Review on technologies used to design RF diplexers

In recent years, the digital world has seen the advent of new mobile applications with bandwidthintensive activities. In fact, this phenomenal evolution of systems and applications dedicated to wireless communication has been a direct consequence of scientific and technical advances in this field. In this perspective, improving the use of these applications requires a great need for bandwidth. In order to optimize the use of bandwidth, multiservice and multistandards wireless communication systems represent an attractive solution. In fact, realizing a multiservice system requires the use of the duplexing function, which allows a transceiver to carry out a bidirectional communication. For this purpose, two duplexing procedures are commonly used: TDD (Time-Division Duplexing) and FDD (frequency-Division Duplexing). Transceivers that use FDD duplexing require simultaneous operation of the transmitter and receiver that share the same antenna. For that, two separate bandwidths are used for transmission and reception. Therefore, it is necessary to use a diplexer consisting of two very selective filters one centered on the transmission band and the other on the receive band to separate the transmission and reception signals. Due to the finite isolation of the diplexer, strong leakage of the transmission signal desensitizes the receiving path. Thus, the design of this type of circuit is not simple and it is necessary to achieve a diplexer with high isolation and low insertion loss to ensure proper functioning of the entire system.