 MORE IN Digital Communication
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INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any one question from Q.1(a,b,c) &Q.2(a,b,c)
1(a) Derive the Expession for quantization error and signal to quantization noise ratio for a non-sinusoidal PCM system.
6 M
1(b) Draw AT and T hierarchy multiplexing system and explain.
8 M
1(c) Explain narrowband noise and represent a narrowband noise in terms in inphase and quadrature components.
6 M

2(a) A delta modualtor system is designed to operate 5 times the Nyquist rate for a signal with 3KHz bandwidth. Determine the maximum amplitude of 1.2KHz input sinusoid for which a delta modualtor does not have slope overload. Quantizing step size size is 250mV. Derive the expression used.
6 M
2(b) Ascrambler is shown in figure 1. design the corresponding scrambles. If a sequence. S= 101010100000111 is applied to the input of his scrambles, determine the output sequence T. Verify that if this T is applied to te input of the descrambles, the output is the sequence S.
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8 M
2(c) Explain classification random process with mathematical expressions.
6 M

Solve any one question from Q.3(a,b) &Q.4(a,b)
3(a) Derive the expression of signal to noise ratio (S/N) of integrator and dump filter, explain its operation.
8 M
3(b) A polar NRZ signal is applied at the input of matched filter. The binary 1 is represented by reactangular pulses of amplitude A and duration T and the binary 0 is represented by reactangular pulse of amplitude -A and duration T. Obtain the impulse reponse of the matched filter and sketch it.
8 M

4(a) Derive the expression for signal to noise ratio and error probability of a mathced filter is the presence of white Gaussian noise.
8 M
4(b) Explain Geometrical representation of signal and Gram-Schmitt procedure.
8 M

Solve any one question from Q.5(a,b) &Q.6(a,b)
5(a) Derive the expression for error probability of BPSK receiver.
8 M
5(b) Give the mathematical representation of QPSK signal. Draw the signal space diagram of QPSK signal. Write the expression of all the message points in the diagram and explain.
8 M

6(a) Explain M-ary PSK transmitter and receiver with suitable block dirgam. What are the advantages of M-ary PSK over M-ary FSK?
8 M
6(b) Binary data is transmitted using BPSK at a rate 2 Mbps over RF link having bandewidth 2 MHz. Find signal power required at receiver input so taht error probability is less than or equal to 10-4. Assume noise PSD to be 10-10 watt/Hz. (Q(3.71)=10-4).
8 M

Solve any one question from Q.7(a,b,c) &Q.8(a,b,c)
7(a) What is PN sequence? Explain the three properties of PN sequence with the help of 4 stage shift register.
6 M
7(b) Draw the block diagram of DSSS system transmitter and receives. Write functional names inside the block and iput signal for each block & explain.
6 M
7(c) What are the multiple access techinques? Explain WODMA in detail.
6 M

8(a) Explain DS-SS BPSK transmittes and receiver with suitable block diagram and derive the power spectral density of the same.
6 M
8(b) Explain the following frequency hop spread spectrum with the help of relevent diagram.
i) Slow frequency hopping.
ii) Fast frequency hopping.
6 M
8(c) Design a three feedback shift register with proper taps to generate N=7 PN sequence. Dra the generator block and if the initial state of shift register is 100 (fromleft to right). Find the output sequence.
6 M

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