New designs of bandpass diplexer and switchplexer based on parallel-coupled bandpass filters

In this paper, new designs of a bandpass diplexer and switchplexer are presented. Based on the proposed design method, they can be implemented by the direct connection of two parallel-coupled bandpass filters. As a result, the circuit size and mismatch losses can be reduced compared with conventional designs. In addition, based on the proposed filter prototypes, multiple functional blocks in the RF front end can be integrated into a single component. As an example, a balun-integrated bandpass switchplexer that effectively integrates all the functional blocks between the antenna and the TX/RX amplifiers in a single-band RF transceiver is demonstrated. In this way, not only can the level of integration of the RF front end be further improved, but the circuit size and power losses can also be reduced.