Design and Software Implementation of Analog and Digital Filters For Coherent Receivers under Noisy Channels

Abstract

Abstract One of the most important stations in any communications system is the filtering station. Due to the noise power that effects on the signal, the system must include filtering process to eliminate this effect. In this paper, analog and digital filters are designed and implemented using Matlab tools to solve the problems occurred during receiving the signal that effects on the synchronization such as those for coherent receivers. The offsets of Phase and frequency are major problems in the identification of signals that results reduction in the performance; such as, whenever higher order modulations are used. Two systems are designed and simulated. The first one is analog system and the second one is digital system. 3rd order Butterworth filter is selected for system one and digital IIR filter is selected for system two. Filter order was selected according to diagnosis the level of noise power and the transmitted frequency to meet certain frequency domain design specifications. Obtained results showed excellent performance in the receiving and demodulating the received signal. Evaluation of the results is basically depend on comparison between the transmitted and received samples.