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     

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.     

Dual-mode microstrip bandpass filter using ring of arrows resonator

A dual-mode microstrip bandpass filter using the degenerate modes of a modified square ring structure is proposed. The size of the new structure is 50% less than conventional dual-mode bandpass microstrip square resonator filters at the same centre frequency. Measurements are in good agreement with designed values.     

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     

A reduced-size dual-mode bandpass filter with capacitively loaded open-loop arms

A novel type of dual-mode microstrip bandpass filter using degenerate modes of a dual-mode microstrip square loop resonator with capacitively loaded open-loop arms is proposed. Such a dual-mode bandpass filter with a 0.75% bandwidth at the center frequency of 1.603 GHz is designed and fabricated to demonstrate the design of reduced-size microstrip filters. It is shown that the proposed filter has a size reduction of about 59% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop and ring resonator filter.     

A novel dual-mode bandpass filter with wide stopband using the properties of microstrip open-loop resonator

A novel dual-mode microstrip square loop resonator is proposed using the slow-wave and dispersion features of the microstrip slow-wave open-loop resonator. It is shown that the designed and fabricated dual-mode microstrip filter has a wide stopband including the first spurious resonance frequency. Also, it has a size reduction of about 50% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop, and ring resonator filter.     

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     

A Balun-BPF Using a Dual Mode Ring Resonator

In this letter, a Balun-bandpass filter (BPF) is proposed by using a dual-mode ring resonator. The Balun-BPF is not a simply combined or integrated component of a BPF and a Balun but a single BPF with the balun function. We obtained the proper balanced outputs and two-pole BPF characteristic by symmetrically placing the output ports at lambda/2 distance from each other on the dual-mode ring resonator. The fabricated Balun-BPF has a bandwidth of 40 MHz and an insertion loss of 2.4 dB at a center frequency of 2.45 GHz. The differences between the two outputs are 180-184deg in phase and within 1dB in magnitude. The measured frequency responses agree well with simulated ones.     

Dielectric-ring-loaded waveguide feed

A dual-mode waveguide loaded with a dielectric ring has been optimised to give symmetrical field patterns in the E- and H-planes and very low crosspolarisation. The v.s.w.r. and phase patterns are also described. The device satisfies the requirements of a feed for deep reflectors.     

In-Line Waveguide Selective Linear Phase Filters

A procedure is described whereby narrow-band waveguide selective linear phase filters may be designed from a low-pass prototype linear phase network. The structure is comprised of a cascade connection of basic sections, each containing a direct-coupled cavity together with a dual-mode resonator. Each dual-mode resonator takes the form of a square guide mounted on the broad wall of the main rectangular guide and coupled to this guide by a small aperture. Explicit formulas for the susceptance of the coupling apertures and electrical lengths of the cavities are given in terms of the low-pass prototype.     

A dual-mode bandpass filter with enhanced capacitive perturbation

A dual-mode ring bandpass filter with two pairs of capacitors has been designed. The capacitors are used to control the location of the even- and odd-mode frequencies independently, allowing weak coupling for narrow-band filter design with realizable capacitance values. Theoretical expressions have been derived for these frequencies. A 4% bandwidth bandpass filter centered at 1.9 GHz was designed and tested with good agreement between theoretical and measured results.     

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     

A novel compact ring dual-mode filter with adjustable second-passband for dual-band applications

In this letter, a novel compact ring dual-mode with adjustable second-passband for dual-band applications are presented. A ring resonator with two different geometric dimensions are derived and designed to have identical fundamental and the first higher-order resonant frequencies, and to establish appropriate couplings in the structure. Moreover, the proposed filter has smaller size as compared with the basic topology of stopband filters and stepped-impedance-resonator (SIR) filters. The measured filter performance is in good agreement with the simulated response.     

新型微扰结构双模贴片带通滤波器设计

针对微带滤波器高性能小型化的需求,提出了一种方环形微扰单元的双模贴片带通滤波器的设计.该滤波器由方形贴片作为谐振器,输入、输出端口采用直接馈电,具有对称结构.利用在方形贴片上蚀刻出方环形缺口的方式,对方形贴片谐振器进行微扰,实现双模滤波器.通过电磁仿真软件Ansoft HFSS分析了微扰单元的特性,对双模滤波器的性能进...     

Quarter-Wavelength Side-Coupled Ring Resonator for Bandpass Filters

This paper deals with a dual-mode ring resonator fed by quarter-wavelength side-coupled lines. The resonator synthesis was developed so as to fix the central frequency, bandwidth, and transmission zeros frequencies, as well as the insertion loss in the passband. Based on this resonator, several bandpass filters were designed, which include the cascaded rings and the combination of such ring resonator with coupled line sections. Simulations are proposed throughout the paper to illustrate the various possibilities offered by the concept. The filters' experimental results in microstrip technology are also presented to validate the idea.     

A Novel Dual-Mode Dual-Band Bandpass Filter Based on a Single Ring Resonator

A dual-mode dual-band bandpass filter with two transmission poles in both passbands using a single ring resonator is proposed. Two excited ports are placed at the 135$^{circ}$ -separated positions along the ring resonator and coupled with the ring via parallel-coupled lines, leading to synchronous excitation of two transmission poles in dual passbands. After the principle of this initial filter is described, an improved ring resonator with periodic loading of open-circuited stubs is constructed and studied to achieve compact size and adjustable spacing between the two passbands. Finally, a dual-band ring resonator filter with center frequencies at 2.4 and 5.8 GHz is designed and fabricated. Measured results verify the design principle.      

A novel self-coupled dual-mode ring resonator and its applications to bandpass filters

A novel dual-mode ring resonator with self-coupled segments, called a self-coupled ring resonator, is proposed. The self-coupling between ring segments provides the same mode perturbation effect as the conventional methods of adding stub, cutting notch, or varying line impedance on the ring resonator. The mode perturbation and transmission-zero generation due to the self-coupling effect are analyzed with the even-odd mode theory. The self-coupled ring resonator can have the capacitive or inductive perturbation simply by controlling the impedance ratio and coupling coefficients of self-coupled sections. For both perturbation cases, the transmission zeros exist at even multiples of the passband center frequency, resulting in wide stopband range. Also, only for the capacitive perturbation case, two transmission zeros are found on both sides of the passband, which brings a pseudo-elliptic bandpass response. In comparison with the regular uniform ring resonator, the self-coupled ring resonator takes shorter ring length, giving the compact size feature when applied to a bandpass filter design. A 2.45-GHz low-temperature co-fired ceramic bandpass filter based on the self-coupled ring resonator was designed to verify the proposed theory.     

60-GHz Band Dual-Mode Microstrip Ring Resonator Bandpass Filter Using Micromachining Technology

A new compact millimeter-wave dual-mode ring resonator bandpass filter is proposed. This filter has a 15% bandwidth at 58 GHz with 3.4 dB insertion loss. Input/output lines and ring resonator are directly connected to obtain tight coupling, and an open-end stub is inserted for dual-mode operation. This filter is fabricated on a GaAs wafer by using MEMS technology and can be applied for the millimeter- wave SoC.     

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.