Diplexer with high isolation using multi-order resonances

Diplexer with high isolation was proposed in this paper. We analyze the design procedure of diplexer and then add three order resonances in diplexer. 0.25A transmitting lines at distinguished working center frequency are used to make the isolation between two paths of diplexer better. Test results show that diplexer with two bands at 1.95 GHz and 2.12 GHz is realized. Favorable out-of-band rejection can be seen in measurement, and the isolation between two paths is below -25 dB in the whole band 1.5 GHz to 2.5 GHz.