Method and apparatus for eliminating DC offset for digital I/Q d

Details Method and apparatus for eliminating DC offset for digital I/Q d Method and apparatus for eliminating DC offset for digital I/Q d

1994-11-14

1996-08-20

Mis, David

Demodulators

Frequency modulation demodulator

Having specific distortion, noise or other interference...

329323, 329349, 329358, 375317, 455315, H03D 100, H03D 300, H03D 716, H04B 126

Patent

active

055482449

ABSTRACT:
A method and apparatus utilizing the techniques of frequency shifting and filtering for converting an input signal having a desired signal at intermediate frequency and an undesired DC offset to a baseband frequency signal in which the undesired DC offset is eliminated. The apparatus includes a first multiplier for multiplying the input signal by a signal having substantially the same intermediate frequency plus an offset frequency (.DELTA.f) to produce a first output signal wherein the desired signal is shifted in frequency to the offset frequency (.DELTA.f) and the undesired DC offset is unaffected. The apparatus also includes a second multiplier coupled to the first multiplier for multiplying the first output signal by a signal having substantially the same offset frequency (.DELTA.f) to produce a second output signal having the desired signal shifted to baseband frequency and the undesired DC offset shifted in frequency to the offset frequency .DELTA.f. In addition, a filter coupled to the second multiplier filters the output signal to remove the undesired DC offset while leaving the desired signal, now located at baseband frequency, intact.

REFERENCES:
patent: 3860874 (1975-01-01), Malone et al.
patent: 4438524 (1984-03-01), Muilwijk
patent: 4878029 (1989-10-01), Saulnier et al.
patent: 4888557 (1989-12-01), Puckette, IV et al.
patent: 5287067 (1994-02-01), Denno et al.

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