Design Of Miniaturized Dual-band Bandpass Filters Based On Multi-Mode Resonators

In recent years,with the advent of the intelligent age,wireless communication technology has also undergone rapid iterative updates.At present,the downward compatibility of communication systems with a variety of new and old communication protocols has become the top priority in the history of communication development,and this will inevitably lead to an increasingly tense phenomenon of spectrum resources.Filters are important passive components in microwave integrated circuits and also affect the performance of radio frequency transceivers.Therefore,the realization of miniaturized filters that can work in multiple frequency bands has increasingly become a research hotspot.The coupling of different modes in the multi-mode resonator is a key technology to reduce the number of traditional filter resonators,and it provides an effective design method for realizing the double passband and miniaturization of the filter.The research work of this paper based on the multi-mode resonator to realize the miniaturized dual-band filter is mainly divided into three parts:1.Design of miniaturized dual-band filter based on dual-mode ring and CPW feeding: First,the arrow structure is added to the four inner corners of the traditional dual-mode ring resonator to realize the equivalent capacitance.The equivalent capacitor can adjust the resonance frequency to achieve the miniaturization of the overall structure of filter.The electromagnetic simulation software is used to analyze the physical size parameters and resonance characteristics of the dual-mode ring.Secondly,the coplanar waveguide(CPW)feeding has a wider range of quality factor compared with the parallel coupling feeding,so the coplanar waveguide feeding has better electrical performance.Finally,a dual-band filter is designed based on the coplanar waveguide feed and two dual-mode ring resonators.2.Design of dual-band filter based on Stubs-Loaded quad-mode resonator and halfwavelength resonator: Two theoretical analyses of odd-even modes are carried out on the StubLoaded resonator,and the relationship between the four mode resonance frequencies and the physical size of each stub of the resonator is deduced.The introduction of the half-wavelength uniform impedance resonator and the two open-circuit stubs of the quad-mode resonator are coupled in parallel to form the second bandpass of the filter.The impedance matching of the second passband is realized by loading an open stub in the middle of the half-wavelength resonator,which is beneficial to adjust the return loss of the second bandpass.3.Design of single-and dual-band filters based on the substrate integrated waveguide circular quad-mode resonator:The mode analysis of the circular substrate integrated waveguide quad-mode resonator is carried out firstly,and then the transmission responses of the four modes are obtained under the feed of different symmetrical surfaces.Single-bandpass filter and dual-band filter are designed according to the transmission response characteristics of four modes.Secondly,the X shape slot-line on the resonator can prolong the surface current,which makes the frequency of the filter controllable.