Quadrature amplitude modulator using switched capacitor filter

Details Quadrature amplitude modulator using switched capacitor filter Quadrature amplitude modulator using switched capacitor filter

1987-05-01

1988-10-11

Grimm, Siegfried H.

Modulators

Amplitude modulator

Nonlinear device controlled by modulating signal

332 17, 332 21, H04L 2704

Patent

active

047774533

ABSTRACT:
A switched capacitor circuit implements a base band, finite impulse response filter (BBF) and balanced modulator with a single operational amplifier. The analog modulator has particular application in voice band modem applications and requires little or no microprocessor code space. Simplified sine and cosine functions are implemented in a pair of base band filters such that the output of only one base band filter is required at any one time. In this manner, a single operational amplifier may be utilized to implement the analog modulator/base band filter of the present invention. The use of switched capacitor technology and a single operational amplifier results in less silicon area dedicated to the analog modulator than for corresponding digital modulators.

REFERENCES:
patent: 4458216 (1984-07-01), Bingham
patent: 4626803 (1986-12-01), Holm
patent: 4661948 (1987-04-01), Shapiro et al.
patent: 4680556 (1987-07-01), Nakamura et al.

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