Abstract: A method and apparatus for reducing the effects of dielectric absorption to a loop filter capacitor utilized in a dual-mode open-loop modulator having a transmit and receive communication frequency. The modulator incorporating a phase lock loop having means for maintaining a substantially constant voltage across the loop filter capacitor irrespective of the communication frequency implemented.

Abstract: The second-order predistorter comprises two RF amplifiers and three 180.degree. hybrid combiner/splitters. The RF sinusoidal input is split into two separate signals which have equal amplitudes but are 180.degree. out of phase. Each of these signals is fed into separate moderately linear amplifiers, the output of each being composed only of the amplified input signal and second-order distortion components produced by the amplifiers' nonlinearities. The output signal from each amplifier is combined with the other in a second combiner/splitter to produce two different outputs consisting of the sum and difference of the amplified signals. The difference signal consists only of the desired signal, and the sum signal consists of only the second-order distortion terms. The sum and difference signals are recombined in a third combiner/splitter to form a composite signal which is input into the device to be linearized.