A system for stabilization of the coupling value between the transmitted radio signals resulting from cross polar discrimination, using the transmit power level control in radio link systems formed of several radio channels using multilevel QAM modulation. A first control signal is derived for each RF channel and a second control signal is derived for the adjacent channels. The first and second control signal are then combined to derive threshold signals. The threshold signals are multiplexed with station identification signals and this multiplexed signal is multiplexed with other service signals. The twice multiplexed signal is then inserted in the frame of a main information signal. The signal is demultiplexed to derive a remote transmit power control signal. The atmospheric precipitation condition is evaluated through statistical control of the bit error rate. A local transmit power level control signal is derived. The local and remote transmit power control signals are then applied the predistortion circuits of the power amplifiers.
Point-to-point microwave system is the backbone link for mobile communication. In tropical region, rain attenuation is the major constraint for implementing microwave system above 10 GHz. The extreme of propagation channel environment due to rain has brought to the research and development of adaptive transmit power control (ATPC) in microwave transceiver. ATPC varies the transmit power level in order to maintain the receive signal level (RSL) above the threshold for bit-error-rate (BER) desired. This paper discussed the design and performance analysis of ATPC in simulation and experimental. Simulation is performed for analyzing the effect of ATPC to the transceiver non-linearity performance. ATPC subsystem is developed and tested in an experimental link with real-time rain faded signal.