Synthesis and design of microwave diplexers with a common resonator junction

A method for synthesizing microwave diplexers is presented. It is based on the evaluation of the characteristic polynomials of the TX and RX filters composing the diplexer with a common resonator junction. An objective error function can be constructed using the transmission and reflection zeros obtained from the polynomials of the TX and RX filters. The coupling matrix of the TX and RX filters (M_TX and M_RX) are synthesized independently by optimizing the objective error function. The coupling matrix of the diplexers can be obtained from M_TX, M_RX and the equivalent capacitance of the common resonator junction in the normalized frequency domain.