Predistortion Technology Used for TWTA

According to the predistortion technique of travelling wave tube amplifiers (TWTAs), by analyzing TWTA model proposed by Saleh, the gain transmission function curve and phase expansion function curve of the predistortion circuit are deduced. The linear range of TWTA could be enlarged by using predistortion technique, and invariable gain together with zero phase excursions are reached at the working region of the linearized TWTA. As a kind of microwave and millimeter wave amplifiers, TWTAs find a wide utilization in communication, radar and electronic countermeasure applications. To obtain high output power, TWTAs are usually working at their saturation region where severe nonlinear distortion appears. The nonlinearity manifests gain compression and phase excursion. For digital communications application, the nonlinear distortion increase bit error rate, and this limits system efficiency. For electronic countermeasure applications, the nonlinear distortion limits the output power obtainable at the carrier frequency, and this limits the obtainable efficiency of the system. So insights into measures to improve nonlinearity of TWTAs will benefit wireless communications systems and electronic countermeasure systems. Predistortion technique is one of the best choices [1,2,.