Communication Systems

Determine the carrier swing the highest and the lowest frequencies attained, and the modulation index of the FM signal generated by frequency modulating a 101.6 MHz carrier with an 8 kHz sine wave causing a frequency deviation of 40 kHz.

An AM radio transmitter gives a power output of 5 kW when modulated to a depth of 95%. If after modulation by a speech signal which produces an average modulation depth of 20%, the carrier and one sideband are suppressed, determine the average power in remaining output. 

a) Discuss the types, causes and effects of the various forms of noise- which may be created within an amplifier. 

(b) State important properties of CDF and explain them.

(c) Derive an expression of a Frequency Modulated Wave with spectrum.

(d) What is the difference between narrowband and Wideband FM.

(e) Find the bandwidth required for a Gaussian modulated wideband FM Signal. Explain the difference between wide sense stationary and strict sense stationary processes.

a) With the help of block diagram explain communication system model. List the advantages and disadvantages of Digital Communication 

b) What is Double sideband suppressed carrier system?Discuss two types of a product modulator. 

a) Derive an expression for a single-tone narrowband frequency-modulatedwave. List the difference between narrowband FM and wideband FM

a) What is PAM? With the help of sample and hold circuit explain the its working principle. List some drawbacks of PAM signal.

Compare Delta rodulation(DM), Adaptive Delta Modulation(ADM) and PCM techniques. 

Draw the block diagram of QPSK system and explain its working. Write and draw the power spectral density of QPSK signals. 

 What is meant by "Noise" in communication system? Explain the following term

i) Signal to Noise ratio

 What is meant by "Noise" in communication system? Explain the following term

ii) Noise Figure

 What is meant by "Noise" in communication system? Explain the following term

ii) Noise Temperature

Define the following term:

i) Code word 

Define the following term:

ii) Block length

Define the following term:

i) Code rate

Define the following term:

iv) Channel data rate

Define the following term:

v) Code vectors

e) List the steps for determining all the codewords for a Linear Block Code.

What are the fundamental limitations in Communication system? Why is modulation of signal required for transmission? 

For a system  where M(t) is random with E[M(t)]=0 and E[M²(t)] =M₀ Find 

(i) If random variable  is zero find E(Z²). Is random process a stationary random process. (ii) If  is an independent random variable having a uniform PDF between  and  , find E[Z²]. Is the process now a stationary process. 

In any communication system, the signal has following double sided exponential PDF.

Find

(i) Relation between the constant a and b

(ii) Assuming a=3; find the average value, dc power, ac power and total power contained in given random signal.

(iii) Probability distribution function and cumulative distribution function.

(iv) Total probability that random variable x lies between -1 and +2 .

Explain the phase shift method of SSB generation. List its advantages & disadvantages with respect to the other methods of generation.

Draw the block diagram of super hetrodyne receiver and explain.

Starting with an oscillator working near 500 kHz and using a maximum frequency deviation not exceeding   at the frequency, calculate the following for an Armstrong system which is to yield a center frequency precisely 97 MHz with a deviation of exactly 75 kHz:

(a) starting frequency;

b) exact initial deviation;

(c) frequency of the crystal oscillator;

(d) amount of frequency multiplication in each group. 

Explain the noise analysis of DSB-SC receiver using coherent detection and derive the expression of figure of merit.

Evaluate the condition for distortion less demodulation of a VSB signal, initially generated by passing a DSB signal through a VSB filter, using synchronous detector. 

A rule of BW for FM signal is sometimes used as BW=(2m₁+1)f_m Find the fraction of the signal power that is included in the frequency band. Assume m₁=1 & 10.

Compare PM and FM

Prove that in an FM system the output SNR, assuming sinusoida lmodulation, is given by by   . Where m is the modulation index for FM.

Write short note on:

a) Pre-emphasis and De-emphasis

b) Thermal noise 

 Represent the binary data sequence 0110100011 in the following formats:

i) Non-return-to-zoro unipolar format 

 Write a note on Quadrature carrier multiplexing.

Consider the message signal m(t)= 20 cos2 volts and carrier wave  = 50 cos100 volts.

(i) Give time-domain expression for the resulting conventional AM wave for 75% Modulation

Consider the message signal m(t)=20 cos2t volts and carrier wave  =50 cos100nt volts.

(ii) Find the power developed across a load of 100 due to this am wave.

a. Explain frequency discrimination method for generating SSB modulated wave.

 Assume that an AM receiver with an envelope detector is tuned to a SSB signal that has a modulation waveform given by m(t). Find the mathematical expression for audio signal that appears at the receiver output in terms of m(t) 

c. Discuss frequency division multiplexing with block diagram. 

a. What is angle modulation? With expressions, explain the commonly used methods.

b. Describe the direct method of FM generation with circuit and expressions.

With block diagram, explain FM stereo multiplexing.

With necessary expressions, discuss pre-emphasis and de-emphasis in a FM system.

a. Give the block diagram of digital communication system. Explain the function of each block.

b. Write a detailed note on Delta modulation.

b. Explain Time division multiplexing system with block diagram.

c. Describe the sample and hold circuit for signal recovery.

With circuit diagram, explain the generation of AM waves using square law modulator.

Represent the binary data sequence 0110100011 in the following formats:

ii) Non-return-to-zero polar format  

Represent the binary data sequence 0110100011 in the following format:

iii) Non-return-to-zero bipolar format

Represent the binary data sequence 0110100011 in the following format:

iv) Manchester format

b. Discuss eye pattern of data transmission system.

c. Give the generalized form of correlation coding scheme.

a. Describe the block diagram of a single channel telemetry system.

With an example, explain implantable telemetry system.

c. List the applications of telemedicine.

Find the Nyquist rate and Nyquist interval for the signal

a) Derive an expression for single-tone amplitude-modulated wave.

b) What is Carson's Rule? Define modulation index for FM?

c) State and prove sampling theorem in time domain.

d). Differentiate DPSK and QPSK techniques?