A miniaturized microstrip common resonator triplexer without extra matching network

A miniaturized microstrip triplexer with a common resonator has been proposed in this paper. By exploiting the variable frequency response of stepped-impedance resonator, the common resonator can be shared by three filter channels of a triplexer if its fundamental and higher-order spurious resonant frequencies are properly assigned. The proposed triplexer with a third-order Chebyshev frequency response at each channel is composed of only seven resonators. Moreover, extra matching network placed on the input port is needed for the conventional triplexer, but it is not needed for the proposed one. Experimental triplexer is fabricated and measured to verify the usefulness of the proposed concept. The measured results are in a good agreement with the simulated predictions. The size of the triplexer is only approximately 0.48 lambda_g x 0.32 lambda_g, showing a very small size.