SIW Dual-Mode Dual-Band Balanced Filter With Closely Spaced Passbands

In this paper a substrate integrated waveguide (SIW) dual-mode dual-band (DMDB) balanced filter (BF) with closely spaced passbands has been proposed. The first differential-mode (DM) passband can be achieved by the TE
401
mode in SIW rectangular cavities (RCs) and the second can be obtained by the TE202 mode. The two bandwidths could be realized over a wide range of ratio by applying the design parameters ratio technique, the desired coupling coefficients of both passbands are achieved by properly setting positions and size of the coupling windows which are opened on the adjacent RCs with common post-wall. A third-order direct-coupled DMDB BF operates at 15.97GHz and 18.31GHz with respective fractional bandwidth (FBW) of 1.7% and 2.5%, and the center frequency ratio is approximately equal to 1.147. The simulation results show good performance of the DMDB BF.