Predistortion circuit with feedback
 A predistortion circuit for a microwave power amplifier which exhibits phase and amplitude nonlinearities and has a small signal gain equal to a. The phase distortion circuit includes a 180.degree. coupler, a first coupler for coupling a given fraction of the input power to the 180.degree. coupler and a second coupler for coupling the given fraction of the power output from the amplifier, reduced by a, to the 180.degree. coupler. The 180.degree. coupler has a difference output port at which a signal appears which corresponds substantially to the difference in phase between the two signals input to the 180.degree. coupler and has a sum port at which a signal appears which corresponds substantially to the sum in amplitude between the two signals input thereto. A phase change circuit and attenuator are coupled between the first coupler and input to the power amplifier. Signals related to the signals produced at the difference port and sum port of the 180.degree. coupler are utilized to control the amount of phase change in the phase change circuit and the amount of attenuation in the attenuator circuit to thereby reduce the phase and amplitude nonlinearities of the signal produced by the power amplifier. 
RCA Corporation
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inventional inventional additional
James C. Mahesh
Whartenby Kumar