10-401-05-FormattingQuantizePCM

10-401-05-FormattingQuantizePCM - Formatting Quantization...

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EE 401/522 Digital Communications Formatting Quantization Pulse Code Modulation (PCM) PCM transmission system PCM waveforms(line codes)
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Signal Design (PCM) 2 EE 401/522 Digital Communications FORMATTING AND BASEBAND MODULATION Format Pulse modulate Bandpass modulate Transmit Channel Receive Format Detect Demodulate / Sample Synchronization
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3 EE 401/522 Digital Communications Format and pulse(baseband) MODEM Sample Quantize Encode Pulse Modulate Analog Textual Digital Information Source Sampling Detection Decode Low-pass filter Digital Textual Analog Information Sink 010100 Channel
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Sampling Process 4 EE 401/522 Digital Communications Your comments on the product ?
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Intr. to Digital Communications 5 EE 401/522 Digital Communications Sampling process
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Intr. to Digital Communications 6 EE 401/522 Digital Communications Quantization
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Signal Design (PCM) 7 EE 401/522 Digital Communications Quantization process Uniform (or linear) quantizer 4T s 2T s 0 2T s 4T s x s t =x t x δ t t Sampled signal L-level q = : quantile interval L = 2 R R : the number of bits per sample
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Signal Design (PCM) 8 EE 401/522 Digital Communications Quantization error The approximation in the linear quantizer will produce an error e less than |q/2| volts. This error is assumed to be distributed uniformly , then, its pdf is p(e)=1/q A figure of merit for quantizer is the quantizer variance given by σ 2 = q / 2 q / 2 e 2 p e de= q / 2 q / 2 e 2 1 q de= q 2 12 The variance corresponds to the average quantization noise power The peak power of the analog signal can be expressed as V p 2 = V pp 2 2 = Lq 2 2 = L 2 q 2 4
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Signal Design (PCM) 9 EE 401/522 Digital Communications SNR for Quantization The ratio of peak signal power to average quantization noise power is S N q = L 2 q 2 / 4 q 2 / 12 = 3L 2 = 3 2 2R
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10 EE 401/522 Digital Communications Pulse Code Modulation (PCM) Class of baseband signals obtained from the quantized PAM signals by encoding each quantized sample into a digital word Perform L level quantization, obtain quantized samples Each sample is encoded digitally into l-bit codeword (l=log 2 L) For basebad transmission,each codeword is transformed to pulse
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This note was uploaded on 12/15/2010 for the course EE EE 401 taught by Professor Alikara during the Spring '10 term at Ankara Üniversitesi.

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10-401-05-FormattingQuantizePCM - Formatting Quantization...

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