A novel wideband bandpass filter based on CSRR‐loaded substrate integrated folded waveguide

Abstract

A novel wideband bandpass filter based on folded substrate integrated waveguide (FSIW) is presented in the article. Five square complementary splitring resonators (CSRRs) are etched in the middle layer of the FSIW. By adjusting the physical size of the CSRR structure, the resonant frequency of the CSRRs can be tuned at the same time and the stopband performance can be changed. As transverse electromagnetic (TEM) mode can be transmitted in the stripline, FSIW excited by stripline shows wider passband than that excited by microstrip line directly. To achieve perfect impedance matching, two microstrip lines to stripline transitions are added in two ports of the filter. The proposed bandpass filter exhibits compact size, high selectivity, good stopband rejection, lower radiation loss, and wideband performances. The measured results show that the fractional bandwidth of the filter is about 35.5%. The measured return loss is better than 15 dB from 4.84 GHz to 6.90 GHz, and the insertion loss is less than 1.2 dB. The comparison between the simulated results and the measured ones validate the possibility of the technology that combines the FSIW and CSRR. K E Y W O R D Sbandpass filter, compact size, complementary split-ring resonators (CSRRs), folded substrate integrated waveguide, radiation loss

High selectivity wideband BPF with very wide stopband characteristic

“…Table 1 compares the performance of the proposed filter with other planar microstrip wideband filters published recently. Compared to the cited References 1‐11 the proposed filter has a significantly sharper selectivity, comparable passband insertion‐loss, and a significantly wider stopband. In particular, the selectivity factor of the proposed filter of 93% is much better than that obtained with the high‐temperature superconductor bandpass filter whose selectivity is 87.9% 11 .…”

“…This filter has a 3‐dB fractional bandwidth of 28.3% and insertion‐loss of 0.91 dB. In Reference 4, a wideband bandpass filter is based on folded substrate integrated waveguide (SIW), where five square complementary split‐ring resonators are etched in the middle layer of the waveguide. The resonant frequency of the resonators and the filter's stopband performance can be changed by adjusting the physical size of the resonators.…”

“…Recently, several wideband filters have been developed 1‐5 . In Reference 1, the wideband filter design uses three‐mode dual‐ring resonator, where the resonator is constructed from two quarter wavelength transmission‐lines and a cascaded half wavelength dual‐ring.…”

A sixth‐order SIW bandpass filter based on combining single‐ and dual‐mode cavities with high selectivity at Ka‐band

“…In comparison with Reference [13], the filter has wider bandwidth and more TZs. Compared with Reference [18], the filter has lower radiation, lower insertion loss and steeper suppression. Compared with Reference [19], the filter has steeper suppression, more TZs and wider bandwidth.…”

A Novel Miniaturized Image Rejection Bandpass Filter Basing on Stepped-impedance Resonators

“…While waveguide filters offer low insertion loss, high selectivity, and excellent stopband rejection, they are not suitable for miniaturized devices due to their large size. In [5], a wideband bandpass filter is established by etching a square Complementary Split Ring Resonator (CSRR) structure in the middle layer of Folded Substrate Integrated Waveguide (FSIW). The innovation of this structure lies in its ability to maintain the integrity of the planar surface, allowing seamless integration with other planar circuits.…”