Electronics interview questions on Communication SystemSample interview questions for ECE branch: (Communication Systems)

Expand ECE.

Electronics & Communication Engineering.

What is Electronic?

The study and use of electrical devices that operate by controlling the flow of electrons or other

electrically charged particles.

What is communication?

Communication means transferring a signal from the transmitter which passes through a medium then

the output is obtained at the receiver. (or)communication says as transferring of message from one

place to another place called communication.

Different types of communications? Explain.

Analog and digital communication.

As a technology, analog is the process of taking an audio or video signal (the human voice) and

translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format

where the audio or video data is represented by a series of "1"s and "0"s.

Digital signals are immune to noise, quality of transmission and reception is good, components used in

digital communication can be produced with high precision and power consumption is also very less

when compared with analog signals.

What is engineering?

The application of science to the needs of humanity and a profession in which a knowledge of the

mathematical and natural sciences gained by study, experience, and practice is applied with judgment to

develop ways to use economically the materials and forces of nature for the benefit of mankind.

Difference between electronic and electrical.

Electronics work on DC and with a voltage range of -48vDC to +48vDC. If the electronic device is plugged

into a standard wall outlet, there will be a transformer inside which will convert the AC voltage you are

supplying to the required DC voltage needed by the device. Examples: Computer, radio, T.V, etc...

Electric devices use line voltage (120vAC, 240vAC, etc...). Electric devices can also be designed to operate

on DC sources, but will be at DC voltages above 48v. Examples: are incandescent lights, heaters, fridge,

stove, etc...

What is sampling?

The process of obtaining a set of samples from a continuous function of time x(t) is referred to as

sampling.

State sampling theorem.

It states that, while taking the samples of a continuous signal, it has to be taken care that the sampling

rate is equal to or greater than twice the cut off frequency and the minimum sampling rate is known as

the Nyquist rate.

What is cut-off frequency?

The frequency at which the response is -3dB with respect to the maximum response.

What is pass band?

Passband is the range of frequencies or wavelengths that can pass through a filter without being

attenuated.

What is stop band?

A stopband is a band of frequencies, between specified limits, in which a circuit, such as a filter or

telephone circuit, does not let signals through, or the attenuation is above the required stopband

attenuation level.

Difference between mobile and a cell phone.

There is no difference, just language use, which differs from country to country, so in Britain it is called a

mobile, and in USA and South Africa and other places a cell phone.

Even in Europe the name differs. The Germans call it a "handy", which in English has completely another

meaning as an adjective, meaning useful.

In Italy it is called a telofonino or "little phone".

This difference in British and American English is also evident in many other things we use every day,

like lifts and elevators, nappies and diapers, pickups and trucks. The list goes on and on, any student of

English has to decide which he or she will use, as the default setting.

Explain RF?

Radio frequency (RF) is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This

range corresponds to frequency of alternating current electrical signals used to produce and detect

radio waves. Since most of this range is beyond the vibration rate that most mechanical systems can

respond to, RF usually refers to oscillations in electrical circuits or electromagnetic radiation.

What is modulation? And where it is utilized?

Modulation is the process of varying some characteristic of a periodic wave with an external signals.

Radio communication superimposes this information bearing signal onto a carrier signal.

These high frequency carrier signals can be transmitted over the air easily and are capable of travelling

long distances.

The characteristics (amplitude, frequency, or phase) of the carrier signal are varied in accordance with

the information bearing signal.

Modulation is utilized to send an information bearing signal over long distances.

What is demodulation?

Demodulation is the act of removing the modulation from an analog signal to get the original baseband

signal back. Demodulating is necessary because the receiver system receives a modulated signal with

specific characteristics and it needs to turn it to base-band.

Name the modulation techniques.

For Analog modulation--AM, SSB, FM, PM and SM

Digital modulation--OOK, FSK, ASK, Psk, QAM, MSK, CPM, PPM, TCM, OFDM

Explain AM and FM.

AM-Amplitude modulation is a type of modulation where the amplitude of the carrier signal is varied in

accordance with the information bearing signal.

FM-Frequency modulation is a type of modulation where the frequency of the carrier signal is varied in

accordance with the information bearing signal.

where do we use AM and FM?

AM is used for video signals for example TV. Ranges from 535 to 1705 kHz.

FM is used for audio signals for example Radio. Ranges from 88 to 108 MHz.

How does a mobile work?

When you talk into a mobile telephone it converts the sound of your voice to radiofrequency energy

(radio waves). The radio waves are transmitted through the air to a nearby base station. The base

station then sends the call through the telephone network until it reaches the person you are calling.

When you receive a call on your mobile phone the message travels through the telephone network until

it reaches a base station near to you. The base station sends out radio waves, which are detected by your

telephone and converted back to speech. Depending on the equipment and the operator, the frequency

that each operator utilises is 900MHz, 1800MHz or 2100MHz.

The mobile phone network operates on the basis of a series of cells. Each cell requires a radio base

station to enable it to function.

There are three types of base station and each has a particular purpose:

The Macrocell is the largest type and provides the main coverage for mobile phone networks.

The Microcell is used to improve capacity in areas where demand to make calls is high, such as shopping

centres.

The Picocell only has a range of a few hundred metres and may be used to boost weak signals within

large buildings.

Each base station can only cope with a certain number of calls at any one time. So if demand exceeds the

capacity of a base station an additional base station is needed.

What is a base station?

Base station is a radio receiver/transmitter that serves as the hub of the local wireless network, and may

also be the gateway between a wired network and the wireless network.

How many satellites are required to cover the earth?

3 satellites are required to cover the entire earth, which is placed at 120 degree to each other. The life

span of the satellite is about 15 years.

What is a repeater?

A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher

power, or onto the other side of an obstruction, so that the signal can cover longer distances without

degradation.

What is attenuation?

Attenuation is the reduction in amplitude and intensity of a signal. Signals may attenuate exponentially

by transmission through a medium, or by increments calculated in electronic circuitry or set by variable

controls. Attenuation is an important property in telecommunications and ultrasound applications

because of its importance in determining signal strength as a function of distance. Attenuation is usually

measured in units of decibels per unit length of medium (dB/cm, dB/km, etc) and is represented by the

attenuation coefficient of the medium in question.

What is multiplexing?

Multiplexing (known as muxing) is a term used to refer to a processwhere multiple analog message

signals or digital data streams are combined into one signal over a shared medium. The aim is to share

an expensive resource. For example, in telecommunications, several phone calls may be transferred

using one wire.

What is CDMA, TDMA, FDMA?

Code division multiple access (CDMA) is a channel access methodutilized by various radio

communication technologies. CDMA employsspread-spectrum technology and a special coding scheme

(where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same

physical channel. By contrast, time division multiple access (TDMA) divides access by time,

whilefrequency-division multiple access (FDMA) divides it byfrequency.

An analogy to the problem of multiple access is a room (channel) in which people wish to communicate

with each other. To avoid confusion, people could take turns speaking (time division), speak at different

pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would

speak different languages. People speaking the same language can understand each other, but not other

people. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the

same channel, but only users associated with a particular code can understand each other.

Difference between CDMA and GSM.

These are the two different means of mobile communication being presently used worldwide. The basic

difference lies in the Multiplexing method used in the aerial communication i.e. from Mobile Tower to

your mobile and vice versa.

CDMA uses Code Division Multiple Access as the name itself indicates, for example you are in a hall

occupied with number of people speaking different language. You will find that the one language you

know will be heard by you and the others will be treated like noise. In the same manner each CDMA

mobile communication takes place with a "code" communicating between them and the other end if one

is knowing that code then only it can listen to the data being transmitted i.e. the communication is in the

coded form.

On the other hand GSM (Global System for Mobile Communications)uses narrowband TDMA, which

allows eight simultaneous calls on the same radio frequency. TDMA works by dividing a radio frequency

into time slots and then allocating slots to multiple calls. In this way, a single frequency can support

multiple, simultaneous data channels.

What is an Amplifier?

An electronic device or electrical circuit that is used to boost (amplify) the power, voltage or current of

an applied signal.

What is Barkhausen criteria?

Barkhausen criteria, without which you will not know which conditions, are to be satisfied for

oscillations.

“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product of the

transfer gain of the amplifier and the magnitude of the feedback factor of the feedback network ( the

magnitude of the loop gain ) are less than unity”.

The condition of unity loop gain -A = 1 is called theβ  Barkhausencriterion. This condition implies that

| A |= 1and that the phase of - Aβ β is zero.

Explain Full duplex and half duplex.

Full duplex refers to the transmission of data in two directions simultaneously. For example, a

telephone is a full-duplex devicebecause both parties can talk at once. In contrast, a walkie-talkie is

ahalf-duplex device because only one party can transmit at a time.

Most modems have a switch that lets you choose between full-duplex and half-duplex modes. The

choice depends on whichcommunications program you are running.

In full-duplex mode, data you transmit does not appear on yourscreen until it has been received and

sent back by the other party. This enables you to validate that the data has been accurately transmitted.

If your display screen shows two of each character, it probably means that your modem is set to half-

duplex mode when it should be in full-duplex mode.

What is a feedback? And explain different types of feedback.

Feedback is a process whereby some proportion of the output signal of a system is passed (fed back) to

the input. This is often used to control the dynamic behaviour of the system.

Types of feedback:

Negative feedback: This tends to reduce output (but in amplifiers, stabilizes and linearizes

operation). Negative feedback feeds part of a system's output, inverted, into the system's input;

generally with the result that fluctuations are attenuated.

Positive feedback: This tends to increase output. Positive feedback, sometimes referred to as

"cumulative causation", is a feedback loop system in which the system responds

to perturbation (Aperturbation means a system, is an alteration of function, induced by external or

internal mechanisms) in the same direction as the perturbation. In contrast, a system that responds to

the perturbation in the opposite direction is called a negative feedback system.

Bipolar feedback: which can either increase or decrease output.

Advantages of negative feedback over positive feedback.

Much attention has been given by researchers to negative feedback processes, because negative

feedback processes lead systems towards equilibrium states. Positive feedback reinforces a given

tendency of a system and can lead a system away from equilibrium states, possibly causing quite

unexpected results.

Example for negative feedback and positive feedback.

Example for –ve feedback is ---Amplifiers

And for +ve feedback is – Oscillators

What is Oscillator?

An oscillator is a circuit that creates a waveform output from a direct current input. The two main types

of oscillator are harmonic and relaxation. The harmonic oscillators have smooth curved waveforms,

while relaxation oscillators have waveforms with sharp changes.

What is a transducer and transponder?

A transducer is a device, usually electrical, electronic, electro-

mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical

attribute to another for various purposes including measurement or information transfer.

In telecommunication, the term transponder (short-forTransmitter-responder and sometimes

abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:

An automatic device that receives, amplifies, andretransmits a signal on a different frequency (see

alsobroadcast translator).

An automatic device that transmits a predetermined messagein response to a predefined received

signal.

A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.

A communications satellite’s channels are called transponders, because each is a

separate transceiver or repeater.

What is an Integrated Circuit?

An integrated circuit (IC), also called a microchip, is an electronic circuit etched onto a silicon chip. Their

main advantages are low cost, low power, high performance, and very small size.

What is crosstalk?

Crosstalk is a form of interference caused by signals in nearby conductors. The most common example is

hearing an unwanted conversation on the telephone. Crosstalk can also occur in radios, televisions,

networking equipment, and even electric guitars.

What is a rectifier?

A rectifier changes alternating current into direct current. This process is called rectification. The three

main types of rectifier are the half-wave, full-wave, and bridge. A rectifier is the opposite of an inverter,

which changes direct current into alternating current.

HWR- The simplest type is the half-wave rectifier, which can be made with just one diode. When the

voltage of the alternating current is positive, the diode becomes forward-biased and current flows

through it. When the voltage is negative, the diode is reverse-biased and the current stops. The result is

a clipped copy of the alternating current waveform with only positive voltage, and an average voltage

that is one third of the peak input voltage. This pulsating direct current is adequate for some

components, but others require a more steady current. This requires a full-wave rectifier that can

convert both parts of the cycle to positive voltage.

FWR- The full-wave rectifier is essentially two half-wave rectifiers, and can be made with two diodes

and an earthed centre tap on the transformer. The positive voltage half of the cycle flows through one

diode, and the negative half flows through the other. The centre tap allows the circuit to be completed

because current cannot flow through the other diode. The result is still a pulsating direct current but

with just over half the input peak voltage, and double the frequency.

What is resistor?

A resistor is a two-terminal electronic component that opposes anelectric current by producing a

voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's

law: V= IR.

What is capacitor?

A capacitor is an electrical/electronic device that can store energyin the electric field between a pair

of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging",

and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.

Capacitors are often used in electric and electronic circuits asenergy-storage devices. They can also be

used to differentiate between high-frequency and low-frequency signals. This property makes them

useful in electronic filters.

Capacitors are occasionally referred to as condensers. This term is considered archaic in English, but

most other languages use acognate of condenser to refer to a capacitor.

What is inductor?

An inductor is a passive electrical device employed in electrical circuits for its property of inductance.

An inductor can take many forms.

What is conductor?

A substance, body, or device that readily conducts heat, electricity, sound, etc. Copper is a good

conductor of electricity.

What is a semi conductor?

A semiconductor is a solid material that has electrical conductivityin between that of a conductor and

that of an insulator(AnInsulator is a material that resists the flow of electric current. It is an object

intended to support or separate electrical conductorswithout passing current through itself); it can

vary over that wide range either permanently or dynamically.

What is diode?

In electronics, a diode is a two-terminal device. Diodes have two active electrodes between which the

signal of interest may flow, and most are used for their unidirectional current property.

What is transistor?

In electronics, a transistor is a semiconductor device commonly used to amplify or

switch electronic signals. The transistor is the fundamental building block of computers, and all other

modernelectronic devices. Some transistors are packaged individually but most are found

in integrated circuits.

What is op-amp?

An operational amplifier, often called an op-amp , is a DC-coupledhigh-gain electronic

voltage amplifier with differential inputs[1] and, usually, a single output. Typically the output of the op-

amp is controlled either by negative feedback, which largely determines the magnitude of its output

voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation

50 Common Interview Questions and Answers

Review these typical interview questions and think about how you would answer them. Read

the questions listed; you will also find some strategy suggestions with it.

1. Tell me about yourself:

The most often asked question in interviews. You need to have a short statement prepared in your

mind. Be careful that it does not sound rehearsed. Limit it to work-related items unless instructed

otherwise. Talk about things you have done and jobs you have held that relate to the position you

are interviewing for. Start with the item farthest back and work up to the present.

2. Why did you leave your last job?

Stay positive regardless of the circumstances. Never refer to a major problem with management and

never speak ill of supervisors, co- workers or the organization. If you do, you will be the one looking

bad. Keep smiling and talk about leaving for a positive reason such as an opportunity, a chance to

do something special or other forward- looking reasons.

3. What experience do you have in this field?

Speak about specifics that relate to the position you are applying for. If you do not have specific

experience, get as close as you can.

4. Do you consider yourself successful?

You should always answer yes and briefly explain why. A good explanation is that you have set

goals, and you have met some and are on track to achieve the others.5. What do co-workers say

about you?

Be prepared with a quote or two from co-workers. Either a specific statement or a paraphrase will

work. Jill Clark, a co-worker at Smith Company, always said I was the hardest workers she had ever

known. It is as powerful as Jill having said it at the interview herself.

6. What do you know about this organization?

This question is one reason to do some research on the organization before the interview. Find out

where they have been and where they are going. What are the current issues and who are the major

players?

7. What have you done to improve your knowledge in the last year?

Try to include improvement activities that relate to the job. A wide variety of activities can be

mentioned as positive self-improvement. Have some good ones handy to mention.

8. Are you applying for other jobs?

Be honest but do not spend a lot of time in this area. Keep the focus on this job and what you can do

for this organization. Anything else is a distraction.

9. Why do you want to work for this organization?

This may take some thought and certainly, should be based on the research you have done on the

organization. Sincerity is extremely important here and will easily be sensed. Relate it to your long-

term career goals.

10. Do you know anyone who works for us?

Be aware of the policy on relatives working for the organization. This can affect your answer even

though they asked about friends not relatives. Be careful to mention a friend only if they are well

thought of.

11. What kind of salary do you need?

A loaded question. A nasty little game that you will probably lose if you answer first. So, do not

answer it. Instead, say something like, That's a tough question. Can you tell me the range for this

position? In most cases, the interviewer, taken off guard, will tell you. If not, say that it can depend

on the details of the job. Then give a wide range.

12. Are you a team player?

You are, of course, a team player. Be sure to have examples ready. Specifics that show you often

perform for the good of the team rather than for yourself are good evidence of your team attitude. Do

not brag, just say it in a matter-of-fact tone. This is a key point.

13. How long would you expect to work for us if hired?

Specifics here are not good. Something like this should work: I'd like it to be a long time. Or As long

as we both feel I'm doing a good job.

14. Have you ever had to fire anyone? How did you feel about that?

This is serious. Do not make light of it or in any way seem like you like to fire people. At the same

time, you will do it when it is the right thing to do. When it comes to the organization versus the

individual who has created a harmful situation, you will protect the organization. Remember firing is

not the same as layoff or reduction in force.

15. What is your philosophy towards work?

The interviewer is not looking for a long or flowery dissertation here. Do you have strong feelings

that the job gets done? Yes. That's the type of answer that works best here. Short and positive,

showing a benefit to the organization.

16. If you had enough money to retire right now, would you?

Answer yes if you would. But since you need to work, this is the type of work you prefer. Do not say

yes if you do not mean it.

17. Have you ever been asked to leave a position?

If you have not, say no. If you have, be honest, brief and avoid saying negative things about the

people or organization involved.

18. Explain how you would be an asset to this organization.

You should be anxious for this question. It gives you a chance to highlight your best points as they

relate to the position being discussed. Give a little advance thought to this relationship.

19. Why should we hire you?

Point out how your assets meet what the organization needs. Do not mention any other candidates

to make a comparison.

20. Tell me about a suggestion you have made.

Have a good one ready. Be sure and use a suggestion that was accepted and was then considered

successful. One related to the type of work applied for is a real plus.

21. What irritates you about co-workers?

This is a trap question. Think real hard but fail to come up with anything that irritates you. A short

statement that you seem to get along with folks is great.

22. What is your greatest strength?

Numerous answers are good, just stay positive. A few good examples: Your ability to prioritize, Your

problem-solving skills, Your ability to work under pressure, Your ability to focus on projects, Your

professional expertise, Your leadership skills, Your positive attitude

23. Tell me about your dream job.

Stay away from a specific job. You cannot win. If you say the job you are contending for is it, you

strain credibility. If you say another job is it, you plant the suspicion that you will be dissatisfied with

this position if hired. The best is to stay genetic and say something like: A job where I love the work,

like the people, can contribute and can't wait to get to work.

24. Why do you think you would do well at this job?

Give several reasons and include skills, experience and interest.

25. What are you looking for in a job?

See answer # 23

26. What kind of person would you refuse to work with?

Do not be trivial. It would take disloyalty to the organization, violence or lawbreaking to get you to

object. Minor objections will label you as a whiner.

27. What is more important to you: the money or the work?

Money is always important, but the work is the most important. There is no better answer.

28. What would your previous supervisor say your strongest point is?

There are numerous good possibilities:

Loyalty, Energy, Positive attitude, Leadership, Team player, Expertise, Initiative, Patience, Hard

work, Creativity, Problem solver

29. Tell me about a problem you had with a supervisor.

Biggest trap of all. This is a test to see if you will speak ill of your boss. If you fall for it and tell about

a problem with a former boss, you may well below the interview right there. Stay positive and

develop a poor memory about any trouble with a supervisor.

30. What has disappointed you about a job?

Don't get trivial or negative. Safe areas are few but can include:

Not enough of a challenge. You were laid off in a reduction Company did not win a contract, which

would have given you more responsibility.

31. Tell me about your ability to work under pressure.

You may say that you thrive under certain types of pressure. Give an example that relates to the

type of position applied for.

32. Do your skills match this job or another job more closely?

Probably this one. Do not give fuel to the suspicion that you may want another job more than this

one.

33. What motivates you to do your best on the job?

This is a personal trait that only you can say, but good examples are: Challenge, Achievement,

Recognition

34. Are you willing to work overtime? Nights? Weekends?

This is up to you. Be totally honest.

35. How would you know you were successful on this job?

Several ways are good measures:

You set high standards for yourself and meet them. Your outcomes are a success.Your boss tell you

that you are successful

36. Would you be willing to relocate if required?

You should be clear on this with your family prior to the interview if you think there is a chance it may

come up. Do not say yes just to get the job if the real answer is no. This can create a lot of problems

later on in your career. Be honest at this point and save yourself uture grief.

37. Are you willing to put the interests of the organization ahead of your own?

This is a straight loyalty and dedication question. Do not worry about the deep ethical and

philosophical implications. Just say yes.

38. Describe your management style.

Try to avoid labels. Some of the more common labels, like progressive, salesman or consensus, can

have several meanings or descriptions depending on which management expert you listen to. The

situational style is safe, because it says you will manage according to the situation, instead of one

size fits all.

39. What have you learned from mistakes on the job?

Here you have to come up with something or you strain credibility. Make it small, well intentioned

mistake with a positive lesson learned. An example would be working too far ahead of colleagues on

a project and thus throwing coordination off.

40. Do you have any blind spots?

Trick question. If you know about blind spots, they are no longer blind spots. Do not reveal any

personal areas of concern here. Let them do their own discovery on your bad points. Do not hand it

to them.

41. If you were hiring a person for this job, what would you look for?

Be careful to mention traits that are needed and that you have.

42. Do you think you are overqualified for this position?

Regardless of your qualifications, state that you are very well qualified for the position.

43. How do you propose to compensate for your lack of experience?

First, if you have experience that the interviewer does not know about, bring that up: Then, point out

(if true) that you are a hard working quick learner.

44. What qualities do you look for in a boss?

Be generic and positive. Safe qualities are knowledgeable, a sense of humor, fair, loyal to

subordinates and holder of high standards. All bosses think they have these traits.

45. Tell me about a time when you helped resolve a dispute between others.

Pick a specific incident. Concentrate on your problem solving technique and not the dispute you

settled.

46. What position do you prefer on a team working on a project?

Be honest. If you are comfortable in different roles, point that out.

47. Describe your work ethic.

Emphasize benefits to the organization. Things like, determination to get the job done and work hard

but enjoy your work are good.

48. What has been your biggest professional disappointment?

Be sure that you refer to something that was beyond your control. Show acceptance and no negative

feelings.

49. Tell me about the most fun you have had on the job.

Talk about having fun by accomplishing something for the organization.

50. Do you have any questions for me?

Always have some questions prepared. Questions prepared where you will be an asset to the

organization are good. How soon will I be able to be productive? and What type of projects will I be

able to assist on? are examples.