Novel RF Interference Rejection Technique using a Four-port Diplexer

A novel RF interference rejection technique using four-port network is presented in this paper by using two diplexers combined together. This technique offers the signal isolation of 68.46 dB between transmitter and receiver module, which is the best figure ever reported. The four-port network exploits both high and low-Q factor filters for the cost reduction. The design tolerance with phase deviation between 180º and 183º of four-port network was investigated and the novel concept still has signal isolation (S32) of better than 65.47 dB, which is still superior compared to the existing diplexer. Finally, RF interference rejection technique can be used in wireless communication systems whereas small size, low losses and low complexity are required.