33 + Interview Questions in Dsp – Basic Signaling in Digital Signal Processing Page 1 InterviewSolution

1.	What is the physical device that performs an operation on the signal?(a) Signal source(b) System(c) Medium(d) None of the mentionedThis question was posed to me in examination.Asked question is from Signals, Systems and Signal Processing in portion DSP – Basic Signaling of Digital Signal Processing
Answer» RIGHT option is (b) SYSTEM Explanation: A system is a PHYSICAL device which PERFORMS the operation on the signal and modifies the INPUT signal.

Discussion

2.	Which of the following wave is known as “amplitude modulated wave” of x(t)?(a) C.x(t) (where C is a constant)(b) x(t)+y(t)(c) x(t).y(t)(d) dx(t)/dtThis question was posed to me during an online interview.I would like to ask this question from Signals, Systems and Signal Processing in portion DSP – Basic Signaling of Digital Signal Processing
Answer» Right option is (c) x(t).y(t) For explanation I would say: The multiplicative OPERATION is often ENCOUNTERED in analog communication, where an audio frequency signal is MULTIPLIED by a high frequency sinusoid known as carrier. The resulting signal is known as “AMPLITUDE modulated WAVE”.

Discussion

3.	Which of the following block is not required in digital processing of a RADAR signal?(a) A/D converter(b) D/A converter(c) DSP(d) All of the mentionedThis question was posed to me by my school teacher while I was bunking the class.My doubt stems from Signals, Systems and Signal Processing topic in portion DSP – Basic Signaling of Digital Signal Processing
Answer» CORRECT answer is (b) D/A converter For explanation: In the digital PROCESSING of the radar signal, the INFORMATION extracted from the radar signal, such as the position of the aircraft and its speed, may SIMPLY be printed on a PAPER. So, there is no need of an D/A converter in this case.

Discussion

4.	What are the important block(s) required to process an input analog signal to get an output analog signal?(a) A/D converter(b) Digital signal processor(c) D/A converter(d) All of the mentionedI have been asked this question in an interview for job.My question is based upon Signals, Systems and Signal Processing in division DSP – Basic Signaling of Digital Signal Processing
Answer» RIGHT option is (d) All of the mentioned Easy explanation: The INPUT analog signal is converted into DIGITAL using A/D CONVERTER and passed through DSP and then converted back to analog using a D/A converter.

Discussion

5.	If a signal x(t) is processed through a system to obtain the signal (x(t)^2), then the system is said to be ____________(a) Linear(b) Non-linear(c) Exponential(d) None of the mentionedThis question was posed to me in exam.The query is from Signals, Systems and Signal Processing topic in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» Correct answer is (b) Non-linear Best EXPLANATION: Let the input signal be ‘t’. Then the OUTPUT signal after passing through the SYSTEM is y=t^2 which is the equation of a parabola. So, the system is non-linear.

Discussion

6.	If x(n)=(0,0,1,1,1,1,1,0) then x(3n+1) is?(a) (0,1,0,0,0,0,0,0)(b) (0,0,1,1,1,1,0,0)(c) (1,1,0,0,0,0,0,0)(d) None of the mentionedThis question was addressed to me in a job interview.This interesting question is from Signals, Systems and Signal Processing topic in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» The correct choice is (a) (0,1,0,0,0,0,0,0) The best EXPLANATION: First shift the given signal left by 1 and then TIME scale the OBTAINED signal by 3.

Discussion

7.	If x(n)=(0,0,1,2,3,4,0,0) then x(n-2) is?(a) (0,0,2,4,6,8,0,0)(b) (0,0,1,2,3,4,0,0)(c) (1,2,3,4,0,0,0,0)(d) (0,0,0,0,1,2,3,4)This question was addressed to me in exam.My question comes from Signals, Systems and Signal Processing in portion DSP – Basic Signaling of Digital Signal Processing
Answer» Right CHOICE is (d) (0,0,0,0,1,2,3,4) To EXPLAIN: The SIGNAL x(N) is SHIFTED right by 2.

Discussion

8.	Which of the following is common independent variable for speech signal, EEG and ECG?(a) Time(b) Spatial coordinates(c) Pressure(d) None of the mentionedI got this question in an online quiz.My question is taken from Signals, Systems and Signal Processing topic in division DSP – Basic Signaling of Digital Signal Processing
Answer»

Discussion

9.	If x(n)=(0,1,2,3,3,0,0,0) then x(2n) is?(a) (0,2,4,6,6,0,0,0)(b) (0,1,2,3,3,0,0,0)(c) (0,2,3,0,0,0,0,0)(d) None of the mentionedI have been asked this question in my homework.The above asked question is from Signals, Systems and Signal Processing topic in division DSP – Basic Signaling of Digital Signal Processing
Answer» The correct CHOICE is (c) (0,2,3,0,0,0,0,0) EXPLANATION: SUBSTITUTE n=0,1,2… in x(2N) and obtain the values from the given x(n).

Discussion

10.	Which property does y(t)=x(1-t) exhibit?(a) Time scaling(b) Time shifting(c) Reflecting(d) Time shifting and reflectingI have been asked this question in an online quiz.I need to ask this question from Signals, Systems and Signal Processing topic in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» Correct option is (d) TIME shifting and REFLECTING To explain: First the signal x(t) is shifted by 1 to get x(1+t) and it is reflected to get x(1-t). So, it EXHIBITS both time shifting and reflecting properties.

Discussion

11.	Which of the following conditions made digital signal processing more advantageous over analog signal processing?(a) Flexibility(b) Accuracy(c) Storage(d) All of the mentionedI have been asked this question in homework.This interesting question is from Signals, Systems and Signal Processing in division DSP – Basic Signaling of Digital Signal Processing
Answer» Correct answer is (d) All of the mentioned The best I can explain: DIGITAL programmable system allows flexibility in reconfiguring the DSP OPERATIONS by just changing the program, as the digital SIGNAL is in the FORM of 1 and 0’s it is more accurate and it can be stored in magnetic tapes.

Discussion

12.	Let x1(t) and x2(t) be periodic signals with fundamental periods T1 and T2 respectively.Then the fundamental period of x(t)=x1(t)+x2(t) is?(a) LCM of T1 and T2(b) HCF of T1and T2(c) Product of T1 and T2(d) Ratio of T1 to T2The question was posed to me by my school principal while I was bunking the class.Asked question is from Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing
Answer» CORRECT answer is (a) LCM of T1 and T2 To explain: For the sum of x1(t) and x2(t) to be PERIODIC the RATIO of their periods should be a rational number, then the fundamental period is the LCM of T1 and T2.

Discussion

13.	What is the period of cos2t+sin3t?(a) pi(b) 2pi(c) 3pi(d) 4*piI got this question in my homework.Question is from Classification of Signals in division DSP – Basic Signaling of Digital Signal Processing
Answer» Right CHOICE is (B) 2pi Explanation: PERIOD of cos2t=(2pi)/2=pi Period of SIN3T=(2pi)/3 LCM of pi and (2pi)/3 is 2*pi.

Discussion

14.	x(t) or x(n) is defined to be an energy signal, if and only if the total energy content of the signal is a ___________(a) Finite quantity(b) Infinite(c) Zero(d) None of the mentionedThis question was addressed to me in examination.My enquiry is from Classification of Signals in division DSP – Basic Signaling of Digital Signal Processing
Answer»

Discussion

15.	All energy signals will have an average power of ___________(a) Infinite(b) Zero(c) Positive(d) Cannot be calculatedI got this question in homework.Origin of the question is Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing
Answer» Correct answer is (B) Zero The best EXPLANATION: For any energy signal, the average POWER should be equal to 0 i.e., P=0.

Discussion

16.	Let x1(t) and x2(t) be periodic signals with fundamental periods T1 and T2 respectively. Which of the following must be a rational number for x(t)=x1(t)+x2(t) to be periodic?(a) T1+T2(b) T1-T2(c) T1/T2(d) T1*T2This question was posed to me during an interview.This interesting question is from Classification of Signals in section DSP – Basic Signaling of Digital Signal Processing
Answer» Right option is (C) T1/T2 The explanation: Let T be the PERIOD of the signal x(t) =>x(t+T)=x1(t+mT1)+x2(t+nT2) THUS, we MUST have mT1=nT2=T =>(T1/T2)=(k/m)= a rational number.

Discussion

17.	For a continuous time signal x(t) to be periodic with a period T, then x(t+mT) should be equal to ___________(a) x(-t)(b) x(mT)(c) x(mt)(d) x(t)I had been asked this question in class test.My question comes from Classification of Signals in section DSP – Basic Signaling of Digital Signal Processing
Answer» RIGHT answer is (d) x(t) The EXPLANATION is: If a SIGNAL x(t) is said to be periodic with period T, then x(t+mT)=x(t) for all t and any integer m.

Discussion

18.	Which of the following is the odd component of the signal x(t)=e^(jt)?(a) cost(b) jsint(c) jcost(d) sintI got this question in a job interview.This interesting question is from Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing
Answer» The correct ANSWER is (B) Jsint To elaborate: Let x(t)=e^(JT) Now, xo(t)=(1/2)(x(t)-x(-t)) =(1/2)(e^(jt) – e^(-jt)) =(1/2)(cost+jsint-cost+jsint) =(1/2)(2jsint) =jsint.

Discussion

19.	The even part of a signal x(t) is?(a) x(t)+x(-t)(b) x(t)-x(-t)(c) (1/2)(x(t)+x(-t))(d) (1/2)(x(t)-x(-t))I got this question by my college director while I was bunking the class.This interesting question is from Classification of Signals in section DSP – Basic Signaling of Digital Signal Processing
Answer» Correct choice is (C) (1/2)(x(t)+x(-t)) The BEST I can EXPLAIN: Let x(t)=xe(t)+XO(t) =>x(-t)=xe(-t)-xo(-t) By adding the above two EQUATIONS, we get xe(t)=(1/2)(x(t)+x(-t)).

Discussion

20.	The deflection voltage of an oscilloscope is a ‘deterministic’ signal.(a) True(b) FalseI had been asked this question in unit test.My question is based upon Classification of Signals topic in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» RIGHT option is (a) True Easy EXPLANATION: The behavior of the signal is known and can be represented by a saw tooth wave form. So, the signal is DETERMINISTIC.

Discussion

21.	Which of the following is done to convert a continuous time signal into discrete time signal?(a) Modulating(b) Sampling(c) Differentiating(d) IntegratingI have been asked this question during an online exam.This intriguing question comes from Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing
Answer» The correct answer is (b) Sampling For EXPLANATION I would say: A discrete time signal can be obtained from a continuous time signal by replacing t by NT, where T is the reciprocal of the sampling rate or time INTERVAL between the adjacent values. This PROCEDURE is known as sampling.

Discussion

22.	Which bit coder is required to code a signal with 16 levels?(a) 8 bit(b) 4 bit(c) 2 bit(d) 1 bitThis question was addressed to me at a job interview.The doubt is from A2D and D2A Converters in section DSP – Basic Signaling of Digital Signal Processing
Answer» Correct answer is (b) 4 BIT The explanation is: To code a SIGNAL with L number of LEVELS, we require a CODER with (log L/log 2) number of bits. So, log16/log2=4 bit coder is required.

Discussion

23.	The quality of output signal from A/D converter is measured in terms of ___________(a) Quantization error(b) Quantization to signal noise ratio(c) Signal to quantization noise ratio(d) Conversion constantThis question was addressed to me in semester exam.I'm obligated to ask this question of A2D and D2A Converters topic in portion DSP – Basic Signaling of Digital Signal Processing
Answer» The correct answer is (c) Signal to quantization NOISE RATIO Explanation: The quality is measured by taking the ratio of NOISES of input signal and the quantized signal i.e., SQNR and is measured in TERMS of dB.

Discussion

24.	If the sampling rate Fs satisfies the sampling theorem, then the relation between quantization errors of analog signal(eq(t)) and discrete-time signal(eq(n)) is?(a) eq(t)=eq(n)(b) eq(t)eq(n)(d) not relatedThe question was posed to me in an internship interview.I want to ask this question from A2D and D2A Converters in portion DSP – Basic Signaling of Digital Signal Processing
Answer» RIGHT ANSWER is (a) eq(t)=eq(n) To explain I WOULD say: If it obeys sampling theorem, then the only ERROR in A/D CONVERSION is quantization error. So, the error is same for both analog and discrete-time signal.

Discussion

25.	What is the discrete-time signal obtained after sampling the analog signal x(t)=cos(2000pit)+sin(5000pit) at a sampling rate of 5000 samples/sec?(a) cos(2.5pin)+sin(pin)(b) cos(0.4pin)+sin(pin)(c) cos(2000pin)+sin(5000pin)(d) none of the mentionedThis question was addressed to me during an internship interview.My question comes from A2D and D2A Converters in section DSP – Basic Signaling of Digital Signal Processing
Answer» The correct choice is (b) COS(0.4pin)+sin(pin) Easy explanation: From the given ANALOG SIGNAL, F1=1000Hz F2=2500Hz and Fs=5000Hz =>f1=F1/Fs and f2=F2/Fs =>f1=0.2 and f2=0.5 =>x(n)=cos(0.4pin)+sin(pin).

Discussion

26.	What is the nyquist rate of the signal x(t)=3cos(50pit)+10sin(300pit)-cos(100pit)?(a) 50Hz(b) 100Hz(c) 200Hz(d) 300HzI got this question by my college professor while I was bunking the class.I'm obligated to ask this question of A2D and D2A Converters in portion DSP – Basic Signaling of Digital Signal Processing
Answer» RIGHT CHOICE is (d) 300Hz The best explanation: The FREQUENCIES present in the given signal are F1=25Hz, F2=150Hz, F3=50Hz Thus Fmax=150Hz and from the SAMPLING THEOREM, nyquist rate=2Fmax Therefore, Fs=2150=300Hz.

Discussion

27.	If ‘F’ is the frequency of the analog signal, then what is the minimum sampling rate required to avoid aliasing?(a) F(b) 2F(c) 3F(d) 4FThe question was posed to me in a national level competition.This interesting question is from A2D and D2A Converters topic in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» Correct option is (a) F For EXPLANATION: According to NYQUIST rate, to AVOID aliasing the sampling frequency should be equal to twice of the ANALOG frequency.

Discussion

28.	What is output signal when a signal x(t)=cos(2pi40t) is sampled with a sampling frequency of 20Hz?(a) cos(pin)(b) cos(2pin)(c) cos(4pin)(d) cos(8pin)I have been asked this question in an online quiz.I'd like to ask this question from A2D and D2A Converters in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» CORRECT answer is (C) COS(4pin) EXPLANATION: From the question F=40Hz, Fs=20Hz =>f=F/Fs =>f=40/20 =>f=2Hz =>x(n)=cos(4pin).

Discussion

29.	The relation between analog frequency ‘F’ and digital frequency ‘f’ is?(a) F=fT(where T is sampling period)(b) f=FT(c) No relation(d) None of the mentionedThe question was posed to me during an online exam.The question is from A2D and D2A Converters in division DSP – Basic Signaling of Digital Signal Processing
Answer» Correct choice is (b) f=FT Explanation: CONSIDER an analog SIGNAL of frequency ‘F’, which when SAMPLED PERIODICALLY at a rate Fs=1/T samples per second YIELDS a frequency of f=F/Fs=>f=FT.

Discussion

30.	The difference between the unquantized x(n) and quantized xq(n) is known as ___________(a) Quantization coefficient(b) Quantization ratio(c) Quantization factor(d) Quantization errorThis question was addressed to me by my school teacher while I was bunking the class.The doubt is from A2D and D2A Converters topic in division DSP – Basic Signaling of Digital Signal Processing
Answer» Right choice is (d) QUANTIZATION error Explanation: Quantization error is the DIFFERENCE in the signal obtained after sampling i.e., x(n) and the signal obtained after quantization i.e., xq(n) at any instant of TIME.

Discussion

31.	Which of the following is a digital-to-analog conversion process?(a) Staircase approximation(b) Linear interpolation(c) Quadratic interpolation(d) All of the mentionedI have been asked this question during an online exam.The doubt is from A2D and D2A Converters in chapter DSP – Basic Signaling of Digital Signal Processing
Answer» Correct option is (d) All of the mentioned Easiest explanation: The process of JOINING in terms of steps is known as staircase approximation, connecting two samples by a straight LINE is known as Linear INTERPOLATION, connecting three samples by fitting a quadratic curve is called as Quadratic interpolation.

Discussion

32.	The process of converting discrete-time continuous valued signal into discrete-time discrete valued (digital) signal is known as ____________(a) Sampling(b) Quantization(c) Coding(d) None of the mentionedI had been asked this question in semester exam.The doubt is from A2D and D2A Converters topic in portion DSP – Basic Signaling of Digital Signal Processing
Answer» Right CHOICE is (b) Quantization Easy explanation: In this process, the value of each signal sample is represented by a value selected from a FINITE set of possible VALUES. HENCE this process is known as ‘quantization’

Discussion

33.	Which of the following should be done in order to convert a continuous-time signal to a discrete-time signal?(a) Sampling(b) Differentiating(c) Integrating(d) None of the mentionedThe question was posed to me in an interview for internship.My query is from A2D and D2A Converters in portion DSP – Basic Signaling of Digital Signal Processing
Answer» CORRECT answer is (a) SAMPLING To explain: The process of converting a CONTINUOUS-time signal into a DISCRETE-time signal by taking samples of continuous time signal at discrete time instants is known as ‘sampling’.

Discussion

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If x(n)=(0,0,1,2,3,4,0,0) then x(n-2) is?(a) (0,0,2,4,6,8,0,0)(b) (0,0,1,2,3,4,0,0)(c) (1,2,3,4,0,0,0,0)(d) (0,0,0,0,1,2,3,4)This question was addressed to me in exam.My question comes from Signals, Systems and Signal Processing in portion DSP – Basic Signaling of Digital Signal Processing

What is the period of cos2t+sin3t?(a) pi(b) 2*pi(c) 3*pi(d) 4*piI got this question in my homework.Question is from Classification of Signals in division DSP – Basic Signaling of Digital Signal Processing

All energy signals will have an average power of ___________(a) Infinite(b) Zero(c) Positive(d) Cannot be calculatedI got this question in homework.Origin of the question is Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing

Which of the following is the odd component of the signal x(t)=e^(jt)?(a) cost(b) j*sint(c) j*cost(d) sintI got this question in a job interview.This interesting question is from Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing

The deflection voltage of an oscilloscope is a ‘deterministic’ signal.(a) True(b) FalseI had been asked this question in unit test.My question is based upon Classification of Signals topic in chapter DSP – Basic Signaling of Digital Signal Processing

Which bit coder is required to code a signal with 16 levels?(a) 8 bit(b) 4 bit(c) 2 bit(d) 1 bitThis question was addressed to me at a job interview.The doubt is from A2D and D2A Converters in section DSP – Basic Signaling of Digital Signal Processing

What is the period of cos2t+sin3t?(a) pi(b) 2pi(c) 3pi(d) 4*piI got this question in my homework.Question is from Classification of Signals in division DSP – Basic Signaling of Digital Signal Processing

Which of the following is the odd component of the signal x(t)=e^(jt)?(a) cost(b) jsint(c) jcost(d) sintI got this question in a job interview.This interesting question is from Classification of Signals in portion DSP – Basic Signaling of Digital Signal Processing