Development of Substrate Integrated Waveguide filters for low-cost high-density RF and microwave circuit integration: Pseudo-elliptic dual mode cavity band-pass filters

The properties of dual mode resonance in planar SIW-based rectangular cavities are investigated and discussed. A specific mode combination of dual mode cavity presents a unique frequency response feature. With the aid of an optimization process or software, it is convenient to cascade a number of cavities with coupling apertures to form a filter. A 3-cavity pseudo-elliptic SIW filter based on H203 & H104 hybrid resonance is designed and fabricated on a Rogers TMM3 substrate. Measured results show that the insertion loss at the central frequency around 24 GHz is 4.58 dB and the return loss is better than 20 dB in the whole pass-band of 760 MHz. The design method can widely be used for high-density microwave integrated circuits and the mass-fabrication of such filters is made easy even when keeping development and processing costs very low.