Synthesis of Acoustic-Wave Duplexer Without Lumped Elements Shunted to Output Ports

In this paper, a method is proposed to synthesize acoustic wave duplexers with asymmetric ladder-type channel filters. By relocating the finite transmission zeros based on the sensitivity matrix, all resonators satisfy the requirement of keff2 and no additional lumped elements are needed at the output ports for simple fabrication and integration. Our method is validated by the synthesis of a B2 duplexer prototype, where the Tx and Rx filters operate at 1.88 and 1.96 GHz both with the bandwidth of 60 MHz, respectively. The case of asymmetric filter topology without shunted elements at output ports shows almost the same frequency response as that of the case of symmetric topology with shunted elements.