generated.

Answer:Sloping trailing edge

Question:A _____ affects minimum range as well asrange accuracy since it provides no definitepoint from which to measure elapsed time onthe indicator time base.

Answer:Sloping leading edge

Question:

Using a starting point at the lower edge of thepulse’s leading edge would increase ______.

Answer:Minimum range

ATMOSPHERIC CONDITIONS

Question:Electromagnetic wavefronts travel throughempty space in straight lines at the speed of light, but the _____ of the atmosphere affectsboth the travel path and the speed of theelectromagnetic wavefront.

Answer:Refractive index

Question:In the atmosphere, the speed of theelectromagnetic wave is affected by

Answer: Temperature, atmospheric pressure, and theamount of water vapor presentQuestion:It is the bending of electromagnetic wavescaused by a change in the density of themedium through which the waves are passing.

Answer:Refraction

Question:It indicates the degree of refraction, or bendingof electromagnetic waves caused by differentsubstances in the atmosphere.

Answer:Index of Refraction

Summary on MicrowaveCommunications

Question:What is the frequency range of microwaves?

Answer: 300 MHz to 300 GHz

Question:Which of the common frequency bands (HF,VHF, UHF, SHF, etc.) are in the microwaverange?

Answer: UHF, SHF, EHF

Question:What types of communication systems liebelow the microwave band?


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Answer: AM broadcast radio; shortwave radio; FMbroadcast radio; VHF TV; mobile radio

Question:What is the wavelength at the low frequencyend of the microwave band?

Answer: 1 m

Question:What is the wavelength at the middle of themicrowave band?

Answer: 3 cm

Question:What is the wavelength at the high end of themicrowave band?

Answer: 1 mm

Question: Types of microwave communication systems atwhich it operates

Answer: UHF TV 600 MHz Microwave relay 3.9 GHz Satellite communication 6 GHz (up)

4 GHz (down)Troposcatter communication 2 GHz Mobile radio 900 MHz Telemetry 2 GHz

Question:What two problems prevent conventionalelectronic equipment from working atmicrowave frequencies?

Answer: Lead Reactance and Transmit Time

Question:What are the three types of microwavetransmission lines?

Answer: Coaxial cable; stripline; waveguide

Question:What is the maximum power that can beobtained from a microwave semiconductor at10 GHz?

Answer: 10 W

Question:

What is the maximum power that can beobtained from a microwave tube at 10 GHz?

Answer: 500 kW

Question:What are the five types of microwave tubes?

Answer: Klystron; coupled-cavity TWT; helix TWT;Gridded tube; CFA

Question:How much microwave power is received by a3-m2 antenna of the electric field at theantenna is 10-5 V/m and the magnetic field is2.6 x 10-8 A/m?

Answer:0.78 pW Solution::

5 8

2

13

Power Electric Field x Magnetic Field

x Antenna Area

10 V / m x 2.6 x 10 A / m

x 3 m

7.8 x 10

0.78 pW

− −

−

=

=

==

Question:A perfect termination for a transmission line

Answer:Termination (load)

Question:A component that samples the microwavesignal traveling in one direction down a

transmission line Answer:Directional Coupler

Question:A component that combines microwave signalsfrom separate transmission lines into onecommon transmission line and allows nocoupling between the separate lines

Answer:Combiner

Question:

A component containing ferrite material thatallows microwave signals to pass in onedirection through the component, but absorbsmicrowave signals passing in the otherdirection.

Answer:Isolator

Question:


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Given a transmission line of cross section 2 cmby 1 cm (approximately the size of awaveguide operating at 10 GHz), E = 50 V/mand H = 1 A/m. Find the impedance, powerdensity and the total power.

Answer:

Impedance = 50 Ω ; Power density = 2 50W / m ;

Power = 10 mW Solution::

E 50 V / mZ 50 ΩH 1 A / m

= = =

2

2

Power Density E x H

50 W /m x 1 A/ m

50W / m

Power Power Density x Cross sec tional area

50 W / m x 0.02 m x 0.01 m

10 mW

=

=

=

= −

=

=

Question: The receiving antenna of a microwave relay

system has an area of 2m2, E = 377 µV / m,

and H = 1 µA / m. Find the impedance, powerdensity, and total power received by theantenna.

Answer:Impedance = 377 Ω ; Power density =

−10 2 3.77 x 10 W / m ; Power = 754 pW

Solution::

E 377μV / mZ 377Ω

H 1 A / m

= = =

10 2

10 2 2

12

Power Density E x H

377μV /m x 1 A / m

3.77 x 10 W / m

Power 3.77 x 10 W / m x 2 m

7541 x 10 W

754 pW

−

−

−

==

=

=

==

Question:

If two equal microwave signals are added,what is the total signal if (a) the signals are in

phase (phase difference of 0°), (b) 180° out of phase, (c) 270 ° out of phase, and (d) with a

phase difference of 360°? Answer:(a) 2 ; (b) 0 ; (c) 1.416 ; (d) 2Solution::

(a) the signals are in phase so their totalstrength is simply the sum of theirindividual strengths: 1 + 1 = 2.

(b) for a 180° phase difference, one signalreaches its maximum when the otherreaches its minimum. Hence, the signalscancel; 1 – 1 = 0.

(c) for a 270° phase difference, the vectorsum of the signals is taken + = =1 1 2 1.416

(d) when the phase shift is 360°, the signalsare again in phase, 1 + 1 = 2.

Question:A 1-GHz microwave signals moves from point 1to point 2, distance of 3 cm. What is the phasedifference between the points?

Answer:

36°

Solution:: The phase difference is the time required forthe signal to travel between points divided its

period. Thus,

( ) ( )10

9

10

9

Travel timePhase difference x 360

Period

Distance / Velocityx 360

1/ frequency

3 cm 3 x 10 cm / sx 360

1/ 10 s

10x 360

10

36

−

−

= °

= °

= °

= °

= °

Therefore, in traveling 3 cm (slightly more than1 in.), an electromagnetic wave with afrequency of 1 GHz undergoes a 36° phaseshift.

Question: The frequency of the ac power lines in theUnited States is 60 Hz. The typical distancebetween a household and the power plant is10 km (6 mi).What is the phase shift betweenthe household and the plant?

Answer:

0.7°

Solution::21

Period at 60 Hz 1.6 x 10 s60

−= =

3

8

5

10 x 10 mTimefor signalto travelbetweenpoints

3 x 10 m / sec

3.3 x 10 s−

=

=


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5

2

3.3 x 10Phase Shift x 360

1.6 x 10

0.7

−

−= °

= °

The 0.7° phase shift is insignificant and can beignored.

Question:If 10% of the microwave power is reflected atthe mismatch, find the return loss, reflectioncoefficient, and SWR.

Answer:Return loss = 10 dB ; reflection coefficient =0.32 ; SWR = 1.92

Solution::

Re flected power Re turn loss 10log

Incident power

10log0.10 10 dB

=

= =

Re flected power Re flection coefficient

Incident power

0.10 0.32

1 0.33SWR 1.92

1 0.33

=

= =

+= =

−

Question:If the return loss is 20 dB, find the percentreflected power, reflection coefficient, andSWR.

Answer:Reflected power = 1% ; Reflected coefficient =0.1 ; SWR = 1.2

Solution::Re turn loss

%Re flected power Inverse log10

Inverse log2

0.01 1%

Re flected power Re flected coefficient

Incident power

0.01 0.1

1 0.1 1.1SWR 1.2

1 0.1 0.9

= −

== =

=

= =

+= = =−

Question:Design a 50-Ω stripline using 0.03-in.-thick

Teflon fiberglass (ε = 2.55). Determine theguide wavelength at 3 GHz.

Answer:6.26 cmSolution::

( ) ( )

0

0g

Zε 50 2 .55 79.8 Ω

w0.75

b

w 0.75 2 x 0.03 0.045 in.

Then,

λλ

ε

10 cm

2.55

6.26 cm

= =

=

= =

=

=

=

Question:A satellite downlink has a frequency of 4 GHz,a bandwidth of 40 GHz, and uses a cryogenicparamp receiver. Find the power of thereceived signal to maintain a SNR of 20 dB.

Answer:1.8 pW Solution::

Antenna Noise Noise Power Density x Bandwidth

0.00015 pW /MHz x 40 MHz0.006 pW

=

=

=

Reciever Noise Noise Power Density x Bandwidth

0.0003 pW / MHz x 40 MHz

0.012 pW

=

=

=

Then,Total Noise Antenna Noise Reciever Noise

0.006 0.012

0.018 pW

= +

= +

=

Since the signal-to-noise ratio must be 20 dBfor satisfactory operation of the satellitesystem, the received signal must be 100 timesgreater than the noise:

RXP 100 x 0.018 pW

1.8 pW

=

=

Question:Calculate the noise power for (a) a terminationtemperature of 290° K and a bandwidth of 1

MHz and (b) a temperature of 145°K and a 10

MHz bandwidth. Answer:(a) -114 dBm ; (b) -107 dBm

Solution::(a)


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( ) ( ) ( )14

12

N kTB

1 .38 x 10 m W / K MHz 290 K 1 M Hz

4 x 10 mW

114 dBm

−

−

=

= ° ⋅ °

=

= −

(b)

( ) ( ) ( )14

12

N kTB

1.38 x 10 mW / K MHz 145 K 10 MHz

20 x 10 mW

107 dBm

−

−

=

= ° ⋅ °

=

= −

Question:A satellite downlink is operating at 10 GHz witha 40-MHz bandwidth. It has a cryogenicparamp receiver. What received power isneeded to achieve a signal-to-noise of 20 dB?

Answer:-88 dBmSolution::

antenna

paramp

T 10 K

T 20 K

= °

= °

Therefore,

totalT 10 K 20 K 30 K= ° + ° = °

So the noise power is

( ) ( ) ( )14

N kTB

1.38 x 10 mW / K MHz 30 K 40 MHz

108 dBm

−

=

= ° ⋅ °

≈ −

Therefore,Recieved Power 108 dBm 20 dB 88 dBm≈ − + ≈ −

Question:An amplifier has a gain of 40 dB and a noise-figure of 3 dB. The input signal (S in) is -80 dBm,and the bandwidth is 10 MHz. Find SNRin andthe SNRout.

Answer:SNRin = 24 dB ; SNRout = 21 dBSolution::

The noise generated by the input signal

source depends on its temperature, whichfor most applications is 290 °K(roomtemperature). In a 1-MHz band, the noisepower is -114 dBm. In a 10-MHz bandwidth,noise power is 10 dB greater, so here N =-104 dBm. Hence

( )inSNR 180dBm 104 dBm 24 dB= − − − =

Now,

out inS S Gain

80 dBm 40dB

40 dBm

= +

= − += −

and

out inN N NF Gain

104 dBm 3 dB 40 dB

61 dBm

= + +

= − + += −

Hence, ( )outSNR 40 dBm 61 dBm 21 dB= − − − =

Question:In a two-stage amplifier, amplifier1 has a noisefigure of 3 dB and a gain of 20 dB. The secondamplifier has a noise figure of 6 dB. Find thetotal noise figure.

Answer:3.1 dB

Solution:First, express NF and gain as ratios

NF1 = 2

NF2 = 4Gain1 = 100

2total 1

1

total

NF 1NF NF

Gain

4 1NF 2

100

2.03

3.1 dB

−= +

−= +

==

Note that the noise figure of the

combination is hardly affected by thesecond amplifier.

Question:For the system previously discussed, NF1 = 1dB, NF2 = 6 dB, and G1 = 6 dB. What is thetotal noise figure?

Answer:3 dB

Solution::NF1 = 1.26, NF2 = 4.0, Gain = 4, so

2total 1

1

NF 1NF NFGain

4 11.26

4

2

3 dB

−= +

−= +

==

Because the gain of amplifier 1 is so low,the effect of the amplifier 2 is significant.


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Question:A parabolic dish antenna has a diameter of 1m. It operates at 10 GHz, where the free-spacewavelength is 0.03 m. Find the antenna’s gain,beamwidth and aperture.

Answer:

Gain = 38 dB ; Beamwidth = 1.8° ; Aperture =

0.5 m

2

Solution:

( )

( )

2 2

2

2 2

2

D 1Gain 6 6

λ 0.03

6670 38 dB

DBeamwidth 60 60 0.03

λ

1.8

πD π Aperture 0.6 0.6 1

4 4

0.5 m

= =

= =

= ° = °

= °

= =

=

Question:A parabolic dish antenna has a diameter of 3m, and operates at 4 GHz, where thewavelength is 0.075 m. Calculate the antennagain, beamwidth, and aperture.

Answer:

Gain = 40 dB ; Beamwidth = 1.5° ; Aperture =4.2 m2

Solution:2 2

2

2

D 3Gain 6 6λ 0.075

9600 40 dB

D 0.075Beamwidth 60 60

λ 3

1.5

π 9π Aperture 0.6 D 0.6

4 4

4.2 m

= =

= =

= ° = °

= °

= =

=

Question:Calculate the free-space path loss for anantenna operating at 6 GHz that is 25 mi fromthe transmitting antenna.

Answer:10-14

Solution:

( )

14

FSPL 97 20 log R 20 log F

97 20log(25 mi) 20log 6 GHz

140 dB

10−

= − − −

= − − −

= −

=

Question: The difference between incident (input) powerand transmitted power. It can be measured

and includes losses due to reflection andabsorption inside component.

Answer:Insertion loss

Question:Power lost inside component. It is equal toattenuation only if component is perfectlymatched.

Answer: Attenuation

Question:

An input signal is divided in a hybrid into twoequal outputs. What will be the phasedifference between the output signals of thefollowing hybrids are used?(a) 3-dB quadrature

hybrid, (b) 3-dB 180° hybrid, (c) Wilkinsoncombiner.

Answer:

(a) 90° ; (b)180° ; (c)0°

Question:A signal with an amplitude P1 is applied to oneof the input arms of a 3-dB quadrature hybrid.

A signal P2, which is 90° out of phase with P1, is

applied to the other input arm. What is thesignal on each of the output arms of the 3-dBquadrature hybrid?

Answer:P1 + P2 P1 – P2

Question:A circulator has an insertion loss of 1 dB and adirectivity of 21 dB. If a 0-dBm signal is putinto the input port and port 2 is shorted, howmuch power leaks back into the input port?

Answer:-22 dBm

Question:What type of filter can be electronically tuned?

Answer:YIG

Question: Three fixed attenuators with an insertion lossof 3, 6, and 10 dB are connected. What is thetotal insertion loss of the combination?


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Answer:19 dB

Question:What is the power level of the smallest signalthat can be detected above the noise by theSchottky diode?

Answer:-60 dB

Question:What is the power level of the largest signalthat will still be in the square-law range of aSchottky diode?

Answer:-20 dBm

Question:What is the purpose if an oscillator?

Answer:The purpose of an oscillator is to generate amicrowave signal.

Question: The variation in oscillator frequency caused bypower supply voltage or current changes

Answer:Frequency pushing

Question: The variation in oscillator frequency withchanges in load SWR

Answer:Frequency pulling

Question: The time it takes an electronically tunedoscillator to come within a specifiedpercentage of its final frequency after theelectronic control voltage has been changed.

Answer:Settling time

Question: The SNR at a receiver input is 30 dB. If thereceiver has a 5-dB noise figure, what is theSNR at the output?

Answer:

25 dB

Question:Name the three parts of a mixer

Answer:Local oscillator; combiner; Schottky diodes Question:

A mixer has a signal frequency of 10 GHz andan IF frequency of 10 MHz. What is the localoscillator frequency?

Answer:10.01 GHz or 9.99 GHz

Question:What is the advantage of a chip capacitorcompared with microstrip capacitor?

Answer: A chip capacitor provides much higher capacitance values

Question:What is the advantage of dielectric resonatorcompared with a microstrip resonator?

Answer: A dielectric resonator provides a much higher Q

Question:A very small (0.0007 in or 20 µ) wire used forconnecting components in a hybrid microwaveintegrated circuit.

Answer:Bond wire

Question:Provides greater capacitance than canobtained with microstrip capacitors

Answer:Overlay capacitor

Question:Connects from the top of the substrate to theground plane on the bottom

Answer:Via holeQuestion:What advantage do microwave tubes haveover microwave semiconductor devices?

Answer:Tubes can provide much greater power (over 10,000 times more power) than microwavesemiconductor devices.

Question:What is the major disadvantage of microwave

tubes? Answer:Their limited lifetime

Question:What is the advantage of using a low powersemiconductor oscillator driving a high powertube amplifier, instead of a high power tubeoscillator?

Answer:


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Frequency is much easier to control in thelower power semiconductor oscillator

Question:What is the major advantage of a griddedtube?

Answer:Low cost

Question:What is the major advantage of klystron?

Answer:High Power

Question:What is the major advantage of a helix TWT?

Answer:Wide bandwidth

Question:What is the major advantage of a coupled-cavity TWT?

Answer:Good bandwidth and high power achievedtogether

Question:What is the major advantage of a crossed-fieldamplifier?

Answer:High Efficiency

Question:What is the major disadvantage of a griddedtube?

Answer:

Gridded tubes work only at low frequency endof the microwave band

Question:What is the major disadvantage of a klystron?

Answer:Narrow bandwidthQuestion:What is the major disadvantage of TWTs?

Answer:Low efficiency

Question:

What are two disadvantage of a CFA? Answer:Low gain and high noise

Question:What limits the frequency capability of griddedtubes?

Answer:Transmit time of the electrons

Question:How do klystrons, TWTs, and CFAs avoid thetransmit time problem?

Answer:They use velocity modulation

Question:Forms the electron beam

Answer:Electron gun

Question:Focuses the electron beam through theklystron cavities

Answer:Focusing magnet

Question:Collects the electron beam after microwavepower has been extracted from it

Answer:Beam collector

Question:Modulates the microwave signal onto theelectron beam

Answer:Input Cavity

Question:Enhances the velocity modulation

Answer:Intermediate cavity

Question:Extracts microwave power from the bunched

electron beam Answer:Output cavity

Question:Collects the electron beam after microwavepower has been extracted from it

Answer:Beam collector

Question:Provides interaction between the microwavesignal and the electron beam in order to

generate microwave power Answer:Microwave interaction structure

Question:What type of magnetic focusing is mostcommonly used in a TWT?

Answer:Periodic permanent magnet (PPM) focusing


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Question:What is the advantage of a helix interactionstructure over a coupled cavity interactionstructure?

Answer:Wide Bandwidth

Question:What is the advantage of a coupled-cavityinteraction structure over a helix interactionstructure?

Answer:High Power

Question:What is the purpose of a depressed collector ina TWT?

Answer:To increase efficiency Question:What is the difference in function of themagnetic field in a TWT and in a CFA?

Answer:The magnetic field in a TWT is used only tofocus the electrons through the tube.The magnetic field in a CFA is part of thecrossed-field interaction process that allowshigh efficiency to be obtained.

Question:A separate electron gun is not used in anemitting-sole CFA, but the sole electrode whichprovides the crossed electric field, alsoprovides the electron beam.

Answer:

Emitting-sole CFA

Question:A magnetron is a high power oscillator tube.

Answer:Magnetron

Question:A microwave relay system that starts with thebaseband signal in the transmitter andmodulates this signal onto the microwavecarrier, receives the modulated microwavecarrier, and, after amplification, demodulates

the carrier to obtain the baseband signal at thereceiver.

Answer:Baseband microwave radio

Question:A technique for combining severaltransmitters, each operating in a differentfrequency channel, into a commontransmission line so that all the transmitters

can be connected to the same antenna. RFmultiplexing can be used in the same way toconnect several receivers to the samereceiving antenna?

Answer:RF multiplexingQuestion:A microwave relay repeater that receives themodulated microwave carrier and obtains thebaseband signal from it, and then remodulatesthe baseband signal onto another carrier andretransmits the new carrier with the basebandmodulated onto it.

Answer:Baseband repeater

Question:A microwave relay repeater that receives themodulated microwave carrier, amplifies it atthe IF frequency without removing thebaseband information and then up-convertsthe IF frequency to a new microwavefrequency for retransmission.

Answer:Heterodyne repeater

Question:A microwave relay repeater that amplifies thereceived microwave signal at the microwavefrequency and retransmits it withoutconverting the received signal to IF orbaseband frequencies.

Answer:RF amplifier

Question:

A repeater for digital signals that receives thenoisy digital bit stream and reconstructs it sothat a perfectly timed series of perfectlyshaped digital pulses is retransmitted

Answer:Regenerative repeater

Question: The ratio of the area of a one squarewavelength antenna to the area over which thetransmitted power has been spread (which is asphere with a radius equal to the transmitterreceiver separation)

Answer:Free-space path loss

Question: The reduction of the received signal in amicrowave relay due to the signal from amultipath being out-of-phase and canceling thedirect transmitted signal.

Answer:Multipath fading


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Question:A technique for reducing multipath fading bytransmitting the same information in twofrequency channels. This technique is based onthe fact that if a fade occurs at one frequencyit will not occur at the same instant of time ata different frequency.

Answer:Frequency diversity

Question:A technique for reducing multipath fading inwhich two receivers spaced approximately 100wavelengths apart, are used. This technique isbased on the fact that if a signal fades at oneantenna it will not fade at the same instant of time at the other antenna, since the pathlengths are different.

Answer:Space diversity

Question:A microwave relay system that achievestransmission distances beyond the curvatureof the earth by diffracting the microwavesignal off of hills and other obstacles in themicrowave path

Answer:Diffraction microwave relay system

Question:A microwave relay system that achievestransmission distances beyond the curvatureof the earth up to several hundred miles, byreceiving the microwave signal scattered fromair masses and clouds in the troposphere.

Answer:Troposcatter microwave relay system

Question:A transmission system used to send telephone,video, and data between buildings located a

few hundred feet to a few miles apart. Answer:Local area network

Question: Those microwave relay frequencies allocatedto long distance telephone companies for thetransmission of telephone, video and data forany customer.

Answer:

Common carrier frequency band

Question:A microwave relay that sends radio andtelevision program material from a distantlocation to the studio and from the studio tothe transmitter

Answer:Studio transmitter link

Question: The dividing of the common carrier or othermicrowave relay bands into channels. Separatetransmitters and receivers are used for eachchannel. The channel typically 20 MHz widecan handle 1000 telephone calls or onetelevision program.

Answer:Channelization of bandwidth

Question:A technique for transmitting differentinformation at the same frequency and in thesame direction from a microwave relaytransmitter to a receiver by using twopolarizations of the transmitted microwavefields.

Answer:Dual polarizationQuestion:Why is microwave relay often called aterrestrial microwave relay?

Answer:Because it is located on the surface of theearth.

Question:Why is microwave relay often called a line-of-sight relay?

Answer:Because the microwave signal travels inapproximately a straight line from thetransmitter to the receiver.

Question:What are the frequency ranges of the threemost commonly used common carrierfrequency bands?

Answer:

3.7 – 4.2 GHz; 5.925 – 6.425 GHz; 10.7 – 11.7GHz

Question:What is the frequency range of the mostcommon industrial relay band?

Answer:6.575 – 6.875 GHz

Question:


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What two frequency bands are most oftenused for local area microwave networks?

Answer:18.58 – 19.16 GHz; 21.2 – 23.6 GHz

Question:What are the typical transmitter-receiverspacings for microwave relay?

Answer:10 – 50 mi

Question:What limits the transmitter-receiver spacingfor a microwave relay?

Answer:The curvature of the earth

Question:An antenna covering that the transmitted orreceived microwave power can pass throughused to protect the antenna and the antennafeed from weather.

Answer:Radome

Question:A microwave relay antenna consisting of ahorn that radiates onto a reflector. It is madeas a single unit and has lower sidelobes than aparabolic dish antenna.

Answer:Horn-reflector antenna

Question:What carrier-to-noise ratio is required formicrowave relay systems?

Answer:10-20 dB

Summary on Antenna

Question: The amount by which an antenna concentratesits radiation in a given direction relative towhat would have been obtained if the antennahad not been used

Answer:Gain

Question: The effective area of the antenna for receivingmicrowave power

Answer:

Receiving area

Question: The angular width of the antenna beambetween the points on either side of the axiswhere the transmitted power has beenreduced by one-half

Answer:Beamwidth

Question: The direction of the electric field in theelectromagnetic wave radiated from anantenna. May be horizontal, vertical or circular

Answer:Polarization

Question: The frequency range over which an antennahas the required gain, area, or othercharacteristics.

Answer:Bandwidth

Question:Radiation from an antenna at other anglesthan the desired direction

Answer:Sidelobes

Question:A measure of the microwave power radiatesfrom an antenna as a function of angulardirection from the antenna axis

Answer: Antenna pattern

Question:A hypothetical antenna radiating or receivingequally well in all directions

Answer:Isotropic antenna

Question:What is the gain of an isotropic antenna?

Answer:0 dB

Question:What is the purpose of a phased array radar?

Answer:To move the antenna beam without movingthe antenna

Question:How far apart must the antenna elements of aphased array radar be placed?

Answer:


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½ wavelength

Question: The total transmitted power is radiated from afeed horn onto the array surface. The phase isshifted at each element of the array andreflected to form the beam

Answer:Reflected array

Question: The total transmitted power is radiated from afeed horn onto the array surface. The phase isshifted at each element of the array andtransmitted out the other side.

Answer:Lens array

Summary on Principles onCommunications

Question: The electrical signal to be transmitted. Thiselectrical signal may represent audio, video ordigital data

Answer:Baseband

Question: The electrical signal used to carry thebaseband information from one location toanother.

Answer:

Carrier

Question:Variation of the carrier amplitude, frequency,or phase by the baseband signal, so that thebaseband signal can be transmitted via thecarrier.

Answer:Modulation

Question:Removal of the baseband information from thecarrier at the receiving end, so that the

baseband signal can be used. Answer:Demodulation

Question:Modulation of the baseband onto the carrier byvarying the frequency

Answer:

Frequency Modulation (FM)

Question:Modulation of the baseband signal onto thecarrier by varying the amplitude

Answer: Amplitude Modulation (AM)

Question:Frequencies present in the amplitudemodulated or frequency modulated carrier dueto the modulation process.

Answer:Sidebands

Question: The frequency range over which themodulation sidebands exist.

Answer:Bandwidth

Question:An amplitude modulation process where thecarrier and one set of modulation sidebandsare removed to reduce bandwidthrequirements

Answer:Single-Sideband (SSB)

Question:A method of combining several signals, all of which occupy the same frequency range, into abaseband so that they do not interfere eachother.

Answer:Multiplexing

Question:A multiplexing technique where each signal tobe multiplexed is shifted from its originalfrequency and then combined.

Answer:Frequency-division Multiplexing (FDM)

Question: The baseband signal is sampled in time, andeach sample is represented by a digital code.

Answer:Pulse Code Modulation (PCM)

Question:A multiplexing method where several signalsare combined by forming PCM codes of eachand then interleaving the PCM pulses.

Answer:Time-division multiplexing (TDM)


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Question: The ratio of the received microwave carrier tothe microwave noise in the receiver

Answer:Carrier-to-noise ratio (C/N)

Question: The ratio of the received signal to noise afterthe signal has been demodulated to get outthe baseband information.

Answer:Signal-to-noise ratio (S / N)

Question: The frequency range of a single telephonesignal is from _____ Hz to ____ Hz.

Answer:300 – 3400 Hz

Question:A single telephone signal is fitted into afrequency band from ___ Hz to ____ Hz.

Answer:0 – 4000 Hz

Question:How many telephone signals are frequency-division-multiplexed together to form an FDMgroup?

Answer:12

Question:What is the frequency range of an FDM basicgroup?

Answer:60 - 108 kHz

Question: The frequency range of a single TV signal from ____ to ___ MHz Answer:0 – 4 Mhz

Question:How many digital bits are required for a singleletter in an asynchronous ASCII code withparity?

Answer:10

Question:What signal-to-noise ratio is required forsatisfactory telephone service?

Answer:50 dB

Question:

What signal-to-noise ratio is required forsatisfactory telephone reception?

Answer:40 dB

Question:Coding of an analog signal into a series of digital pulses is called _____.

Answer:Pulse code modulation (PCM)

Question: The combining of many telephone signalstogether by first coding each into a series of digital pulses and then interleaving the pulsesseries of each signal is called ______.

Answer:Time-division multiplexing (TDM)

Question:What must be the PCM sampling rate on a 4-kHz analog signal?

Answer:8 kHz

Question:What is the quantization signal-to-noise ratio if an eight-digit PCM code is used?

Answer:50 dB

Question:What is the digital bit rate for a standard PCMtelephone channel?

Answer:64 kb/s

Question: The changing of digital signals from acomputer into frequency tones fortransmission down a conventional voice gradetelephone circuit is done in a _____.

Answer:Modem

Question:What is the advantage of FM compared withAM?

Answer:

Signal-to-noise improvement

Question:What is the advantage of FM compared withFM?

Answer:Less transmission bandwidth required


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Summary on SatelliteCommunications

Question:A satellite communication system designed forcommunication from one continent to another.

Answer:

International satellite

Question:A satellite communication system designed forcommunicating within a given continent orgeographical area, such as the United States.

Answer:Domestic satellite

Question:A satellite system designed for ship-to-shorecommunication.

Answer:MARISAT

Question:A satellite communication system designed tobroadcast television directly from the satelliteat a home TV receiver.

Answer:Direct broadcast satellite

Question: The orbit of satellites around the earth’sequator in which the satellite takes 24 h to

completely orbit the earth, so that the satelliteappears in a stationary location relative to therotating earth.

Answer:Synchronous orbit

Question:It is the effective radiated power of thesatellite transmitter. It is equal to the productof the transmitter power times the transmitterantenna gain, and this single quantitycompletely characterizes the satellitetransmitter.

Answer:ERP

Question:Completely characterizes the earth stationreceiver of a satellite communication system,and is equal to the ratio of the receiverantenna gain to the total noise temperature of the receiver (including the antenna noise

temperature plus the receiver amplifier noisetemperature).

Answer:G/T

Question:A satellite that maintains its orientation inspace relative to the earth by spinning aboutits axis at a rate of about 50 revolutions perminute

Answer:Spin-stabilized satellite

Question:A satellite that maintains a fixed orientation inspace relative to the earth by continuallycorrecting its orientation by firing small jets

Answer:Three-axis stabilized satellite

Question:A single channel of the communication systemEach transponder in a satellite has its ownseparate transmitter. It is typically 40 MHzwide

Answer:Transponder

Question:Received power contours from satellite on theearth’s surface. The satellite antenna isdesigned, often with multiple feed horns, to

direct its power onto particular geographicareas, and this pattern of received power onthe earth’s surface is the antenna footprint.

Answer: Antenna footprint

Question:An antenna beam from the satellite that coversthe entire one third of the earth’s surface thatcan be seen from the satellite

Answer:Global beam

Question: The antenna beam from the satellite thatcovers a limited geographic region, such aspart of a country, an entire country, acontinent, or a hemisphere. Some satelliteshave a variety of spot beams, each covering alarger or smaller geographic area.

Answer:Spot beam


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Question:What is the synchronous orbit for acommunication satellite in miles?

Answer:22,300 mi

Summary on RADAR

Communications

Question:A radar that measures the distance betweenthe radar and a target by determining the timerequired for a microwave signal to travel fromthe radar to the target and back.

Answer:Range-measuring radar

Question:A radar that measures the velocity of a target

by determining the change in the frequency of the reflected microwave signal due to thetarget’s velocity. This change in frequency iscalled the Doppler’s shift, and so this type of radar is often called a Doppler radar.

Answer:Velocity-measuring radar

Question:A radar that measures both the distance to a

target and its velocity by measuring both thechange in frequency of the reflected signal andtime required for the microwave signal totravel from the transmitter to the target andback to the radar.

Answer:Pulse Doppler radar

Question:A radar that measures the range to the targetand distinguishes between moving andstationary targets.

Answer:

Moving-target-indicator (MTI) radar

Question:A radar that obtains high range resolution byvarying the frequency of the transmittedmicrowave signal and then compresses thepulse in the receiver.

Answer:Pulse-compression radar

Question:A radar that scans its beam over a givenvolume of space to determine if targets arepresent.

Answer:Search radar

Question:A radar that directs its beam into a given areaof space to determine accurately the angularlocation of a target.

Answer:Tracking radar

Question:A tracking radar that determines the angularlocation of a target with a single pulse.

Answer:Monopulse radar

Question:A radar that moves its beam through space bychanging the phase of a multiplicity of transmitting elements that make up theantenna rather than mechanically moving theentire antenna.

Answer:Phased array radar

Question:A radar using a single antenna element, whichobtains extremely high angular resolution bymoving this single element over a longdistance, storing the information obtained fromthe antenna at each position, and thenrecombining the received information.

Answer:Synthetic Aperture radar

Question:What three things can a radar measure?

Answer:Range; velocity; angle (azimuth and elevation)

Question:Which of the following can radar measure withthe best accuracy?

Answer:Velocity

Question:Which of the above are the most difficult for aradar to measure accurately?

Answer: Angle

Summary on RADAR Warfare


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Question:A radar has a transmitter power of 10 kW, anarea of 10 m2, a gain of 40 dB, and the rangebetween the radar and the target is 100 km.

The target cross section is 100 m2, the totalatmospheric and system losses are 4 dB,(2.5times) the receiver noise figure is 2 dB, andthe bandwidth is 1 MHz.

Answer:26 dBSolution:

( )

( ) ( ) ( ) ( )

( ) ( ) ( )

R 2 4

4 4 2 2 2

42 5

R

PGσAP

4π R L

10 W 10 10 m 10 m

4π 10 m 2.5

2.5 pW

86 dBm

N 114 2 2.5 112

P 26 dBN

=

=

=

= −

= − + + = −

∴ =

Question: The techniques, equipment, and tactics usedto render electronic target location andelectronic weapons control ineffective.

Answer:Electronic Warfare (EW)

Question: The techniques and equipment used to render

electronic target location and weapon controlineffective. It include tactics such as flightplans to avoid detection, electronicsurveillance, spying techniques to determinehow enemy weapon systems work and theirdeployment, and the jamming of infrared,optical, and radar target location and controlsystems.

Answer:Electronic Welfare

Question: The electronic techniques and equipment usedto render electronic target location andelectronic weapons control ineffective.

Answer:Electronic Countermeasures (ECM)

Question:

It is sometimes used interchangeably with theterm electronic warfare. In the strict sense,electronic countermeasures applies only totechniques and equipment used to renderelectronic target location and weapon controlsystems ineffective.

Answer:Electronic countermeasure

Question: These are the techniques an equipment usedby the radar to reduce the effectiveness of theenemy’s jamming against it.

Answer:Electronic counter-countermeasures (ECCM)

Question: Techniques and equipment used by the radarto render ECM ineffective.

Answer:Electronic Counter-Countermeasures (ECCM)

Question:Are the equipment used to determine theelectronic characteristics of the enemy targetlocation and weapon control systems, and todetermine what should be jammed by theelectronic countermeasures.

Answer:Electronic support measures (ESM)

Question: The equipment used to determine thecharacteristics of the enemy’s electronic targetlocation and electronic weapons controlsystem.

Answer:Electronic Support Measures (ESM)

Question:Aircraft are specially designed to reduce theamount of microwave power they reflect sothat they cannot be seen by radar.

Answer:Stealth

Question:It is an electronic countermeasure technique inwhich the aircraft is completely redesigned to

greatly reduce its radar cross section. Answer:Stealth

Question:A missile is launched by the target to home onthe microwave signal transmitted by the radar


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This forces the radar to shut down or bedestroyed.

Answer: Anti-radiation missile

Question:An anti-radiation missile uses the radartransmissions as a beacon and homes on theradar to destroy it.

Answer: Anti-radiation missile (ARM)

Question:A metal foil dropped from an aircraft orlaunched from a ship or land vehicle thatreflects a microwave signal back to the radarto create false targets.

Answer:Chaff

Question:Is a metal foil launched from a target to createfalse radar target

Answer:Chaff

Question:Is another name for barrage jamming, andstresses that the barrage jamming sourcemust be out of the range of enemy missiles sothat they cannot home on the jamming.

Answer:Stand-off jamming

Question:Is the repeating back of an amplified version of

the radar signal with its characteristicschanged to give false information to the radar.

Answer:Deceptive jamming

Question: The jammer repeats an amplified version of the radar signal, but with false information.

The radar determines the range, velocity, andangular location of the target with this falseinformation.

Answer:Deceptive Jamming

Question:Are small missiles with amplifiers in them.

They receive and amplify the radar signal andtransmit it back to the radar, so that they looklike targets.

Answer:Decoys

Question:

Is a small unarmed missile launched fromaircraft, or a buoy launched from ships, tocreate false radar targets

Answer:Decoy

Question:Noise-modulated microwave signals aretransmitted to raise the noise level in the radarreceiver so that the radar cannot accuratelydetermine the range, velocity, or angularlocation of the target. The technique isdangerous because the enemy can launchmissiles that home on the jamming signal.

Answer:Noise Jamming

Question:A deceptive jamming technique where thereceived radar signal is amplified and sentback to the radar delayed in time from theactual reflected radar signal so that the radarthinks the target is further away that is reallyis.

Answer:Range-gate pull-off (RGPO)

Question:A deceptive jamming technique where the

jamming pulse is sent to the radar before theactual echo from the target so that the radarthinks that the target is closer to the radar thatit really is.

Answer:Range-gate pull-in (RGPI)

Question:A deceptive jamming technique where the

jamming signal is given a false Doppler shift sothat the radar thinks the target velocity isdifferent than it really is.

Answer:Velocity-gate pull-off (VGPO)

Question:A deceptive jamming technique where theradar is transmitted with an amplitudevariation that is out of phase with the conical

scan information so that the radar thinks thatthe target is a different angular location.

Answer:Inverse conical-scan jamming

Question:Is the transmission of noise-modulated highpower microwave power microwave signals toraise the noise level in the enemy radar


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receiver so that range and velocity informationcannot be obtained.

Answer:Barrage jamming

Question:A ECCM technique where the radar launches amissile to home on the barrage jamming ordeceptive jamming signal. The jammer thenserves as a beacon to guide the attackingmissile to it.

Answer:Home-on jammer

Question:An ESM receiver consisting of many mixer-localoscillator-IF amplifiers in parallel toinstantaneously determine the frequency of the radar signals.

Answer:Channelized receiver

Question:An ESM receiver using optoacoustical effects toinstantly determine the time of arrival and thefrequency of the radar signals

Answer:Bragg Cell

Summary on Microwave

CommunicationsQuestion:What is the microwave transmission frequencyof GPS satellites?

Answer:1.575 GHz

Question:What is the frequency range of cellulartelephones?

Answer:806 – 949 MHz

Question:What is the frequency of microwave ovens?

Answer:2.450 GHz

Question:Operating frequency for UHF TV

Answer: 600 MHz

Question:Operating frequency for microwave relay

Answer: 3.9 GHz

Question:Operating frequency for satellitecommunication

Answer: 6 GHz (up)4 GHz (down)

Question:Operating frequency for troposcattercommunication

Answer: 2 GHz

Question:Operating frequency for mobile radio

Answer: 900 MHz

Question:Operating frequency for telemetry

Answer: 2 GHz

Question:What two problems prevent conventionalelectronic equipment from working atmicrowave frequencies?

Answer: Lead Reactance and Transmit Time

Question:What are the three types of microwavetransmission lines?

Answer: Coaxial cable; stripline; waveguide

Question:Determine the guide wavelength at 3 GHz for a50-Ω stripline using 0.03-in.-thick Teflon

fiberglass (ε = 2.55). Answer:6.26 cm

Solution::


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( ) ( )

0

0g

Zε 50 2 .55 79 .8 Ω

w0.75

b

w 0.75 2 x 0.03 0.045 in.

Then,

λλ

ε

10 cm

2.556.26 cm

= =

=

= =

=

=

=

Summary on Latest ECE Laws

Question:An executive order which gave NTC a vestedpower to promulgate rules and regulations, aspublic safety interest may require, toencourage as larger and more effective use of communications, radio and televisionbroadcasting facilities, and to maintain

effective competition. Answer:E.O. 546

Question: The maximum frequency separationrequirement for FM broadcast stations.

Answer:800 kHz

Question: The maximum number of low power FM radiobroadcast stations be allowed for any

geographical region. Answer:30

Question: The maximum number of low power FM radiobroadcast stations may be operated/allowed tobe established nationwide.

Answer:200

Question:All classes of FM stations shall be protected up

to protected up to _____ or _____. Answer:1 mV/m or 60 dBu contour

Question:NTC memorandum circular on the guidelinesfor the grant and authorization of 500 watts FMbroadcast stations.

Answer:M.C. 02-06-2006

Question:Consider as low power FM Broadcast Station.

Answer:500 W. FM Broadcast stations

Question:Authorized transmitted power output for classB-1 FM station.

Answer:500 W

Question:Class B-1 FM station

Answer:ERP: not lower 1 kW and not exceeding 5 kW

Antenna height: limited to 200 feet aboveaverage terrain

Question:Class B Station

Answer: Authorized power transmitter power of not exceeding 10 kW ERP: not exceeding 30 kW

Antenna Height: limited to 500 feet aboveaverage terrainMinimum TXR Power: 1 kW

Question:National Telecommunication CommissionMemorandum Circular which pertains toprogram standards for radio and TV Broadcastand Cable TV stations.

Answer:M.C. 1-3-2006

Question:A Memorandum Circular issued by NTC inrelation to the “use and operation of radiofrequency identification (RFID)”.

Answer:M.C. 03-08-2006

Question: The RFID frequency range Answer:13.553 – 13.567 MHz 918 – 920 MHz 2446 – 2454 MHz

Question: These are intended to carry data in suitabletransponders, generally known as tags, and to


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retrieve data, by hand-or-machine-readablemeans, at a suitable time and place to satisfyparticular application needs.

Answer:Radio Frequency Identification System

Question:It employs time chips and wireless antennasthat can be embedded into products and usedfor unique identification purposes.

Answer:RFID

Question:A device which transmits aninterrogating/querying signal to an RFID tagand receives unique information from the tag

Answer:Proximity readers

Question:Classification of proximity reader with erp notexceeding 500 mW.

Answer:Low power

Question:Class of Proximity with erp not exceeding 2watts (or 4 watts eirp)

Answer:High power

Question:A microchip attached to an antenna that picksup signals from and sends signals to a reader

Answer:

RFID tag

Question:Class of RFID used for long distance purposessuch as in toll highways, parking areas, andgas stations.

Answer: Active tag

Question:Class of RFID used for near and in closeproximity to a reader and does not use anyinternal battery.

Answer:Passive tags

Question: The Electronics Engineering Law of 2004 Answer: R.A. 9292

Question:Date signed into Law by President GloriaArroyo.

Answer: April 17, 2004

Question:Date the R.A. 9292 published at Manila Times

Answer: May 12, 2004

Question:Date the Electronics Engineering Law of 2004takes effective

Answer: May 27, 2004

Question:Penalty for operating Radio FrequencyIdentification (RFID) proximity reader withoutvalid registration

Answer: P5,000 per reader

Question:Penalty for selling unregistered RFID proximityreader

Answer:P5,000 per unit or with forfeiture of equipment

Question:Penalty for selling of RFID proximity readers bynon-NTC accredited radiodealers/manufacturers

Answer:P5,000 per reader, P1,000 per 1000 tags

Question:Registration fee for low power readers

Answer:P100

Question:Registration fee for high power readers

Answer:P300

Question:A low power RFID readers has an ERP of _____.

Answer:Not exceeding 500 mW

Question: A high power RFID readers has an ERP of ____. Answer:Not exceeding 2 watts (or 4 watts EIRP)


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Question:FM Broadcast Stations which are allowed tooperate in Established Service Areas

Answer:Class A or Class B FM Broadcast Stations

Question:FM Broadcast Stations which are allowed tooperate in areas outside of the EstablishmentService Area

Answer:Class B-1

Question:Broadcast/Push messaging services shall notbe sent between _____ except on paidsubscription services based on NTCrecommendation.

Answer:9:00 pm – 7:00 am

Question:Penalty for violating rules and regulations onBroadcast Messaging Services set by NTC

Answer:P200 fine per violation

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