Design of a miniaturized multi resonance resonator based highly selective dual wideband bandpass filter

Abstract

This paper presents the design of a highly selective dual-wideband bandpass filter. The filter is designed by using multi-resonance resonator consisting of two stub-loaded step impedance resonators separated by an inter-digital capacitor. The inter-digital capacitor generates capacitive coupling, resulting in multiple resonating modes. The proposed filter generates two passband frequencies centered at 5.75 GHz and 11.5 GHz. Experimental measurements show that the maximum insertion loss in the passbands is 0.83 dB and 0.87 dB, while the reflection losses are better than 10.8 dB and 12.6 dB, respectively. The resonant frequencies can be adjusted by changing the length of the loaded stubs. The proposed dual-wideband bandpass filter offers improved out-of-band rejection and selectivity by generating seven transmission poles and seven transmission zeros around both passbands. The experimental results confirm the effectiveness of the proposed filter. Furthermore, the filter has a compact size of $(0.61\times 0.66){\lambda }_g$, making it suitable for integration into microwave sensing devices.