| 摘要 |
An adaptive feedback system provides a means and method for removing selected signals from the feedback path, for compensating for changes in electrical characteristics of the feed forward and feedback paths so as to maintain negative feedback, and for prevention of closed-loop oscillation. Application to the suppression of amplifier distortion is emphasized. Cancellation techniques are employed to remove the desired output signal from the feedback path leaving only distortion to be negatively fed back. By this means, in-band distortion such as intermodulation products and noise can be suppressed without reduction in effective amplifier gain. Adaptive feedback compensation is used to assure negative feedback of a selected spectral band even when transfer characteristics of the forward and/or feedback paths vary due to such factors as changing input-signal parameters, component value drift due to environmental conditions, etc. Adaptive feedback compensation is achieved by either insertion and subsequent cancellation of a reference signal in the feedback path or by amplitude minimization of all fed back signals.
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