Abstract: In a feedforward amplifier for amplifying an input signal in order to produce an amplified output signal, an error signal representative of distortion in the amplified output signal is produced and an adaptive linearization circuit is provided. In this adaptive linearization circuit, serially interconnected attenuator, phase shifter and error amplifier process the error signal to produce a feature-adjusted error signal. A coupling member combines the feature-adjusted error signal in the amplified output signal in order to cancel distortion in this amplified output signal, and a comparator/controller circuit is responsive to the error signal and the feature-adjusted error signal to control the attenuator and the phase shifter.

Abstract: A linearizer channel amplifier for use in conjunction with a power amplifier comprises an input series circuit formed of a first variable attenuator, an input drive amplifier and a power limiter, and an output series circuit formed of a second variable attenuator and an output drive amplifier. Between the input and output series circuits is interposed a linearizer. In this linearizer, a splitter produces first and second signal portions, a first path comprises serially interconnected predistorter and third variable attenuator for distorting and adjusting the amplitude of the first signal portion, a second path comprises serially interconnected phase shifter and fourth variable attenuator for phase-shifting and adjusting the amplitude of the second signal portion, and a combiner combines the distorted and amplitude-adjusted first signal portion and the phase-shifted and amplitude-adjusted second signal portion to form a predistorted output signal applied to the output series circuit.

Abstract: In an adaptive method and device for predistorting a signal to be transmitted, supplied by a signal source to an input of a power amplifier having a output for delivering an amplified output signal, the following steps are conducted: predistorting the signal to be transmitted by means of cascaded predistortion amplitude and phase look-up tables interposed between the signal source and the input of the power amplifier, producing a first feedback signal in response to the predistorted signal, producing a second feedback signal in response to the amplified output signal from the power amplifier, delaying the first feedback signal for eliminating any time lag between the first and second feedback signals, and real time modeling the predistortion amplitude and phase look-up tables in response to the first and second feedback signals in order to update these two tables.