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Pulse Amplitude Modulation and Pulse Code Modulation

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15 diapositives · 335 Views · Jan 04, 2020

Pulse Amplitude Modulation and Pulse Code Modulation. oleh Warsun Najib. t. 0. T. t. 0. t. 0. T. 0. t. t. 0. Pulse Amplitude Modulation. Low Pass. Band Pass. 0. 0. *make sure that Sinc function is big and flat by reduce time. By using very narrow. Demodulation of PAM. PAM1.

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Pulse Amplitude Modulation and Pulse Code Modulation
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  1. Pulse Amplitude Modulation andPulse Code Modulation oleh Warsun Najib

  2. t 0 T t 0 t 0 T 0 t t 0 Pulse Amplitude Modulation PAM-PCM

  3. Low Pass Band Pass 0 0 *make sure that Sinc function is big and flat by reduce time By using very narrow Demodulation of PAM PAM-PCM

  4. PAM1 LPF PAM-TDM before filtering Pulse generator PAM-TDM to the transmission line LPF switch Clock Pulse generator PAM2 LPF Sampler Sampler Switch : determining the synchronization and sequence of the channels Clock : determine the timing of the overall system Pulse generator : produces narrow rectangular pulses to drive the sampler Multiplexing PAM-TDM PAM-PCM

  5. T Two signal are sampled equally Tx=the time interval between adjacent channels or samples Nyquist interval for one signal For n channel Nyquist Sampling PAM-PCM

  6. Tx Tx 0 -BF BF S1 S2 S3 S4 With condition of equal BW and sampling equally therefore the Total BW Requirement is n x BW If BW of each channel is not equal Therefore the Total BW Requirement is n x largest BW Bandwidth Requirement PAM-PCM

  7. Transmitting Analog signal in Digital format • Advantages • Immunity to noise : with some amount of noise digital can withstand while analog failed to provide virtually error free transmission. • Reduce signal to noise ratio • Error control coding ; parity check, Hamming code make more reliable • Signal can be completely regenerated at intermediate regenerator for long haul system. • More compatible with computer system for signal processing and digital memories for data storage. • More elaborate code can be used. • Ideal for integrated services digital network (ISDN) PAM-PCM

  8. Pulse Code Modulation • m(t) is sampled, each sample value is rounded off to the nearest allowable value. This value is digitally encoded as a sequence of binary digits • There are three process of Digitization 1. Sampling 2. Quantization (devide into level of voltage) The approximation of amplitude value of sinal m(t) into one of M discrete quantized values 3. Encoding Each quantization level is encoded into N binary digits Where N is the number of binary digit per code word M is the number of quantization level PAM-PCM

  9. Where M = no. of steps = quantization step V 0 M Steps -V t Sampling Signal Quantization PAM-PCM

  10. V 111 110 101 100 0 011 010 001 000 -V 1 1 1 1 1 0 1 0 0 0 1 1 0 1 0 1 0 0 1 0 1 1 1 t Encoding PAM-PCM

  11. Quantization Noise 0 Quantization Error Uniform distribution PAM-PCM

  12. time Signal to Noise Ratio The average power Time average Continuous RV PAM-PCM

  13. where Signal to Noise Ratio[1] PAM-PCM

  14. In dB Encoding : each quantization level is encoded into N binary digit No.of level No.of binary digit per code word Signal to Noise Ratio[2] PAM-PCM

  15. MAN WOMAN voice time 0 300 500 800 3.4k 3.1k Nyquist 300 3.4k (2x3.4k=6.8k) Each sample is quantized and encoded into 8 bits Bit rate = x 8 = 64kbps ; with 32 channels 1channel = 8 bits therefore 8 x 488.25nsec = 3.9 sec Total bit length = 8 bit x 32 channels = 256 bits TDM-PCM (E1 standard) PAM-PCM