Dual-Band Half Mode Substrate Integrated Waveguide Filter With Independently Tunable Bands

In this brief, a dual-mode dual-band filter based on half-mode substrate integrated waveguide (HMSIW) is presented. The proposed filter has the capability to tune the two pass-bands independently. The proposed filter consists of two HMSIW resonators coupled through a pair of E-shaped coupling slots. Two resonating modes (TE
₁₀₁
and TE
₁₀₂
) are excited in each resonator. A varactor diode is used in the proposed filter for tuning purpose. The varactor diode is placed in the structure in such a way that both bands can be tuned independently. The lower passband can be tuned from 3.26 to 3.47 GHz with insertion loss of 0.2-2.9 dB. The higher passband can be tuned from 5.47 to 6.13 GHz with low insertion loss of 0.1-2.1 dB. The presented results show the flexibility of the filter to achieve desired responses and its suitability for integration with any tunable planar structure. A good agreement between the simulated and measured results is observed.