# Multiple Choice Questions and Answers on Digital Signal Processing(Part-1)

**1) The interface between an analog signal and a digital processor is**

**a.** D/A converter

**b.** A/D converter

**c.** Modulator

**d.** Demodulator

**ANSWER: (b) A/D converter**

**2) The speech signal is obtained after**

**a.** Analog to digital conversion

**b.** Digital to analog conversion

**c.** Modulation

**d.** Quantization

**ANSWER: (b) Digital to analog conversion**

**3) Telegraph signals are examples of**

**a.** Digital signals

**b.** Analog signals

**c.** Impulse signals

**d.** Pulse train

**ANSWER: (a) Digital signals**

**4) As compared to the analog systems, the digital processing of signals allow**

1) Programmable operations

2) Flexibility in the system design

3) Cheaper systems

4) More reliability

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1, 2 and 4 are correct

**d.** All the four are correct

**ANSWER: (d) All the four are correct**

**5) The Nyquist theorem for sampling**

1) Relates the conditions in time domain and frequency domain

2) Helps in quantization

3) Limits the bandwidth requirement

4) Gives the spectrum of the signal

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1 and 3 are correct

**d.** All the four are correct

**ANSWER: (c) 1 and 3 are correct**

**6) Roll-off factor is **

**a.** The bandwidth occupied beyond the Nyquist Bandwidth of the filter

**b.** The performance of the filter or device

**c.** Aliasing effect

**d.** None of the above

**ANSWER: (a) The bandwidth occupied beyond the Nyquist Bandwidth of the filter**

**7) A discrete time signal may be**

1) Samples of a continuous signal

2) A time series which is a domain of integers

3) Time series of sequence of quantities

4) Amplitude modulated wave

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1 and 3 are correct

**d.** All the four are correct

**ANSWER: (a) 1, 2 and 3 are correct**

**8) The discrete impulse function is defined by**

**a.** δ(n) = 1, n ≥ 0

= 0, n ≠ 1

**b.** δ(n) = 1, n = 0

= 0, n ≠ 1

**c.** δ(n) = 1, n ≤ 0

= 0, n ≠ 1

**d.** δ(n) = 1, n ≤ 0

= 0, n ≥ 1

**ANSWER: (b) δ(n) = 1, n = 0
= 0, n ≠ 1**

**9) DTFT is the representation of **

**a.** Periodic Discrete time signals

**b.** Aperiodic Discrete time signals

**c.** Aperiodic continuous signals

**d.** Periodic continuous signals

**ANSWER:(b) Aperiodic Discrete time signals**

**10) The transforming relations performed by DTFT are**

1) Linearity

2) Modulation

3) Shifting

4) Convolution

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1 and 3 are correct

**d.** All the four are correct

**ANSWER: (d) All the four are correct**

**11) The DFT is preferred for**

1) Its ability to determine the frequency component of the signal

2) Removal of noise

3) Filter design

4) Quantization of signal

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1 and 3 are correct

**d.** All the four are correct

**ANSWER: (c) 1 and 3 are correct**

**12) Frequency selectivity characteristics of DFT refers to**

**a.** Ability to resolve different frequency components from input signal

**b.** Ability to translate into frequency domain

**c.** Ability to convert into discrete signal

**d.** None of the above

**ANSWER: (a) Ability to resolve different frequency components from input signal**

**13) The Cooley–Tukey algorithm of FFT is a **

**a.** Divide and conquer algorithm

**b.** Divide and rule algorithm

**c.** Split and rule algorithm

**d.** Split and combine algorithm

**ANSWER: (a) Divide and conquer algorithm**

**14) FFT may be used to calculate**

1) DFT

2) IDFT

3) Direct Z transform

4) In direct Z transform

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1 and 3 are correct

**d.** All the four are correct

**ANSWER: (b) 1 and 2 are correct**

**15) DIT algorithm divides the sequence into**

**a.** Positive and negative values

**b.** Even and odd samples

**c.** Upper higher and lower spectrum

**d.** Small and large samples

**ANSWER: (b) Even and odd samples**

**16) The computational procedure for Decimation in frequency algorithm takes **

**a.** Log2 N stages

**b.** 2Log2 N stages

**c.** Log2 N^{2} stages

**d.** Log2 N/2 stages

**ANSWER:(a) Log2 N stages**

**17) The transformations are required for**

1) Analysis in time or frequency domain

2) Quantization

3) Easier operations

4) Modulation

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 1 and 3 are correct

**d.** All the four are correct

**ANSWER: (c) 1 and 3 are correct**

**18) The s plane and z plane are related as**

**a.** z = e^{sT}

**b.** z = e^{2sT}

**c.** z = 2e^{sT}

**d.** z = e^{sT}/2

**ANSWER: (a) z = e ^{sT}**

**19) The similarity between the Fourier transform and the z transform is that**

**a.** Both convert frequency spectrum domain to discrete time domain

**b.** Both convert discrete time domain to frequency spectrum domain

**c.** Both convert analog signal to digital signal

**d.** Both convert digital signal to analog signal

**ANSWER: (b) Both convert discrete time domain to frequency spectrum domain**

**20) The ROC of a system is the **

**a.** range of z for which the z transform converges

**b.** range of frequency for which the z transform exists

**c.** range of frequency for which the signal gets transmitted

**d.** range in which the signal is free of noise

**ANSWER: (a) range of z for which the z transform converges**

**21) The several ways to perform an inverse Z transform are**

1) Direct computation

2) Long division

3) Partial fraction expansion with table lookup

4) Direct inversion

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 2 and 3 are correct

**d.** All the four are correct

**ANSWER: (d) All the four are correct**

**22) The anti causal sequences have ______ components in the left hand sequences.**

**a.** Positive

**b.** Negative

**c.** Both a and b

**d.** None of the above

**ANSWER: (a) Positive**

**23) For an expanded power series method, the coefficients represent**

**a.** Inverse sequence values

**b.** Original sequence values

**c.** Negative values only

**d.** Positive values only

**ANSWER: (a) Inverse sequence values**

**24) The region of convergence of x/ (1+2x+x ^{2}) is**

**a.** 0

**b.** 1

**c.** Negative

**d.** Positive

**ANSWER: (b) 1**

**25) The IIR filter designing involves **

**a.** Designing of analog filter in analog domain and transforming into digital domain

**b.** Designing of digital filter in analog domain and transforming into digital domain

**c.** Designing of analog filter in digital domain and transforming into analog domain

**d.** Designing of digital filter in digital domain and transforming into analog domain

**ANSWER: (b) Designing of digital filter in analog domain and transforming into digital domain**

**26) For a system function H(s) to be stable**

**a.** The zeros lie in left half of the s plane

**b.** The zeros lie in right half of the s plane

**c.** The poles lie in left half of the s plane

**d.** The poles lie in right half of the s plane

**ANSWER: (c) The poles lie in left half of the s plane**

**27) IIR filter design by approximation of derivatives has the limitations**

1) Used only for transforming analog high pass filters

2) Used for band pass filters having smaller resonant frequencies

3) Used only for transforming analog low pass filters

4) Used for band pass filters having high resonant frequencies

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 2 and 3 are correct

**d.** All the four are correct

**ANSWER: (c) 2 and 3 are correct**

**28) The filter that may not be realized by approximation of derivatives techniques are**

1) Band pass filters

2) High pass filters

3) Low pass filters

4) Band reject filters

**a.** 1, 2 and 3 are correct

**b.** 2 and 4 are correct

**c.** 2 and 3 are correct

**d.** All the four are correct

**ANSWER: (b) 2 and 4 are correct**

**29) In direct form for realisation of IIR filters,**

1) Denominator coefficients are the multipliers in the feed forward paths

2) Multipliers in the feedback paths are the positives of the denominator coefficients

3) Numerator coefficients are the multipliers in the feed forward paths

4) Multipliers in the feedback paths are the negatives of the denominator coefficients

**a.** 1, 2 and 3 are correct

**b.** 1 and 2 are correct

**c.** 3 and 4 are correct

**d.** All the four are correct

**ANSWER:(c) 3 and 4 are correct**

**30) The direct form II for realisation involves**

1) The realisation of transfer function into two parts

2) Realisation after fraction

3) Product of two transfer functions

4) Addition of two transfer functions

**a.** 1, 2 and 3 are correct

**b.** 1 and 3 are correct

**c.** 3 and 4 are correct

**d.** All the four are correct

**ANSWER: (b) 1 and 3 are correct**

**31) The cascade realisation of IIR systems involves**

1) The transfer function broken into product of transfer functions

2) The transfer function divided into addition of transfer functions

3) Factoring the numerator and denominator polynomials

4) Derivatives of the transfer functions

**a.** 1, 2 and 3 are correct

**b.** 1 and 3 are correct

**c.** 3 and 4 are correct

**d.** All the four are correct

**ANSWER:(b) 1 and 3 are correct**

**32) The advantage of using the cascade form of realisation is**

1) It has same number of poles and zeros as that of individual components

2) The number of poles is the product of poles of individual components

3) The number of zeros is the product of poles of individual components

4) Over all transfer function may be determined

**a.** 1, 2 and 3 are correct

**b.** 1 and 3 are correct

**c.** 1 and 4 are correct

**d.** All the four are correct

**ANSWER: (c) 1 and 4 are correct**

**33) Which among the following represent/s the characteristic/s of an ideal filter?**

**a.** Constant gain in passband

**b.** Zero gain in stop band

**c.** Linear Phase Response

**d.** All of the above

**ANSWER: (d) All of the above**

**34) FIR filters ________**

A. are non-recursive

B. do not adopt any feedback

C. are recursive

D. use feedback

**a.** A & B

**b.** C & D

**c.** A & D

**d.** B & C

**ANSWER:(a) A & B**

**35) In tapped delay line filter, the tapped line is also known as ________**

**a.** Pick-on node

**b.** Pick-off node

**c.** Pick-up node

**d.** Pick-down node

**ANSWER:(b) Pick-off node**

**36) How is the sensitivity of filter coefficient quantization for FIR filters?**

**a.** Low

**b.** Moderate

**c.** High

**d.** Unpredictable

**ANSWER: (a) Low**

**37) Decimation is a process in which the sampling rate is __________.**

**a.** enhanced

**b.** stable

**c.** reduced

**d.** unpredictable

**ANSWER:(c) reduced**

**38) Anti-imaging filter with cut-off frequency ω _{c} = π/ I is specifically used _______ upsampling process for the removal of unwanted images.**

**a.** Before

**b.** At the time of

**c.** After

**d.** All of the above

**ANSWER: (c) After**

**39) Which units are generally involved in Multiply and Accumulate (MAC)?**

**a.** Adder

**b.** Multiplier

**c.** Accumulator

**d.** All of the above

**ANSWER: (d) All of the above**

**40) In DSP processors, which among the following maintains the track of addresses of input data as well as the coefficients stored in data and program memories?**

**a.** Data Address Generators (DAGs)

**b.** Program sequences

**c.** Barrel Shifter

**d.** MAC

**ANSWER: (a) Data Address Generators (DAGs)**