Digitally compensated direct conversion receiver

Details Digitally compensated direct conversion receiver Digitally compensated direct conversion receiver

1994-12-28

1996-11-26

Chin, Stephen

Pulse or digital communications

Receivers

Interference or noise reduction

455296, 455324, H03D 122, H04B 112, H04B 130

Patent

active

055793479

ABSTRACT:
A digitally compensated direct-conversion receiver includes devices for generating digital samples of a base-band in-phase signal and a base-band quadrature signal and for detecting the presence of a second-order product signal produced by an amplitude-modulated interfering signal. Also, the apparatus comprises a device for digitally compensating the digital samples by removing the second-order product signal, thereby producing compensated digital samples. In one method of digitally compensating samples of an information signal quadrature-modulating a carrier signal, estimated samples of a second-order product from a switched carrier signal are formed by averaging the digital samples during two time periods and by determining a time of ramps in the in-phase and quadrature signals that occur between the time periods due to the interfering signal. The digital samples may be differentiated and the results smoothed in determining the time of the ramps. In another apparatus, the estimated samples of the second-order product signal are produced by a device for averaging a square of a difference between respective digital samples of the in-phase signal and the quadrature signal, thereby determining an amplitude of the amplitude-modulated carrier signal, and a device for combining the amplitude and the digital samples, thereby generating the estimated samples.

REFERENCES:
patent: 4163940 (1979-08-01), Brewerton
patent: 4416017 (1983-11-01), Jasper et al.
patent: 4583239 (1986-04-01), Vance
patent: 4736455 (1988-04-01), Matsue et al.
patent: 4970469 (1990-11-01), Kasperkovitz
patent: 5241702 (1993-08-01), Dent
patent: 5422889 (1995-06-01), Sevenhans et al.

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