Digital Signal Processing Mid  I, September  2014
1.An LTI Discrete time system is causal if and only if

h(n)≠0 for n<0

h(n)=0 for n<0

h(n)≠ for n<0

h(n)≠0 for n>0

Answer: B
2.For Energy signals, the energy will be finite and the average power will be _______

Infinite

finite

zero

can not be defined

Answer: C
3.Identify the dynamic system

y(n) = ax^{2}(n)

y(n) = ax(n)

y(n) = ax^{2}(n) + x(n)

y(n) = x(n)+x(n1)

Answer: C
4.Linear convolution of two sequences N1 and N2 produces an output sequence of length

N_{1} – N_{2} +1

N_{1} + N_{2} –1

N_{1} + N_{2} +1

2N_{1} – N_{2} +1

Answer: B
5.In NPoint DFT of L point Sequence, the value of N to avoid aliasing in frequency spectrum is

N≠L

N≤L

N≥L

N=L

Answer: C
6.In an Npoint sequence, if N=16 the total number of complex additions and multiplications using Radix2 FFT are

64 & 80

80 & 64

24 & 12

64 & 32

Answer: D
7.The complex valued phase factor/twiddle factor, WN can be represented as

e^{j2πN}

e^{j2π/N}

e^{j2π}

e^{j2πNK}

Answer: B
8.The ZTransform is a

Finite series

Infinite power series

Geometric series

Both a & c

Answer: B
9.The ROC of the signal x(n) = a^{n} for 5 < n < 5 is

Entire Zplane

Entire zPlane expect Z = 0 and Z =

Entire Zplane expect z = 0

Entire Zplane expect z =

Answer: B
10.Find the convolutions of the two signals x(n) = { 3, 2,1, 2} h(n) = {1, 2, 1, 2} is

y(n)={3,8,8,12,9,4,4}

y(n)={3,8,8,12,4,4,2}

y(n)={3,8,12,9,4,4}

y(n)={3,8,8,1,1,4,4}

Answer: A
11.A system is set to be _______________if the output doesn’t depends on future inputs and output.
Answer: Static (or) memory less
12.Appending zeros to a sequence in order to increase its length is called ______________
Answer: Zero padding
13.In _______________ method the overlapped samples in one of the output sequences are discarded.
Answer: Overlap save
14.If DFT of x(n) is X(K) then DFT ( Img x(n) ) is _______________
Answer: ½[x(K)x*(NK)]
15.The Npoint IDFT of X(K) is x(n) is equal to _______________
Answer:
16.The Twiddle factor W_{N} ^{K} is given by __________________
Answer: e^{j2π/N}
17.The _______________ of X(Z) is the set of all values of Z, for which X(Z) attains final value.
Answer: ROC
18.The ZTransform and ROC of an u(n) is ______________ and ______________
Answer: Z/Za, łZł > łał
19.The ___________________ signals are represented by DFS.
Answer: Sine
20.The digital signal processing involves ______________ signals and ____________ systems.
Answer: Digital (or) discrete, Discrete time