Novel RF interference rejection technique using a four-port diplexer

Abstract

Abstract-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 180 o and 183 o 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.

Four-Port Dual-Mode Diplexer with High Signal Isolation

“…As a result of a very complicated filter design and fabrication process, the insertion loss of the filter and diplexer can increase. Moreover, an alternative technique to design diplexer with low cost, high signal isolation, and ease of fabrication process was introduced by using four-port network [12,13]. e realized microstrip filter prototype with small circuit size can be achieved by this technique.…”

High isolation 4‐port diplexer based on double‐sided parallel‐strip lines

“…To protect the receiver from the leakage of high power transmitter and reduce the channel interference, the diplexer is often required to have a high isolation between the Tx and Rx ports. A lot of efforts have been made on increasing the isolation in diplexers . The common approach is to combine the bandpass filters (BPFs) through a 3‐port impedance matching network, usually in the form of transmission‐line based junctions that occupy a considerable footprint .…”

“…Recently a 4‐port diplexer architecture was proposed by I. Hunter . Its potential capability of interference rejection by over 60 dB was shown in network and circuit analysis.…”

“…A lot of efforts have been made on increasing the isolation in diplexers. [3][4][5][6][7][8][9] The common approach is to combine the bandpass filters (BPFs) through a 3-port impedance matching network, usually in the form of transmission-line based junctions that occupy a considerable footprint. 3,4 An alternative approach is to employ common resonators to replace the matching networks but with limited effect on the isolation enhancement.…”

“…Hunter. 9 Its potential capability of interference rejection by over 60 dB was shown in network and circuit analysis. No experimental verification has been reported so far.…”