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Transmission of Compressed Analog Samples

IP.com Disclosure Number: IPCOM000046856D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Zuercher, M: AUTHOR

Abstract

Signals from a number of low-frequency signal sources SS1 to SSn are sampled by pulses SP having a frequency of, for example, 8 kHz. The analog samples are shifted into a number of analog shift registers ASR1 to ASRn. When a shift register is full, its contents are shifted out between two consecutive sampling pulses. The outputs of all shift registers are connected to a time multiplex bus from where the analog samples reach a transmission path TP through a low-pass filter LPF. Before transmission, the compression frequency n x 8 kHz has to be suppressed by suitable filters. At the receiver end, a similar arrangement with the same number of shift registers is used to expand and demultiplex analog samples.

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Transmission of Compressed Analog Samples

Signals from a number of low-frequency signal sources SS1 to SSn are sampled by pulses SP having a frequency of, for example, 8 kHz. The analog samples are shifted into a number of analog shift registers ASR1 to ASRn. When a shift register is full, its contents are shifted out between two consecutive sampling pulses. The outputs of all shift registers are connected to a time multiplex bus from where the analog samples reach a transmission path TP through a low-pass filter LPF. Before transmission, the compression frequency n x 8 kHz has to be suppressed by suitable filters. At the receiver end, a similar arrangement with the same number of shift registers is used to expand and demultiplex analog samples. Compared with conventional methods of time multiplexing the signal sources one after the other onto a bus, the new method requires a smaller frequency bandwidth for the transmission path. This reduction in bandwidth is obtained by groups of samples, rather than isolated single samples, being put onto the bus. As a result, the shape of the signal to be transmitted is much smoother than with conventional time multiplexing. With fewer amplitude jumps of the transmitted signal, a smaller frequency bandwidth is needed. Such amplitude jumps, occurring when an analog shift register currently being emptied is changed, may lead to a distortion of the signal to be transmitted.

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