This set of Analog Communications Multiple Choice Questions & Answers (MCQs) focuses on “FM Receiver”.

1. What is the auto-correlation function of a signal (t) at t0=0?
a) It is equal to average voltage of the signal
b) It is equal to average power of the signal
c) It is equal to zero
d) It is equal to infinite

Explanation: Auto-correlation function is also known as serial-correlation. It is the correlation of a function with a delayed copy of itself. So it is non-unique description of signals. For a signal (t) at t0=0, it is equal to the average power of the signal.

2. The auto-correlation function is _________
a) impulse function
b) linear function
c) odd function
d) even function

Explanation: Auto-correlation is an even function. Sometimes it is also known as serial-correlation. It is the correlation of a function with a delayed copy of itself.

3. A signal is called ergodic if all type of ensemble averages are constant.
a) True
b) False

Explanation: A random signal is ergodic if time averages equals ensemble averages. Thus, if all type of ensemble averages can be interchanged.

4. A ransom signal is defined as ergodic, if ________
a) all type of ensemble averages are interchangeable
b) all type of ensemble averages are not interchangeable
c) all type of ensemble averages are constant
d) all type of ensemble averages are double than their previous value

Explanation: A stochastic process is said to be ergodic if its properties can be reduced from a single. A non ergodic process changes erratically at an inconsistent rate. Ergodic process exists if many random signals have identical time and ensemble averages. Thus, if all type of ensemble averages can be interchanged.

5. Which statement is correct about ergodic process?
a) ensemble and time averages are different
b) ensemble and time averages are opposite to each other
c) ensemble and time averages are identical
d) ensemble average are exactly twice of time averages

Explanation: A stochastic process is said to be ergodic if its properties can be reduced from a single. A non ergodic process changes erratically at an inconsistent rate. Ergodic process exists if many random signals have identical time and ensemble averages.
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6. Communication consists of electrical means of sending information only.
a) True
b) False

Explanation: Communication consists of means of sending, receiving and processing information via electromagnetic waves.

7. In communication system, redundancy ________
a) Helps to detect error
b) Helps to correct error
c) Reduces efficiency of communication
d) Helps to detect and correct error and also reduces efficiency

Explanation: Redundancy helps in many ways in communication. It not only helps to detect an error but also helps in correcting it. It sometimes reduces efficiency also. It is basically the duplication or can say that it is the backup of some important components, so as to efficiently detect the code, with the intention of increasing reliability of the system.

8. Which statement is true about emitter modulator amplifier for amplitude modulation?
a) operates in class A mode
b) operates in class C mode
c) operates in class B mode
d) operates in class D mode

Explanation: Emitter modulator amplifier for AM operates in class A mode and also has very low efficiency. The output of this modulator is very small and therefore it is not suitable for modulation at a high level.

Sanfoundry Global Education & Learning Series – Analog Communications.