Compact QMSIW Diplexer with High Isolation.

A novel substrate integrated waveguide (SIW) planar diplexer with very high isolation is presented. It is formed by two quarter mode substrate integrated waveguide (QMSIW) cavity resonators which are designed individually and combined through a T-junction. The diplexer channels are 13% and 15% relative bandwidths at 2.35GHz and 3.5GHz, respectively. Within the passband, the return losses are better than 22 dB and 25 dB with the insertion losses of 0.8 dB and 0.5 dB, in the lower and higher channels. Meanwhile, the diplexer exhibits a better than 42 dB isolation, indicating high isolation between the two channels. The measured results of the fabricated diplexer agree well with the simulated ones. [ABSTRACT FROM AUTHOR]