Dual- and Triple-Mode Branch-Line Ring Resonators and Harmonic Suppressed Half-Ring Resonators

Ring resonators have been widely used for various applications. Dual-mode ring resonators have also been investigated due to their applicability to multifrequency mode requirement. In this paper, dual-mode ring resonators using a branch line are designed along with a systematic approach. Triple-mode branch-line ring resonators are also designed adding two branch lines to the ring resonator. Adding more branch lines, multimode resonators can be realized based on the design procedure developed here. The location of the branch lines determines the additional resonant frequencies other than the fundamental resonant frequency generated by the enclosing ring. Furthermore, half-ring resonators working at 2.5 GHz are proposed for suppressing multiple harmonics (second and third harmonics) and providing size reduction with employment of various physical configurations. Equalizing the even- and odd-mode phase delays, harmonics are suppressed effectively in the design of half-ring resonators. Double half-ring resonators with a long opening gap are investigated to continuously decrease the resonant frequency. An open-loop structure provides flexible design and lowers the resonant frequency. Two dual-mode ring resonators and one triple-mode ring resonator are simulated and fabricated along with three different half-ring resonators     

A new type of waveguide ring cavity for resonator and filterapplications

A new type of rectangular waveguide ring cavity has been developed for applications to resonators, filters, and multiplexers. The circuits have advantages of high Q and high power handling capability. H-plane and E-plane waveguide ring cavities have been investigated thoroughly in single-mode and dual-mode operations. For single-mode operation, regular resonant modes, split resonant modes, and forced resonant modes were explained by resonant mode charts of E-field points. Mechanically tuned and electronically tuned resonators built by adjusting the resonant modes between regular resonant modes and forced resonant modes have been demonstrated. For dual-mode operation, a dual-mode filter using a single H-plane ring cavity has been built with a bandwidth of 0.77%, a stopband attenuation of more than 40 dB, and a sharp gain slope transition. Another dual-mode filter which was formed by cascading two E-plane ring cavities has also been fabricated with a bandwidth of 1.12%, a stopband attenuation of 70 dB, a mode purity of 2 GHz at the center frequency of 26.82 GHz, and a sharp gain slope transition     

双模方形谐振腔增益均衡器的设计与实现

针对均衡器小型化、高Q值的应用需求,提出并设计了一个工作在Ku波段的双模方形基片集成波导谐振腔均衡器.设计了两个正交的耦合缝隙,在谐振腔中激励起简并模TE₂₀₁和TE₁₀₂;使用金属柱微扰其中一个模式,实现独立调节该模式的谐振频率,并且频率调节自由度高;研究了薄膜电阻的加载位置,实现独立调节两个模式的衰减量和Q值;分析了双模谐振腔级联后谐振频率偏移量及可调性,给出了双模谐振腔均衡器的分析和设计方法.相比于传统单模谐振腔均衡器,该结构均衡器保持了原有的工作性能,并减少了一半数量的谐振腔,使得结构更加紧凑.测试结果与仿真结果吻合,最大误差0.4dB.     

Reducing electrical size of metamaterial elements: simulations and experiments

A simple realisation of split ring resonators with small ring diameter/ wavelength ratio (~ 1/300) is investigated. Theoretical, numerical and experimental analysis have been used and the results from all studies exhibit good agreement. Initial fabrication techniques are developed; however, further high resolution techniques can enhance the performance of the resonators. This class of small resonators with low resonant frequencies shows broad application promises in the design of microwave devices, e.g. filters and antennas in mobile phones, MRI sensors and metamaterial structures.     

A joint field/circuit model of line-to-ring coupling structures andits application to the design of microstrip dual-mode filters and ringresonator circuits

A joint field/circuit model is proposed in this paper to characterize a class of line-to-ring coupling structures for design and optimization of microstrip dual-mode filters and ring resonator circuits. The generic model is derived from field theory and presented in terms of circuit elements by applying a newly developed numerical deembedding technique called “short-open calibration” in a deterministic method-of-moments scheme. It provides a new design strategy for characterizing and optimizing electrical performance of the line-to-ring coupling structures. Such three-port topologies are explicitly formulated by using an equivalent network having circuit elements calculated by the proposed joint field/circuit model. Three microstrip tightly coupling geometries and their related ring resonators are studied with the extracted J-inverter susceptance parameters. Experiments are performed to validate the joint model and also show coupling characteristics of the three types of line-to-ring circuit for the design of ring resonators and dual-mode filters. With this new technique, an optimized microstrip dual-mode filter is successfully designed and the prediction agrees well with our measurements     

Microwave circuit theory-based models to predict the resonant frequencies of a wide range of ring resonators

The concept of the ring resonance of a symmetric two-port network is used to determine the resonant frequencies of a variety of ring resonators, on the basis of simple transmission-line or coupled-transmission-line equivalent circuits. Several illustrative structures, from the closed ring microstrip to the Pendry-type split-ring slotline resonators, have been analysed and measured. Full-wave simulations and measurements are in excellent agreement with the proposed models, and even with its short-line approximations, when suitable.     

Dual-mode quasi-elliptic-function bandpass filters using ringresonators with enhanced-coupling tuning stubs

A novel microwave dual-mode quasi-elliptic-function bandpass filter structure has been designed and fabricated. The filter uses L-shaped coupling arms for enhanced coupling and dual-mode excitation. The effects of varying the length of tuning stubs and gap size between tuning stubs and ring resonator have been studied. Filters using multiple cascaded ring resonators with high rejection band are presented. The new filters have been verified by simulation and measurement with good agreement     

微波线性相位双模介质滤波器

本文讨论了用双模介质加载谐振腔实现的微波线性相位滤波器结构，在非级联耦合的诸振腔之间引入一个交叉耦合，以改善通带内的时延平坦特性，给出了用模匹配法计算介质加载谐振腔的谐振频率和谐振腔之间耦合系数的方法。介绍了采用这种方法构成的滤波器的实际设计方法。最后制作了用这种方法设计出的滤波器，给出的实测结果表明它不仅可满足幅频特性的滤波要求，而且具有良好的通带时延特性。     

Novel Dual-Mode Dual-Band Filters Using Coplanar-Waveguide-Fed Ring Resonators

This paper presents a novel approach for designing dual-mode dual-band bandpass filters with independently controlled center frequencies and bandwidths. Two microstrip perturbed ring resonators are employed to obtain dual-mode dual-band responses. Novel feeding structures are introduced to simultaneously feed the ring resonators and conveniently control the coupling strength between resonators and feeding lines, resulting in a wide tunable range of external quality factors. Two kinds of filter configurations with compact size are proposed. Both of them provide sufficient degrees of freedom to satisfy various requirements of external qualify factors and coupling coefficients at both passbands. Therefore, the center frequencies and fractional bandwidths of both passbands can be independently tuned to desired specifications within a wide range. To verify the proposed method, four filters are implemented. The measured results exhibit dual-mode dual-band bandpass responses with high selectivity.     

Theory and experiment of dual-mode microstrip triangular patch resonators and filters

In this paper, we report on the results of an investigation into dual-mode operation of microstrip triangular patch resonators and their applications for designing dual-mode bandpass filters. It has been found theoretically that the dual modes can result from the rotation and superposition of a fundamental mode. The characteristics of the dual modes and their mode splitting are described. The applications of this new type of dual-mode microstrip patch resonator in the design of microwave planar filter are presented. A circuit model for operation of this type of filter is proposed. Two- and four-pole filters of this type are demonstrated for the first time. Both theoretical and experimental results are presented.     

Novel Dual-Mode Bandpass Filters Using Hexagonal Loop Resonators

Novel dual-mode hexagonal loop resonators with the patch and notch perturbation are proposed in this paper. The field patterns of the degenerate modes and their mode splitting characteristics are investigated. The applications of the dual-mode hexagonal loop resonator as bandpass filters are presented. It is shown that different responses can be realized using only a single dual-mode resonator by changing the position of the perturbation. A coupling and routing scheme is presented to model the operations of these filters. Two- and four-pole filters of this type are demonstrated for the first time. All the theoretical analysis and design procedures have been verified by experimental results.     

Microwave resonators with dual-mode oscillations

Analysis of microwave resonators with dual-mode oscillations is conducted. A new type of resonators is discovered in which dual-node oscillations are observed. It represents a half-wave resonator with a short-circuit in the middle part. The length of such a resonator is twice less than the length of a widely used ring resonator. It is shown that in resonators of the loop type combined frequency tuning of dual-mode oscillations is accomplished using capacity and inductance. In the loop-type resonators with a stub frequency tuning of dual-mode oscillations is accomplishing with two capacities synchronously changing their values according to a specific law. Resonance equations are obtained.     

Loop-Gap Resonator: A Lumped Mode Microwave Resonant Structure

Loop-gap resonators are newly developed microwave resonant structures with a field configuration that is intermediate between lumped and distributed. Typical characteristic dimensions are of the order of 1/10 of the resonant wavelength, and typical Q's are of the order of 1600-2000 in the frequency range of 1-4 GHz. Data are presented for Q's and frequencies for a series of resonators of various dimensions and compared with theory. Various coupling and frequency tuning techniques are discussed, and results of experiments are reported. Results of preliminary application of the stictire in microwave filters and oscillators are presented. Loop-gap resonators provide a useful design alternative, it is concluded, to dielectric and surface acoustic-wave resonators at low microwave frequencies.     

Millimeter-Wave Ultra-Wideband Bandpass Filter Employing Dual-Mode Ring Resonators Fed by Step-Impedance Coupled Lines

This paper presents a novel millimeter-wave ultra-wideband (UWB) bandpass filter (BPF) based on microstrip dual-mode rectangular ring resonators. In order to get strong coupling between the input/output line and the dual-mode ring resonators, a step-impedance parallel-coupled structure is adopted for the design of the filter. On the other hand, transmission zeros are produced by the dual-mode resonator. As a consequence, the filter has low insertion-loss in its passband, sharp attenuation in its lower and upper stopbands and very wide stopbands. As an example, a filter with two dual-mode ring resonators is designed and fabricated. The measured frequency property of the fabricated filter shows good agreement with the simulated response.     

Realization of a dual-mode bandpass filter exhibiting either a Chebyshev or an elliptic characteristic by changing perturbation's size

A dual-mode resonator with square patches attached to inner corners of a conventional microstrip loop resonator is proposed. The two types of coupling between the degenerate modes are described by changing the perturbation's size for realization of either a Chebyshev or an elliptic function filter. A novel type of dual-mode microstrip bandpass filter using degenerate modes of this type of dual-mode resonators is developed. It is shown that the perturbation's size determines the filter characteristic, whether it is Chebyshev characteristic or elliptic characteristic.     

Intelligence method for optimizing a microstrip filter based on folded dual-mode resonators

An efficient method for optimizing microwave filters based on dual-mode resonators has been developed. In this method, a prior knowledge of how the passband parameters depend on the resonators’ resonant frequencies and couplings is used. It is shown that the rules for the intelligence optimization of filters, previously formulated for single-mode resonators, can also be applied to dual-mode resonators. To this end, each dual-mode resonator of the filter should be put into correspondence with its proper pair of imaginary single-mode resonators whose coupled-oscillation frequencies coincide with the frequencies of the dual-mode resonator.     

Left handed coplanar waveguide band pass filters based on bi-layer split ring resonators

A new type of compact band pass filters based on planar structures with three metal levels is proposed. The central layer consists on a coplanar waveguide (CPW) with periodic wire connections between the central strip and ground planes. In the upper and lower metal levels, split ring resonators (SRRs) are etched and aligned with the slots. The wires make the structure to behave as a microwave plasma, with a negative effective permittivity covering a wide frequency range. SRRs, which are magnetically coupled to the CPW, provide a negative magnetic permeability in a narrow frequency range above their resonant frequency. The result is a band pass structure which supports wave propagation in a frequency interval where negative permittivity and permeability coexist. The bandwidth of the structure can be controlled by tuning the resonant frequency of the upper and lower SRRs and the distance between SRRs. Fabricated prototype devices exhibit very low insertion losses in the pass band (<1.5 dB) and high frequency selectivity.     

太赫兹多波段的电磁诱导透明设计与分析

设计了一种超材料三维模型,由闭合方环和4个开口谐振方环通过正、反向双开口方环与闭合方环相互耦合来组成,在太赫兹范围内具有多波段电磁诱导透明(EIT)效应。该结构分别实现了在1.21、1.46、1.61、1.98 THz这四波段的电磁诱导透明现象,并且谐振强度均达到0.9左右。通过将结构单元进行拆分并相互对比分析,研究了该超材料结构产生多波段EIT效应的物理机理,并重点分析了开口大小、闭合方环尺寸对EIT强度与带宽的影响。通过对三维立体结构仿真分析可知,所设计的超材料不仅在多个波段获得了较高的折射率灵敏度,还具有高强度、多频点的慢光效应。因此,其在折射率传感与光缓存器件等领域,具有良好的应用前景。     

Permeability Measurement of Metamaterials with Split-Ring-Resonators Using Free-Space Calibration-Independent Methods

A calibration-independent microwave method is proposed for complex permeability extraction of metamaterial structures composed of periodic split-ring resonators. For the retrieval process, uncalibrated (raw) complex scattering parameter measurements of three measurement configurations in free-space are utilized. Two metric functions are derived for retrieval of complex permeability of homogeneous metamaterial slabs even when their lengths are unknown. The method is validated by retrieving the magnetic properties of some homogeneous SRR metamaterial slabs with a pre-assigned magnetic resonant frequency.     

谐振器加载石墨烯的双通带可调滤波衰减器设计

石墨烯材料在微波段的阻抗可控特性是其最有价值的应用特性之一。文中首次分析了石墨烯对微带 多模谐振的影响机理,提出了一种集成滤波衰减功能为一体的灵活可控器件。首先,对不同位置加载石墨烯的微带双 模谐振器进行了严格的等效电路建模,通过奇偶模分析法及输入导纳参数计算,探究了双模谐振受石墨烯阻抗及其加 载位置的影响,明晰了石墨烯材料对微波谐振器的影响。随后设计了动态可调的滤波衰减器并阐述了石墨烯材料在谐 波控制上的潜在应用点。最后,采用不同尺寸的双模谐振器进行石墨烯加载并完成双通带幅度独立可控的滤波衰减器 的设计,仿真与实测结果吻合良好,验证了阻抗可控石墨烯材料在可调微波衰减类器件上的应用前景。