Satellite Transponder Performance Evaluation in the Presence of the linearizer base Circulator

In this paper, analysis of a linearized Travelling Wave Tube (TWT) under the digital modulation schemes is presented. The pre-distortion linearizer circuit based on the schottky diodes and circulator is used to compensate nonlinear behavior of the TWT amplifier in the noisy channel. The Quadrature Amplitude Modulation (QAM) is utilized and applied before linearized TWTA in order to capture results. The data passing through the linearized TWTA is analyzed by using Advanced Design System (ADS). Constellation and eye diagrams are obtained from a telecommunication link. In addition, Bit-Error-Rate (BER) performance of the system is evaluated using Monte Carlo estimation for three different values of Input-Back-Off (IBO). Finally, it is shown that the system performance is improved considerably by applying the proposed signal pre-distortion linearizer base circulator.