Bandpass filters using multi‐mode square ring resonators

Abstract

A novel scheme of a multi‐mode square ring resonator (MMSRR) is proposed in this study. To analyse the characteristics of the proposed resonator, the odd‐ and even‐mode based method is used, which shows that the basic type of resonator has five resonant modes and three transmission zeros (TZs). The frequencies of the transmission poles and TZs can be changed by varying the sizes of the transmission lines of the resonator flexibly. By varying properly the parameters of the resonator, a dual‐band bandpass filter (BPF) is designed with central frequencies of 1.78 and 3.04 GHz, respectively. To explore further the performance of the proposed MMSRR, two single‐band BPFs with controllable bandwidth are designed. The bandwidth of the filter can be tuned in the range of 138.6 MHz by changing only the characteristic impedance of middle microstrips, which is much higher than previous works. Furthermore, to improve the band‐to‐band isolation of dual‐band filters, a stub is imposed in the middle of the proposed resonator, which can improve significantly the band‐to‐band isolation. Simulation and measurement results show that the isolation is >26.3 dB. The results of the simulation and measurement are in good agreement.

Microstrip quad‐channel diplexer using quad‐mode square ring resonators

“…Once the values of the CFs and FBWs are fixed, the parameters of the BPFs can be determined according to Equations . The corresponding physical dimensions of the BPFs can be calculated accordingly.…”

“…Once the values of the CFs and FBWs are fixed, the parameters of the BPFs can be determined according to Equations 1 and 2. 11 The corresponding physical dimensions of the BPFs can be calculated accordingly. In order to reduce the impact of impedance discontinuities and bends, the physical dimensions should be optimized by changing the lengths and widths of every section in QMSRR.…”

“…In microstrip based multiplexers, a popular way to reduce the overall size is to use multi‐mode stub loaded resonators . Another one is to adopt square ring resonators, which have higher design freedom than the stub loaded resonator . However, an input matching network is still used in the square ring resonator based multiplexers, which consist of several bandpass filters in usual.…”

“…4,[7][8][9] Another one is to adopt square ring resonators, which have higher design freedom than the stub loaded resonator. 10,11 However, an input matching network is still used in the square ring resonator based multiplexers, 10,11 which consist of several bandpass filters in usual. The matching network serves as a through pass at the center frequency (CF) of a bandpass filter and provides a short circuit at the CF of another bandpass filter.…”

Individually controllable dual-band bandpass filter with multiple transmission zeros and wide stopband

“…Dual-band bandpass filters (DB-BPFs) with controllable dual-passbands and wide stopband play an important role in low interference and multiservice wireless communication systems, and up to now, many design methods have been proposed with insert a bandstop performance resonators [1,2], consist of two different size or type resonators with common feed structure [3,4,5,6,7], stepped-impedance resonators (SIRs) [8,9,10,11], stub-loaded resonators (SLRs) [12,13,14,15,16,17,18,19,20,21], other types multi-mode resonators (MMRs) [22,23,24,25], and substrate integrated waveguide (SIW) structures [26,27]. In [1], a synthesizing method is presented to design dualband by consist of a wideband bandpass filter and a stopband filter.…”