Design of microstrip tri-band bandpass filter using square ring loaded resonator

Abstract

2014)Design of microstrip tri-band bandpass filter using square ring loaded resonator, In this paper, a microstrip tri-band bandpass filter (BPF) utilizing square ring loaded resonator is proposed. A pair of bent perturbation stubs is installed to the ring resonator so as to control resonant modes of the ring. The first three modes are used for tri-band BPF design. In order to control the second and third resonant modes, two pairs of square patches and loaded open stubs are added, and then two asymmetric resonators are cascaded for tri-band operation. Based on the transmission line theory, even-and odd-mode analysis method is used to deduce the resonant frequencies.According to the resonant conditions, a kind of tri-band BPF can be flexibly designed. Finally, two filters are designed as examples in a comprehensive way for demonstration, and one design with passbands located at 2.4, 3.5 and 5.2 GHz is fabricated. Measured results agree well with the simulated ones. IntroductionIn modern wireless communication systems, the tri-band bandpass filters (BPFs) have garnered a lot of attention over the past few years. Many papers show that several approaches have been developed for achieving tri-band operation in BPFs. Stepped impedance resonators (SIRs) are usually used to construct tri-band BPFs due to their controllable multiband behaviours.[1-8] Generally, at least two resonators are utilized to form a tri-band response,[1,2] thus leading to a large circuit size. To reduce the overall size, embedded resonator was explored and developed.[3,4] Short-ended SIR, [5][6][7][8] can also be used to construct tri-band operation and more compact BPFs have been reported. [7,8] Other method, such as nested dual-mode defected ground structure resonators (DDGSRs)[9] and ring resonator,[10] are also developed for tri-band design. Both of them have a very compact size, but the structure in [9] is complex and the three resonant frequencies in [10] are not controllable since the higher resonant modes are the spurious of the fundamental resonance of the ring. Additionally, extra passband can be obtained by adding shunt open stubs to the asymmetric half-wavelength resonators. [11] The idea of using spurious degenerate modes of a ring, [10] and adding open stubs, [11] to form a frequency controllable tri-band BPF is enlightening. Based on this concept, a tri-band BPF utilizing square ring loaded resonator (SRLR) is presented in this

Tri-Band BPF With Six Transmission Zeros Based on Quad-Mode DGS Resonator and Msir

“…In [4][5][6][7], dual-mode, triple-mode, and quad-mode DGSRs were proposed to design BPFs with wide and flexibly controllable bandwidth (BW). On the other hand, the multimode stepped impedance resonator (SIR) has long been utilised to design muliband microwave filters with high performance since it was first systematically investigated in [8]; e.g., in [9][10][11], dual-band, tri-band, and quint-band BPFs were proposed based on a variety of specially designed multimode SIRs. Owing to the potential two layers on both top and bottom of the substrate, DGSRs can be efficiently utilised to design multiband filters.…”