31. 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 mentioned
Answer: D
The input analog signal is converted into digital using an A/D converter and passed through DSP and then converted back to analog using a D/A converter.
32. Which of the following block is not required in the digital processing of a RADAR signal?
A. A/D converter
B. D/A converter
C. DSP
D. All of the mentioned
Answer: B
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 paper. So, there is no need for a D/A converter in this case.
33. Which of the following wave is known as the “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)/dt
Answer: C
The multiplicative operation is often encountered in analog communication, where an audio frequency signal is multiplied by a high-frequency sinusoid known as a carrier. The resulting signal is known as an “amplitude modulated wave”.
34. What is the physical device that performs an operation on the signal?
A. Signal source
B. System
C. Medium
D. None of the mentioned
Answer: B
A system is a physical device that performs the operation on the signal and modifies the input signal.
35. Which of the following is done to convert a continuous-time signal into a discrete-time signal?
A. Modulating
B. Sampling
C. Differentiating
D. Integrating
Answer: B
A discrete-time signal can be obtained from a continuous-time signal by replacing t with nT, where T is the reciprocal of the sampling rate or time interval between the adjacent values. This procedure is known as sampling.
36. The deflection voltage of an oscilloscope is a ‘deterministic’ signal.
A. True
B. False
Answer: A
The behavior of the signal is known and can be represented by a sawtooth waveform. So, the signal is deterministic.
37. 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))
Answer: C
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)).
38. Which of the following is the odd component of the signal x(t)=e(jt)?
39. 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)
Answer: D
For a continuous-time signal x(t) to be periodic with a period T, then x(t+mT) should be equal to x(t). 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.
40. 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 × T2
Answer: C
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.
41. 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 T1 and T2
C. Product of T1 and T2
D. Ratio of T1 to T2
Answer: A
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.
42. All energy signals will have an average power of ___________
A. Infinite
B. Zero
C. Positive
D. Cannot be calculated
Answer: B
For any energy signal, the average power should be equal to 0 i.e., P=0.
43. 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 mentioned
Answer: A
The energy signal should have a total energy value that lies between 0 and infinity.
44. What is the period of cos2t+sin3t?
A. π
B. 2 × π
C. 3 × π
D. 4 × π
Answer: B
Period of cos2t=(2 × π)/2=π
Period of sin3t=(2 × π)/3
LCM of π and (2 × π)/3 is 2 × π.
