1.a. What is delta-sigma modulator? Draw its block diagram , what are its advantages?

1.b. What is time division multiplexing? Explain how allocation of time slots in TDM depens on bit-rate.

1.c. What is a strictly stationary process? Explain.

2.a. A binary channel with 36 kbps bit rate is available for PCM voice transmission, Find

i) Number of quantization levels.

ii) Number of bits per sample

ii) Sampling frequency

The voice signal is band limited to 3.4 KHz

2.b. What is synchronization ? Explain any one bit synchroniser.

2.c. If a while Gaussian noise is passed throgh a ideal low pass filter. Find the autocorrelation function of the filtered noise. Assume passband amplitude response of filter H(f) = 1 and cutoff frequency W Hz,

3.a. Explain likelihood ratio test. (LRT)

3.b. A received binary signal has amplitude $\pm 2V$ and bit duration is $T_{b}$. The signal is corrupted by AWGN having power spectral density $10^{-4} volt^{2} / Hz$ . If the signal is processed by integrate and dump filter, what will be required value of $T_{b}$ so that error probability is less than or equal to $10^{-4}$. Given Q (3.71) = $10^{-4}$

3.c. State any one property of matched filter.

4.a. Derive the expression for signal - to - noise ratio of integrate and dump filter

4.b. Find impulsive response of matched filter whose input is given by

4.c. Draw the block diagram of correlation receiver for binaty digital input signal

5.a. Explain the band-pass transmission model (Both transmitter and receiver)

5.b. Binary data is transmitted using PSK at a rate 2 Mbps over RF link having bandwidth 2 MHz , find signal power required at the receiver input so that error probability is not more than $10^{-4}$ . Given noise PSD $\dfrac{ N_{0}}{2} = 10^{-10}$ watt/Hz and Q (3.71) = $10^{-4}$ .

5.c. Explain QPSK signal generation.

6.a. Explain M-ary PSK transmitter and receiver

6.b. Binary data is transmitted using M-ary PSK at a rate 2 Mbps over RF link having bandwidth 2 MHz find signal required at the receiver input so that bit error probability is less than $10^{-5}$

Given M = 16 and Noise PSD $\dfrac{ N_{0}}{2} = 10^{-8}$ watt/Hz erf(3.1) = 0.99996

6.c. Explain coherent binary FSK signal generation.

7.a. Draw the block diagram of spread spectrum digital communication and explain the various blocks.

7.b. State and explain properties of PN sequence.

7.c. What are advantages of FHSS.

8.a. Draw the block diagram of FHSS transmitter and receiver and explain the various blocks.

8.b. The DSSS communication system has message bit duration $T_{b}$ = 4.095 ms and chip duration $(T_{c})$ = 1 $\small \mu$ sec. with $\dfrac{ E_{b}}{N_{0}} = 10$ for average error probability less than $10_{5}$. Calculate processing gain and Jamming margin.

8.c. What are disadvantages of DSSS.