Kurukshetra University 2009 B.Tech Electronics and Communications Engineering K.UAnalog Communication E.C.E - Question Paper
PAPER Ist
UNIT - I
Q.1. (a) A receiver having overall gain A, output resistance RL & bandwidth B
operates at temperature T oK. The receiver input resistance is RT & it is fed from antenna having resistance Ra. Derive a formula for noise power No. Also find the value of the noise figure F in terms of Ra, RT & Req, where Req is the equivalent noise resistance excluding RT. (10)
Q.1. (b) The noise output of a resistor is amplified by a noiseless amplifier having gain
of 60 & bandwidth of 90 kHz. A meter connected to the output of the
amplifier reads 1.2mV rms. (i) if the resistor is operated at 17oC what is its
resistance? (ii) if the bandwidth of the amplifier is reduced to 10kHz, its gain
remaining constant. What will be meter read now? (10)
Q.2. (a) What are the various sources of noise? (5)
Q.2. (b) Define noise bandwidth. What is the relation between noise bandwidth BN &
noise power Po at the output of the system? (7)
Q.2. (c) Give the mathematical representation of noise. (8)
UNIT - II
Q.3. (a) Wlrat is moduiation ? Why is it required to modulate a signal before
transmission?
Q.3. (b) Find an expression for the instantaneous voltage of an amplitude modulated
signal. Draw the waveforms for amplitude modulated signal; also describe the
power relations involved in AM. (10)
Q.3. (c) Compare DSBSC-AM and SSB-AM. (5)
Q.4. (a) With the help of suitable diagrams and waveforms describe the square law
Diode modulation system. (10)
Q.4. (b) Explain the working of linear diode detector. (5)
Q.4. (c) The rms value of a carrier voltage after amplitude modulation to a depth of
40% by a sinusoidal moduiating voltage is 55 V. Calculate the rms value of
Carrier voltage when it is modulated to a depth of 80%. (5)
UNIT - III
Q.5. (a) In a FM system if mf is doubled by halving the modulating frequency, what
will be the effect on maximum deviation? (5)
Q.5. (b) Expiain the spectrum of a frequency modulated signal and compare it with that
of amplitude modulated signal. (15)
Q.6. (a) What is the principle of operation of slope detectors? Explain in detail the
Working of a balanced slope detector. (10)
Q..6. (b) What is pre-emphasis and why is it required? (5)
Q.6. (c) Differentiate between WBFM & NBFM. (5)
UNIT - IV
Q.7. (a) Draw and explain the complete block diagram of Armstrong
Frequency modulation system. In what circumstances can we dispense with the mixer ? (10)
Q.7. (b) Explain radio telephone transmitter highlighting its special features like
Compressors, VODAS & privacy devices. (10)
Q.8. (a) Explain with neat diagram the functioning of a TRF receiver. (10)
Q.8. (b) Discuss the working of delayed AGC as compared to simple AGC. Show the
curves to illustrate the comparison. (10)
| Earning: Approval pending. |
