Abstract: There is disclosed a phase adjusted feedforward error correction system with improved linearity and bandwidth for use in high frequency systems. The feedforward system includes phase and amplitude equalizer circuits which cause a main amplifier output signal to be equal in amplitude and phase with the input signal and a second phase and amplitude equalizer circuit which causes the distortion products generated by the main amplifier to be equal in amplitude and phase with the distortion products from the main amplifier output before subtracting the distortion products from the main amplifier output signal. The phase and amplitude equalizer circuits simplify the construction of the feedforward circuit while maintaining inherent stability over the bandwidth and frequency of operation.

Abstract: An improved phase shift network is disclosed which is applicable to broadband systems, particularly in connection with feedforward power amplifier systems. The phase shift network includes a splitter for receiving an input signal and providing outputs which are coupled through all pass networks to produce signals differing in phase by a predetermined angle. The signals from the all pass networks are coupled through variable attenuators having their outputs recombined in a combiner to produce an output representing the input signal phase shifted by a predetermined angle. The phase shift may be adjusted by changing only one variable attenuator at a time to produce phase shifts of 90.degree. or greater.

Abstract: There is disclosed a feedforward system which reduces the phase and amplitude equalizer circuits necessary to provide for circuit operation. The main and error amplifiers of a phase adjusted feedforward system are constructed to have essentially equivalent delay and gain characteristics. The two loops formed by the main and error amplifiers are then phase and amplitude equalized by use of one phase/amplitude equalizer in the small signal loop between the output coupler and the hybrid junction. The circuit may be implemented with less complex structure, thereby resulting in additional circuit simplification and less cost.