Saturday, 28 December 2013


1.      A PLL can be used to demodulate FM signals.
2.      A PAM signal can be detected by using an integrator.
3.      The image channel rejection in a super heterodyne receiver comes from detector, RF and IF stages.
4.      SSB  analog modulation scheme requires the minimum transmitted power and minimum channel bandwidth.
5.      In a super heterodyne AM receiver, the image channel selectivity is determined by the pre selector and RF stages.
6.      A Hilbert transformer is a time varying system.
7.      Te maximum power efficiency of an AM modulator is 50%.
8.      For a message signal m(t)=cos(2π t) and carrier of frequency , cos[2π( + )t] represents  a single side band signal.
9.      The DSB-SC scheme has signal to noise ratio is 2.
10.  Ring modulator behaves like linear time variant circuit.
11.  AM SSB-SC wave form in time domain can be described by using Hilbert transform.
12.  Increases gain, Isolate LO, Increase selectivity are the functions of RF amplifier.
13.  Linear modulation is used in AM DSB-SC.
14.  Del square/12 general formula for normalized noise power.
15.  What is synchronous detection?
Ans: The local carrier generated at the receiver is phase locked with carrier at transmitter is called synchronous detection or coherent detection.
16.  Define coupling efficiency?

Ans: Ratio of power coupled into fibre to the power emitted from source n=pf/ps.


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