Pulse or digital communications – Repeaters – Testing
Patent
1993-04-09
1994-09-06
Chin, Stephen
Pulse or digital communications
Repeaters
Testing
375 99, 3647242, 333 18, H03H 730, H03H 740, H03K 5159
Patent
active
053454766
ABSTRACT:
An adaptive feedforward equalizer (12) has switched (N-1) tap-gain coefficients and a fixed tap-gain coefficient for the reference delay-line tap to operate on an incoming IF or baseband signal according to a first error signal (.epsilon..sub.1) representative of the difference between the input and output of a decision circuit (15). All tap-gain coefficients are active in the absence of an interference from an undesired source to cancel precursor distortion. The (N-1) tap-gain coefficients are nullified when such an interference is detected to reduce its precursor-cancelling capability. A first feedback equalizer (17) operates on the output of the decision circuit according to the first error signal to cancel postcursor distortion. A second feedback equalizer (18) nonlinearly filters the output of the decision circuit according to a second error signal (.epsilon..sub.2) and generates an estimate of a desired component of the output of the feedforward equalizer. The outputs of the second feedback equalizer (18) and the feedforward equalizer (12) are combined to produce the second error signal, or an estimate of an undesired component of the output of the feedforward equalizer. In the presence of the interference, the desired component estimate (.epsilon..sub.2) is combined with the outputs of the feedforward equalizer (12) and the first feedback equalizer (17) to produce an equalized signal for coupling to the decision circuit.
REFERENCES:
patent: 4870657 (1989-09-01), Bergmans et al.
patent: 4905254 (1990-02-01), Bergmans
patent: 4953183 (1990-08-01), Bergmans et al.
Ichiro Tsujimoto, "A New decision Feedback Equalization Method For Digital Radio," C&C Systems Research Laboratories, NEC Corporation 1990.
Chin Stephen
NEC Corporation
Webster Bryan
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