Predistorter for linearization of electronic and optical signals

Details Predistorter for linearization of electronic and optical signals Predistorter for linearization of electronic and optical signals

1991-02-08

1992-07-21

Mullins, James B.

Amplifiers

Hum or noise or distortion bucking introduced into signal...

328163, H03F 132

Patent

active

051326396

ABSTRACT:
An electronic circuit provides a linear output from an amplitude modulated transmission device such as a semiconductor laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two or three paths with primary part of the signal applied directly to the device, with a time delay to compensate for delays in two secondary paths. One secondary path generates even order intermodulation products and the other generates odd order intermodulation products. These are recombined with the primary signal in proper phase and amplitude for cancelling distortion in the output device. A distortion generator in each secondary path generates adjustable amplitude intermodulation signals. A tilt adjustment is made to compensate the amplitude of the predistortion for frequency dependence of the amplitude of the distortion. Phase of the distortion signal is adjusted to be in proper phase relation with the distortion of the device. In the even order path there are means for adjusting predistortion at an intermediate frequency so that the distortion is cancelled near the upper, lower and intermediate portions of the frequency range of the device.

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