Solve any one question from Q1 and Q2

1 (a)
Explain with the help of block diagram formatting and transmission of baseband signal.

8 M

1 (b)
Define mean, correlation, standard deviation of a random process.

6 M

1 (c)
Draw the block diagram of DM transmitter and explain its working. Comment on the drawbacks of DM.

6 M

2 (a)
Define the terms related to digital communication

i) Messages

ii) Characters

iii) Symbols

i) Messages

ii) Characters

iii) Symbols

6 M

2 (b)
Explain digital signal hierarchy using TI carrier system.

6 M

2 (c)
The output of an oscillator is described by x(t)=A cos(π Ft+θ) where the amplitude A is constant and F and φ are independent random
variables. The probability density function of θ is defined by [ f_\phi( heta) = \left{egin{matrix}
\frac {1}{2 \pi}, & 0 \le \theta \le 2\pi \0
& \text{otherwise}
\end{matrix} ight. ] Find the power spectral density of x(t) in terms of the probability density function of the frequency F.

8 M

Solve any one question from Q3 and Q4

3 (a)
Consider the signal S(t) shown in fig. Determine the impulse response of a filter matched to this signal and sketch it as a function of time, plot the matched filter output as a function of time.

8 M

3 (b)
Derive the expression of SNR for optimum filter.

8 M

Write a short note on:

4 (a) (i)
MAP

4 M

4 (a) (ii)
LRT

4 M

Draw & explain signal space representation of following signal.

4 (b) (i)
BPSK

4 M

4 (b) (ii)
8 Array PSK

4 M

Solve any one question from Q5 and Q6

5 (a)
Explain block diagrams for generation and reception of M-ary PSK signals. With suitable mathematical expressions, signal space representation Bandwidth and PSD.

10 M

5 (b)
Binary data is transmitted using PSK at a rate 3M bps over RF link having bandwidth 10MHz. Find signal power required at receiver input so that 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

6 (a)
Explain with block diagram QPSK receives Write an expression for its
error probability

8 M

6 (b)
find error probability of coherent FSK when amplitude of I/P at coherent optimal receiver is 10mv and frequency 1MHz, the signal corrupted with
white noise of PSD 10

^{-9}W/Hz. the data rate is 100kbps. [erfc (1.01) = 0.1531, erfc (1.11) = 0.1164, erfc (1.22) = 0.0844 & erfc (1.33 = 0.0599)].
10 M

Solve any one question from Q7 and Q8

7 (a)
Draw and explain 4bit P.N. sequence generator and find maximum length sequence.

8 M

7 (b)
The signal has the following parameter number of bits per MFSK symbol K = 2 number of MFSK tone M = 2

^{k}= 4 length of PN sequence per hop K = 3 total No. frequency hops 2^{k}= 8 sketch the o/p transmits freq of fast FH/MFSK signals.
8 M

8 (a)
Write a short note on personal communication system (PCS).

8 M

8 (b)
Compare DSSS with FHSS system.

8 M

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