Analog Communication

All Q&A

The maximum deviation allowed in an FM broadcast system is 75 kHz. If the modulating signal is a single tone sinusoid of 10 kHz, find the bandwidth of the FM signal. What will be the change in the bandwidth, if the modulating frequency is double? Determine the bandwidth when modulating signal amplitude is also double.

27 December, 2024

Given that ∆f=75KHz and fm=10KHz According to the Carson’s thumb rule the bandwidth BW=2(∆f+fm )=2(75+10)=170KHz

1. a. State sampling theorem. What is Nyquist rate of sampling?

b. What is pulse amplitude modulation

c. What is meant by flat top sampling? Why is it more preferred than natural sampling?

d. Explain the demodulation of PAM signal using a hold circuit

e. What is the bandwidth required for transmission of PAM signal?

27 December, 2024

a. The sampling theorem state that A band limited signal of finite energy, which has no frequency components higher than fm Hz, is completely described by its sampled values less than or equal to 1/(2fm ) second apart.

How is a Phase Locked Loop (PLL) used for demodulation of FM signal? Mention the advantage of PLL demodulation.

27 December, 2024

The PLL is useful in demodulation of FM signals in presence of large noise and low signal power (low signal to noise ratio). It is most switched for using space vehicle to earth data links or where loss along the transmission path is very large recently it has found application is commercial FM receivers.

Explain with suitable block diagram the generation of FM signal using Armstrong method.

27 December, 2024

The generation of FM waveform by indirect method is also known as Armstrong Method. In the indirect method a narrow band FM signal is generated first after that this NBFM signal is frequency multiplied to generate WBFM.

State Channel capacity theorem

27 December, 2024

Bandwidth and noise power place a restriction upon the rate of information that can be transmitted by a channel.

What is meant by entropy of a source?

27 December, 2024

In a practical communication system, we usually transmit long sequence of symbols from an information source. Thus we are more interested in the average information that a source produces than the information contain of a single symbol.

Apply Shannon – Fano algorithm to the source with M = 8 emitting message A, B, C, D, E, F, G, H having probability P(A) = 1/2, P(B) = P(C) = 1/8, P(D) = P(E) = P(F) = 1/16, P(G) = P(H) = 1/32, calculate entropy, average code length and efficiency of coding.

27 December, 2024

Given that the probabilities of the eight messages are respectively P(A) = 1/2, P(B) = P(C) = 1/8, P(D) = P(E) = P(F) = 1/16, P(G) = P(H) = 1/32