Pulse or digital communications – Repeaters – Testing
Patent
1992-07-07
1994-07-05
Chin, Stephen
Pulse or digital communications
Repeaters
Testing
375 99, H03H 730, H03D 104
Patent
active
053274601
ABSTRACT:
A method and apparatus for compensating for post-decision feedback equalization noise during decision feedback equalization. The method includes the steps of performing decision feedback equalization on a noisy signal, while isolating noise components of the noisy signal and filtering the isolated noise components to generate post-decision feedback equalization noise having desired spectrum and power. Preferably, the noisy signal is pre-filtered in a feedforward filter and the isolated noise components are filtered to compensate for noise enhancement that has resulted from filtration in the feedforward filter. The apparatus of the invention is a decision feedback equalizer including a quantizer and a noise filter circuitry for controlling the spectrum and power of the noise component of the signal received by the quantizer. The noise filter preferably has a transfer function B(z)/C(z), and the z-domain coefficients e'(z) of the noise received by the quantizer are e'(z)=[B(z)/C(z) ]e(z), where e(z) are the z-domain coefficients of the noise input to the noise filter circuitry. The noise filter circuitry preferably includes two filters whose transfer functions are B(z) and C(z), respectively, and the coefficients of B(z) and C(z) are selected to control the spectrum and power of the noise which interferes with the signal received by the quantizer. One class of embodiments employs a dummy quantizer to isolate the input noise received by a first filter of the noise filter circuitry.
REFERENCES:
patent: 4583234 (1986-04-01), Ramadan
patent: 4856031 (1989-08-01), Goldstein
patent: 4972433 (1990-11-01), Yamaguchi et al.
patent: 5008903 (1991-04-01), Betts et al.
IEEE Communications Magazine, Shahid Qureshi, Mar. 1982 on p. 13, FIG. 12.
Chin Stephen
Kim Kevin Y.
National Semiconductor Corporation
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