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2. 发明专利

CA1150783A PROGRAMMABLE MULTIFREQUENCY TONE RECEIVER 未知
公开(公告)号：CA1150783A
公开(公告)日：1983-07-26
申请号：CA365623
申请日：1980-11-27
申请人： MOTOROLA INC
发明人： CONGER DAVID R L , GERSON IRA A , WHITE RICHARD E
IPC分类号： H04L27/30 , H04Q1/457 , H03H17/02 , G06F15/31
摘要： A multifrequency tone receiver is disclosed for detecting simultaneous tone signals in a sampled digital signal. The tone receiver includes a microprogrammed sequence controller, a time-multiplexed digital filter and a signal processing microcomputer. For each sample of the digital signal, the sequence controller is programmed to time multiplex the digital filter for performing three cascaded second order filtering operations (two bandpass filter operations and one low pass filter operation) for each of six tone signals to provide correspond ing energy estimates and one additional filtering operation to provide a total energy estimate. The signal processing microcomputer processes a number of sets of the seven energy estimates and provides an indication when a multifrequency tone pair has been detected. The digital filter, when enabled by a filter start signal from the sequence controller, asynchronously performs a single multiplication like filtering operation to implement each second-order filter, and provides a filter done signal upon completion of the filtering operation. Full-wave rectifying capability is provided during low pass filtering operations by logically complementing the digital filter input signal. Limit cycles may be suppressed in the digital filter output signal by rounding the output signal and clamping positive and negative overflows to the largest allowable positive and negative signals, respectively. The tone receiver may be advantageously utilized in a PCM communication system for detecting multifrequency tone signalling used for dialing and supervisory control. Moreover, the inventive tone receiver may be adapted to receive many different types of tone signalling simply by changing firmware therewithin,

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