Compact Dual-Band Bandpass Filter Based on Substrate Integrated Waveguide Cavity With High Selectivity

Abstract

A compact dual-band bandpass filter implemented with an embedded coplanar waveguide (ECPW) resonator and a capacitively loaded resonator (CLR) in substrate integrated waveguide (SIW) cavity is presented and analyzed in this paper. Three transmission zeroes (TZs), of which two are located in the middle of the two passbands and one located in the upper stopband, are obtained to improve the inner-band isolation and the selectivity of the filter. The center frequencies and bandwidths of the two passbands can be easily tuned by changing the geometrical parameters of the two resonators. The proposed dual-band SIW filter is demonstrated with center frequencies located at 8.41/14.29 GHz. The measured insertion loss is −1.28/ − 1.91 dB with the corresponding fractional bandwidth (FBW) of 21.2%/7.3%. The measured results are in good agreement with the simulated ones.

Dual band bandpass filter based on substrate integrated waveguide loaded with mushroom resonators

“…The 3 dB fractional bandwidth of first passband is 12.5% and that of second passband is 10.5% which is quite wide compared to 3 dB FBW of other filters . The proposed dual bandpass filter undergoes a measured insertion loss of 1 and 1.8 dB in first and second passband, respectively, which is relatively less than those filters proposed in References and nearly similar to that of the other filters listed in Table .…”

“…The proposed dual‐band bandpass filter is a second order direct coupled filter with two passbands centered at a close difference of 1.9 GHz compared to other dual passbands having greater difference in center frequencies with orders of 2 and 3 . The comparison table also shows that the proposed filter generates highly selective passband response due to generation of three transmission zeros, compared to the dual passband filters presented in References and maintains the passband selectivity almost similar to the filters proposed in References . The 3 dB fractional bandwidth of first passband is 12.5% and that of second passband is 10.5% which is quite wide compared to 3 dB FBW of other filters .…”

“…A comparison of the proposed work with other types of dual passband filters is listed in Table I which shows the beneficial characteristics of the proposed filter compared to other dual passband filters. The proposed dual‐band bandpass filter is a second order direct coupled filter with two passbands centered at a close difference of 1.9 GHz compared to other dual passbands having greater difference in center frequencies with orders of 2 and 3 . The comparison table also shows that the proposed filter generates highly selective passband response due to generation of three transmission zeros, compared to the dual passband filters presented in References and maintains the passband selectivity almost similar to the filters proposed in References .…”

“…Very recently, direct and cross coupling among multiple SIW cavities are employed to generate dual passband with fixed operating frequency, bandwidth and asymmetric frequency responses . Moreover, highly selective dual passbands are generated by using the excited dual modes of SIW cavity and owning the ability to independently regenerate the resonating modes are proposed in recent times, which conciliate with the asymmetric frequency response . Also there are filter structures based on SIW cavity as well as mushroom resonators that generate triple passband either by perturbing the excited modes of the cavity or by utilizing the electric, magnetic and mixed coupling between adjacent resonators .…”

“…[18][19][20] Moreover, highly selective dual passbands are generated by using the excited dual modes of SIW cavity and owning the ability to independently regenerate the resonating modes are proposed in recent times, which conciliate with the asymmetric frequency response. 21,22 Also there are filter structures based on SIW cavity as well as mushroom resonators that generate triple passband either by perturbing the excited modes of the cavity or by utilizing the electric, magnetic and mixed coupling between adjacent resonators. 23,24 Thus the idea of developing compact bandpass filters using either SRRs or CRLH resonating structures are quite convincing.…”