Abstract: A method and system for predistorting a signal before transmission of the signal to compensate for nonlinearities introduced when the signal is transmitted to a receiver. A signal received on a first frequency is evaluated at a receiver to determine whether the received signal includes nonlinearities without comparing the received signal to the original signal or a pilot tone. The nonlinearity data that result from the evaluation are transmitted back to the originator of the signal on a second frequency where the nonlinearity data are used to predistort signals before transmission therefrom. Communication of the nonlinearity data between transmitter and receiver at each site is through a reverse channel which is further controlled by a serial line.

Abstract: A device and method for correcting an amplitude slope in the frequency domain of an input signal. An amplitude slope is detected in parallel feedback loops that connect the combined output of two parallel out-of-band notch filters through a slope detection circuit to inputs of each of the two notch filters. Each feedback loop detects the energy at one of the high and low frequencies that define the frequency domain of the input signal, and provides a voltage indicative of the energy back to the notch filters to vary the Q of the notch filters, thereby correcting the amplitude slope. The energy is detected in each feedback loop by mixing the input signal with one of the high and low frequencies that define the frequency domain of the input signal, and filtering out all but the DC voltage indicative of the energy at the one frequency. The DC voltage changes the resistance of an element in the notch filters to vary Q.