A method of interference cancellation in binary PSK coherent receiver

Abstract

AbstractThe wide application of digital radio communication systems in recent years has resulted in increasing demands for allocated frequencies and, due to the overcrowded spectrum, interference has become a crucial problem. In many cases, such interference appears in the upper sideband or in the lower sideband of the useful signal. In the present paper a binary PSK communication system with interference in either the upper or the lower sideband is considered and a method of interference cancellation is proposed for the Costas loop widely used in PSK receivers. Experiments are conducted to demonstrate the efficiency of this method. The results show that the maximum cancellation with a simple circuit added to the Costas loop is 23 dB if Af (the difference between the frequencies of the PSK carrier and the interfering signal) is above 0.3 fβ (fβ the data bit rate). At the same time, the bit error rate in the digital signal is greatly improved. Also, with respect to the impairment due to jitter caused by interference, the performance of the Costas loop is practically unchanged within the specification range of an ordinary Costas loop. The advantages of the present method are that the circuit is simple, it is stable because there is no feedback in the interference cancellation part and the cancellation is effective even for interfering signals of unknown δf.