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

1992-07-21

1993-10-12

Mullins, James B.

Amplifiers

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

328163, H03F 132

Patent

active

052529304

ABSTRACT:
An electronic circuit provides a linear output from an amplitude modulated transmission device such as an amplifier or a semiconductor laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal with distortion equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two paths with the primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path. The secondary path generates predistortion which is recombined with the primary signal in proper phase and amplitude for cancelling distortion in the output device. A distortion generator in the secondary path generates adjustable amplitude intermodulation signals. Filtering is used before the distortion generator to compensate for the dependence of the distortion of the nonlinear device on the frequencies of the fundamental signals. Filtering is used after the distortion generator to compensate for the dependence of the distortion of the nonlinear device on the frequency of the distortion. Phase of the distortion signal is adjusted to be in proper phase relation with the distortion of the device. Set points of the predistorter may be adjusted automatically. More than one secondary path may be used.

REFERENCES:
patent: 3732502 (1973-05-01), Seidel
patent: 4068186 (1978-01-01), Sato
patent: 4392253 (1983-07-01), Yamada et al.
patent: 4992754 (1991-02-01), Blauvelt
patent: 5126687 (1992-06-01), Onoda et al.
Prochazka, et al., "Amplifier Linearization by Complementary Pre- or Post-Distortion", IEEE Transactions on Cable Television, vol. CATV-1, No. 1, Oct., 1974 pp. 31-39.
Asatani, et al., "Linearization of LED Nonlinearity by Predistortions", IEEE Transactions on Electron Devices, vol. ED-25, No. 2, Feb. 1978 pp. 207-212.
Childs, et al., "WH6 Predistortion linearization of directly modulated DFB Lasers and External Modulators for AM Video Transmission", OFC/Wednesday 24th,/79 2:30 P.M., one page.
Bertelsmeier, et al., "Linearization of Broadband Optical Transmission Systems by Adaptive Predistortion", Frequenz Band 38 (Sep. 1984) pp. 206-212 (plus one page).

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