Dual-Band Substrate Integrated Waveguide Filters with Independently Controllable Passband Based on Cambered Cavity and Circular Cavity

In this brief, a new type of dual-band substrate integrated waveguide (SIW) filter based on cambered cavity and circular cavity are proposed. An additional transmission path is obtained through the combination of the circular cavity and cambered cavity, thus the second passband can be produced and the independent tunability can be achieved. The quasi TE
102
mode or quasi TE
103
mode can be selected as the second passband to achieve different frequency ratios by changing different feeding lines positions. Meanwhile, the unwanted frequency is suppressed. The dual-band filter I based on quasi $\mathrm{TE}_{\mathrm{101}}$ mode and quasi TE
102
mode and the dual-band filter II based on quasi $\mathrm{TE}_{\mathrm{101}}$ mode and quasi TE
103
mode are synthesized, fabricated, and measured. According to the measurements, the 3-dB fractional bandwidth (FBW) are 5%/4.1% of dual-band filter I and 5%/2.8% of dual-band filter II. The frequency ratio is 1.11 and 1.24 respectively.