Dual band Substrate Integrated Waveguide (SIW) Filter With High Rejection and Selectivity

In this paper, a dual band bandpass filter with improved rejection between the two passbands and selectivity, is presented. The two passbands are centered at 2.4 GHz and 3.5 GHz with Fractional Bandwidths (FBW) of 4% and 5.5% respectively. Trisection topology is used to create both the passbands using rectangular SIW resonators resonating at its fundamental TE110 and next higher order TE210 modes. To reduce the circuit foot print, two layer structure is adopted. This design offers two transmission zeroes (TZs) in between the passbands resulting at least 48 dB rejection over 2.75 GHz-3.25 GHz. The measured reflection and transmission losses are better than 11.2 dB and 3.21 dB for first whereas they are better than 15.5 dB and 3.01 dB for the second passband respectively.