(EC 301) 5th Sem. May 2007
ANALOG COMMUNICATION SYSTEMS/ SYSTEM ANALYSIS & DESIGN
Instructions to Candidates:
(1) Section A is compulsory.
(2) Attempt any Four questions from Section B
(3)Attempt any Two questions from Section C
Section A
( 10 x 2 =20)
1.
(a) Explain the need of modulation?
(b) A single tone modulating signal f(f) = Em cos wmt; frequency modulates a carrier A cos wct. Find the frequency deviation.
(c) Explain capture effect and threshold effect in FM.
(d) Compare FM and AM from the noise performance point of view.
(e) What is a limited and why is it used.
(f) What are the advantages of obtaining AM by method of power conversion?
(g) Explain how PAM signals are defected using holding circuit.
(h) Show that coherent FSK is 3 db inferior to coherent PKS system.
(i) Draw the wave forms for PSK modulated signal for the binary signal 1010.
(j) What are the advantages of pulse modulation over continuous wave modulation?
Section B
( 4 x 5 =20)
2. Explain with necessary equations and a neat block diagram, the coherent detection of SSB signals.
3. The modulating signal, m(t) = 5 cos p t frequency modulates a carrier, c(t) = 10 cos 108t using a modulator of frequency sensitivity, 10 kHz/ volt. Find the modulation index and approximate bandwidth of the FM signal.
4. Derive the time domain expression of a single tone frequency modulated signal.
5. State and prove sampling theorem for low pass signals.
6. Draw and explain PWM modulator and demodulator circuit.
Section C
( 2 x 10 =20)
7. A narrow band FM has no amplitude variation, inspite of the fact that it has the same frequency components as AM. Justify the statement with phasor diagram.
8. A single tone modulating signal Em cos wmt frequency modulates a carrier A cos wcr. Show that:
(a) The detector output signal to noise ratio is proportional to the square of bandwidth of fM signal.
(b) The figure of merit is given by fm=(3/2) m2f.
9. Write notes on the following:
(a) Single side band BFO receivers
(b) AM detector with AGC
(c) Flat-top PAM.
ANALOG COMMUNICATION SYSTEMS/ SYSTEM ANALYSIS & DESIGN
Instructions to Candidates:
(1) Section A is compulsory.
(2) Attempt any Four questions from Section B
(3)Attempt any Two questions from Section C
Section A
( 10 x 2 =20)
1.
(a) Explain the need of modulation?
(b) A single tone modulating signal f(f) = Em cos wmt; frequency modulates a carrier A cos wct. Find the frequency deviation.
(c) Explain capture effect and threshold effect in FM.
(d) Compare FM and AM from the noise performance point of view.
(e) What is a limited and why is it used.
(f) What are the advantages of obtaining AM by method of power conversion?
(g) Explain how PAM signals are defected using holding circuit.
(h) Show that coherent FSK is 3 db inferior to coherent PKS system.
(i) Draw the wave forms for PSK modulated signal for the binary signal 1010.
(j) What are the advantages of pulse modulation over continuous wave modulation?
Section B
( 4 x 5 =20)
2. Explain with necessary equations and a neat block diagram, the coherent detection of SSB signals.
3. The modulating signal, m(t) = 5 cos p t frequency modulates a carrier, c(t) = 10 cos 108t using a modulator of frequency sensitivity, 10 kHz/ volt. Find the modulation index and approximate bandwidth of the FM signal.
4. Derive the time domain expression of a single tone frequency modulated signal.
5. State and prove sampling theorem for low pass signals.
6. Draw and explain PWM modulator and demodulator circuit.
Section C
( 2 x 10 =20)
7. A narrow band FM has no amplitude variation, inspite of the fact that it has the same frequency components as AM. Justify the statement with phasor diagram.
8. A single tone modulating signal Em cos wmt frequency modulates a carrier A cos wcr. Show that:
(a) The detector output signal to noise ratio is proportional to the square of bandwidth of fM signal.
(b) The figure of merit is given by fm=(3/2) m2f.
9. Write notes on the following:
(a) Single side band BFO receivers
(b) AM detector with AGC
(c) Flat-top PAM.