| 摘要 |
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 paths with primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path. A distortion generator in the secondary path generates intermodulation signals, the amplitude of which is adjusted to match the amplitude of the distortion of the nonlinear device. A tilt adjustment is made to compensate the amplitude of the predistortion for frequency dependence of the amplitude of the distortion. A adjustment of the predistortion signal is also included so that phase of the distortion signal generated is in proper phase relation with the distortion inherent in the nonlinear device. A push-push amplifier is used as a distortion generator, with bias current unbalanced to produce net odd order intermodulation products as well as even order intermodulation products of the fundamental frequencies. |
