Friday, 27 December 2013

DIGITAL COMMUNICATION


DIGITAL COMMUNICATION

1.      The amplitude of the pulse change according to amplitude of modulation signal at the sampling instant is called pulse amplitude modulation.
2.      Minimum transmission bandwidth of TDM channel =NW.
3.      The pulse code modulation technique sample the input signal x(t) at frequency =2W.
4.      Inherent errors are introduced in the signal. This error is called quantization error.
5.      Companding  will reduce the quantization error.
6.      The differential pulse code modulation (DPCM) works on the principle of prediction.
7.      PSK, FSK, ASK are the types of passband modulation.
8.      The BPSK signal can be generated by applying carrier signal to the balanced modulator.
9.      The analog signal is converted to digital or binary waveform by means of waveform coding techniques.
10.  Digital representation of the signal is a sequence of   Binary   numbers.
11.  Transmission of two or more bits simultaneously is known as  M-ary transmission.
12.  In QPSK   modulation,one of four possible waveform is transmitted during each interval T.
13.  Correlative filtering initially introduces controlled inter symbol interference.
14.  The function of optimum receiver is, minimization of    Probability error .
15.  MSK uses Two number of bits per symbol.

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