A tunable third‐order bandpass filter based on combining dual‐mode square‐shaped substrate integrated waveguide resonator with triangular‐shaped resonator

Abstract

A frequency reconfigurable third-order bandpass filter based on two substrate integrated waveguide (SIW) cavities is presented in this article. The purposed filter consists of a dual-mode square-shaped resonator and a triangular-shaped resonator. In the square-shaped cavity, four lumped capacitors are loaded as electrical tuning elements in the area where the electric fields of diagonal TE 201 and TE 102 modes are strongest. And an another capacitor is loaded at the suitable region of the triangular-shaped cavity. Square-shaped cavity introduces two transmission zeros and the triangular-shaped cavity can suppress out-of-band spurious modes. The method that combines the resonators with different shapes and multiple modes into an organic whole cannot only achieve synchronous tuning but also have complementary advantages and improve out-of-band rejection. To verify its practicality, a SIW reconfigurable bandpass filter is simulated when the capacitance value varies from 0 to 1.4 pF and measured at 0.7, 0.8, and 0.9 pF, respectively. Measured results show that when the center frequency is tuned from 3.42 to 3.52 GHz, the proposed filter exhibits good tuning performance with insertion loss of less than 2.5 dB and return loss of better than 10 dB, which is suitable for fifth-generation communication system.

Independent Control over Passbands in Highly Selective and Compact Triple-band Bandpass Filter Based on Substrate Integrated Waveguide

“…Electric tuning elements are mostly preferred by researchers, due to their operational ease with controlling voltage used to control the CFs of multiple bandpass filters. Surface mount capacitors, stub capacitors, lumped capacitors, and piezoelectric actuators are some fascinating electric tuning elements used to control the CFs of the passbands [17][18][19][20][21][22][23][24][25][26][27]. The criticality of these tunable bandpass filters lies in the implementation of their electric tuning elements which are sometimes quite complex and hard to operate [17,19,22,23,26,27].…”