SUMMARY ■          The use of digital communications offers several important advantages as compared to analog communications. ■          Digital communications have become the dominant form of communication technology in our society. ■          To handle the transmission of analog message signals (i.e., voice and video signals) by digital means, the signal has to undergo an analog-to-digital conversion…. Continue reading »

EXAMPLE 4.21. Consider an audio signal with spectral components limited to the frequency band of 300 to 3300 Hz. A PCM signal is generated with a sampling rate of 8000 samples/s. The required output signal-to-quantizing-noise ratio is 30 dB.             (i)         What is the minimum number of uniform quantizing levels needed, and what is the… Continue reading »

Advantages , DIFFERENTIAL PULSE CODE MODULATION (DPCM) :- ADAPTIVE DELTA MODULATION (i) Reason to use Adaptive Delta Modulation             To overcome the quantization errors due to slope overlod and granular noise, the step size (D) is made adaptive to variations in the input signal x(t). Particularly in the steep segment of the signal x(t), the… Continue reading »

Drawback of Conventional Delta Modulation , use of Integrator :- DELTA-SIGMA MODULATION   (U.P. Tech. Sera. Exam, 2004-05) (10 Marks) 4.29.1 Drawback of Conventional Delta Modulation             The quantizer input in the conventional delta modulator can be considered as an approximation to the derivative of the input message signal. Hence, the noise results in an… Continue reading »

ADVANTAGES of pulse code modulation ppt , DRAWBACKS OF PCM :- APPLICATIONS OF PCM Some of the applications of PCM may be listed as under: (i)         With the advent of fibre optic cables, PCM is used in telephony. (ii)        In space communication, space craft transmits signals to earth. Here, the transmitted power is quite small… Continue reading »

ROBUST QUANTIZATION: NECESSITY OF NONUNIFORM QUANTIZATION IN A PCM SYSTEM (U.P. Tech., Sem. Examination, 2003-2001) As discussed earlier, in uniform quantization, the quantizer has a linear characteristics. The step size also remains same throughout the range of quantizer. Therefore, over the complete range of inputs, the maximum quantization error also remains same. We know that… Continue reading »

EXAMPLE 4.5. Twenty four voice signals are sampled uniformly and then have to be time division multiplexed. The highest frequency component for each voice signal is equal to 3.4 kHz. Now             (i) If the signals are pulse amplitude modulated using Nyquist rate sampling, what would be the minimum channel bandwidth required.             (ii) If… Continue reading »