Feedbackward distortion compensating circuit

Claim 2

A distortion compensating circuit for a signal path subject to distortion comprising: means, connected to the output of said compensating circuit, for extracting a portion of the signal in said signal path; means, operating on said extracted signal portion, for producing a third order output signal therefrom; means for adjustably controlling the phase and amplitude of said third order output signal to provide a compensating signal having an opposing phase relationship with and an amplitude substantially equal to third order distortion effects present in said signal path; and means, connected to the input of said compensating circuit, for coupling the compensating signal to said signal path to substantially eliminate said third order distortion effects from said signal path.

Claim 3

The distortion compensating circuit, according to claim 1 wherein said third order signal producing means comprises: a squaring circuit for operating on a portion of the extracted signal thereby to produce a second order output signal; a multiplier circuit connected to receive said second order output signal and a portion of the extracted signal for multiplying the same thereby to produce a third order output signal.

Claim 4

The distortion compensating circuit according to claim 1 wherein the extracting means comprises a resolver for providing a determined phase shift between the signal in said signal path and the signal energy extracted therefrom, said phase shift being substantially constant over the frequency band and dynamic range of the signal in said signal path.

Claim 5

The distortion compensating circuit according to claim 1 further including means for eliminating feed-through signal components from the compensation signal which is coupled back into said signal path.

Claim 6

The distortion compensating circuit according to claim 1 further comprising: first means for equally dividing the second order output signal into first and second components shifted 180° from each other; second means for equally dividing a portion of the extracted signal into first and second components shifted 180° from each other; a first multiplier connected to receive the first components from the first and second dividing means; a second multiplier connected to receive the second components from the first and second dividing means, said first and second multipliers providing third order output signals by multiplying their respective input signals together; and signal combining means for adding the third order output signals from said first and second multipliers in phase to produce a single third order output signal, said signal combining means serving to eliminate those unwanted portions of the multiplier input signals that feed through to the outputs of said first and second multipliers.

Claim 7

A distortion compensating circuit for a signal path subjecting a transmission signal to distortion comprising: means, connected to the output of said compensating circuit, for extracting a part of the transmission signal in said signal path thereby to supply first and second portions of the same; a squaring circuit for operating on said first portion of the extracted transmission signal to produce a second order output signal; a filter connected to receive said second order output signal, said filter passing the second order harmonic frequencies of said transmission signal while blocking the fundamental frequency components of said transmission signal; means for introducing a propagation delay into said second portion of the extracted transmission signal; a multiplier connected to receive the output of said filtering means and the delayed second portion of the extracted signal, said multiplier multiplying together the signals applied thereto, thereby to produce a third order output signal; means for adjustably controlling the phase and amplitude of said third order output signal to provide a compensating signal having an opposing phase relationship with and an amplitude substantially equal to the third order distortion effects introduced to said transmission signal by said signal path; and means, connected to the input of said compensating circuit, for coupling the compensating signal to said signal path to substantially eliminate said third order distortion effects introduced by said signal path to produce an output transmission signal virtually free of same.

Claim 8

A distortion compensating circuit for a signal path subjecting a transmission signal to distortion comprising: means, connected to the output of said compensating circuit, for extracting a part of the transmission signal in said signal path thereby to supply first and second portions of the same; a squaring circuit for operating on said first portion of the extracted transmission signal to produce a second order output signal; a filter connected to receive said second order output signal, said filter passing the second order harmonic frequencies of said transmission signal while blocking the fundamental frequency components of said transmission signal; means for introducing a propagation delay into said second portion of the extracted transmission signal; a multiplier connected to receive the output of said filtering means and the delayed second portion of the extracted signal, said multiplier multiplying together the signals applied thereto, thereby to produce a third order output signal; means for adjustably controlling the phase and amplitude of said third order output signal to provide a compensating signal having an opposing phase relationship with and an amplitude substantially equal to the third order distortion effects introduced to said transmission signal by said signal path; and means, connected to the input of said compensating circuit, for coupling the compensating signal to said signal path to substantially eliminate said third order distortion effects introduced by said signal path to produce an output transmission signal virtually free of same.