A novel coupling structure suitable for cross-coupled filters with folded quarter-wave resonators

A new class of coupling structure for cross-coupled filters with folded quarter-wave resonators is presented. The cross coupling mechanism is realized by magnetic coupling from the short ends of the resonator. The proposed magnetic coupling solves the problem of response limitation of folded quarter-wave resonator cross-coupled filters that were introduced previously using electrical cross coupling. Several quadruplet and trisection filters are proposed and fabricated. The measured results matched well with the theoretical prediction.     

Novel Multifold Finite-Ground-Width CPW Quarter-Wavelength Filters With Attenuation Poles

This paper proposes a novel multifold finite-ground-width coplanar waveguide (CPW) lambda/4 resonator filter that has the capability of realizing attenuation poles by cross coupling of nonadjacent resonators. The newly proposed multifold structures not only greatly shrink the length of a resonator, but also provide a convenient way to implement cross coupling in a filter. The proposed multifold finite-ground-width CPW resonators can have much stronger coupling than that of spiraling and meandering layouts, and any number of folds is possible. Two combline filters are designed and measured with twofold and threefold lambda/4 finite-ground-width CPW resonators. A trisection and a quadruplet generalized Chebyshev filter formed by cross couplings between nonadjacent resonators have been implemented by modifying the layout of the resonator. These filters are smaller in size and have the capability of controlling attenuation poles     

Microstrip Parallel-Coupled Filters With Cascade Trisection and Quadruplet Responses

Microstrip parallel-coupled filters with generalized Chebyshev responses are presented. The basic structure of the proposed filter is a conventional parallel-coupled filter of which the physical dimensions can be easily obtained by the well-known analytical method. With the aid of the equivalent circuit corresponding to a conventional parallel-coupled filter, the relative insertion phase from source or load to each open end of resonators can be easily obtained by observing the two-port admittance matrix. Applying the cross coupling from source or load to a proper nonadjacent resonator, a trisection or a quadruplet coupling scheme can be realized with prescribed transmission zeros. More importantly, the proposed trisection can be designed to have a transmission zero on the lower or upper stopband by just adjusting the length of the cross-coupling strip. Using the proposed structure, the conventional time-consuming adjusting procedure to obtain initial physical dimensions of filters is no longer required. In this paper, a fourth-order parallel-coupled filter is used as the basic structure to demonstrate various combinations of transmission zeros. Simulated and measured results are well matched.      

Synthesis of filters with transmission zeros at real frequencies bymeans of trisections including source/load to resonator coupling

Filter synthesis based on trisections is extended to the case where coupling is between the source/load (input/output ports) and the resonators. Using this coupling, two transmission zeros can be placed at different real frequencies (jw axis of the complex plane) and independently controlled. For odd order filters: a new network transformation between the ladder network and the equivalent trisection is proposed. To validate the above transformation, a fifth degree two-trisection filter has been synthesised     

Design of quasi-elliptic function filters with a dual-passband response

Compact miniaturized hairpin resonators are used to design cross-coupled filters with a dual-passband response of elliptic function type. The hairpin resonators are treated as a stepped impedance resonator (SIR) in analysis. In a filter, two different hairpin resonators are used to establish proper couplings required for the two design frequencies. Two filters are fabricated and measured. The results show a good agreement with the simulation.     

Thin stripline bandpass filters for the centimeter band

This article considers the design of thin stripline (1 mm) bandpass filters in the centimeter band, which contain dielectrics with different relative permittivity ε _r . This includes the choice of the resonators, the dielectric material, the preliminary assessment of resonators’ unloaded quality factors and taking into account the features of the frequency response curve of the filter. It was found, that the passband width of the thin comb filters with λ/4 resonators and array-type filters with λ/2 resonators cannot exceed 6% for any values of ε _r and the length of resonators of at least 2 mm. The array-type filters with resonators of half-wave type and with alternating signs of the coupling factors between resonators were proposed. Under certain additional conditions, the attenuation poles appear in such filters, resulting in improved selectivity. The results of computer modelling of the frequency response curve of thin filters of cm band are presented. They are compared to the frequency response of other filters. The data obtained from computer modelling showed good correspondence with the experimental data.     

Compact Bandpass Filters Based on Dual-Plane Microstrip/Coplanar-Waveguide Structure With Quarter-Wavelength Resonators

Compact wideband bandpass filters are proposed based on the dual-metal-plane structure consisting of both microstrip and coplanar-waveguide (CPW) quarter-wavelength resonators. By combining the advantages of dual-plane microstrip/CPW structure and stepped-impedance resonators, strong couplings between resonators may be accomplished so that the fourth-order cross-coupled filter with compact size and wide bandwidth may be realized. To further improve the selectivity, the sixth-order cross-coupled filter composed of four microstrip and two CPW resonators is implemented. Specifically, the implemented filters have the merits of compact size, good insertion/return losses, wide fractional bandwidth, and better selectivity. Good agreement between simulated and measured responses of these filters is demonstrated     

Compact dual-band bandpass filter using trisection hairpin resonator for GPS and WLAN applications

A compact dual-band bandpass filter using trisection hairpin-shape resonators has been designed and fabricated. Measured results are in good agreement with electromagnetic simulation results and verify that two central frequencies of the fabricated filter are located at about 1.57 GHz (GPS application) and 2.40 GHz (WLAN application). The measured return losses in both 1.57 and 2.40 GHz bands are higher than 16 dB while the measured insertion losses are about 1 dB in the two passbands. The circuit size of the proposed filter occupies only 26 times 26 mm (sime0.22lambda_g times 0.22lambda_g).     

小型化多层带线谐振腔缺陷地结构LTCC宽带带通滤波器

利用多层宽边耦合带状线谐振结构实现小型化LTCC(LowTemperature Co-fired Ceramic)宽带滤波器。采用了两层、三层耦合带线谐振结构,利用这两种谐振结构可以有效减小滤波器的尺寸。利用四个谐振腔结构,实现较宽的频带和较强的选择特性;输出、输入引入电感反馈产生两个传输零点,利用DGS(Defected Ground Struc-ture)可使滤波器在阻带和镜像频率处产生较大的衰减。设计出侧面印刷互连和侧面通孔互连两种工艺结构的滤波器,利用LTCC工艺加工出侧面印刷互连的滤波器性能良好,测试性能和仿真结果基本吻合。     

脊双模波导滤波器的研究

介绍了一种利用脊谐振器产生的正交准TEM简并模实现脊双模波导滤波器的新方法。通过分析脊谐振器放置在主模传输波导中不同位置的特性,建立了耦合拓扑结构图,实现了三种不同类型的频率响应。利用全波仿真软件AnsoftHFSS,分别以方形和十字交叉这两种脊谐振器作为基本单元,设计出了两腔四阶的脊双模波导滤波器,两个滤波器的插损均小于0.2 dB,回波损耗小于–23 dB,仿真结果与预期吻合。     

Modified method for the analysis and design of microwave bandpass filters containing dielectric resonators

High-Q dielectric resonators having remarkable advantages such as compactness, light weight, temperature stability, and low cost have become very valuable elements for various microwave circuits. A modified Itoh and Rudokas model is proposed to analyse the field distribution and the coupling relations between dielectric resonators and microstrip lines based on the analysis results, a convenient procedure for designing microwave filters containing parallel coupled dielectric resonators is presented. Two experimental dielectric resonator filters are also fabricated to verify the calculation and the design procedure. The outcome demonstrates that the procedure provides good accuracy and saves design time.     

RF-MEMS谐振器和滤波器研究进展

介绍了基于梳状、梁式、圆盘三种结构的射频微机电系统( RF-MEMS)谐振器及滤波器,并对RF-MEMS谐振器及滤波器的结构与性能参数进行讨论;分析RF-MEMS谐振器及滤波器设计和制造中的有关问题及其处理方法;RF-MEMS谐振器及滤波器性能优异,能与其他器件实现片上集成,且与集成电路工艺兼容,在射频无线通信系统中的...     

Design of Band-Stop Filters in the Presence of Dissipation

The insertion loss vs. frequency characteristic of equal-element band-stop filters is derived for large as well as small degrees of dissipation, and for any number of resonators. These results are presented as curves for one through eight resonator filters. The equal-element band-stop filter, for small dissipation, is shown to have the lowest pass-band loss for a specified stop-band characteristic of all possible filters that can be represented by a low-pass prototype. Design procedures and examples are explained for waveguide and TEM band-stop filters. This includes selecting the optimum number of resonators, the resonator lengths, and the coupling reactance. Experimental results on C-band waveguide and UHF coaxial filters are presented; the results are in good agreement with the theory. This approach makes possible complete prediction of the filter response and results in lower pass-band loss than could be obtained with previously used approaches.     

Miniaturized hairpin resonator filters and their application toreceiver front-end MICs

The authors describe the fundamental characteristics of miniaturized hairpin resonators having parallel coupled lines and show their applications to bandpass filters and receiver front-end microwave integrated circuits (MICs). A method for calculating filter coupling parameters using a general-purpose microwave circuit simulator is presented. The bandpass filters have a suitable structure for MICs, and their size is one-half that of conventional hairpin resonators without increasing insertion losses. Trial receiver front-end MICs using these filters have been developed and have shown good characteristics such as low noise and a high image suppression ratio. They are applicable to a frequency range above the L-band     

源与负载感性交叉耦合的小型介质滤波器

为了提高滤波器的阻带衰减,研究了源与负载感性交叉耦合的小型介质滤波器。首次提出一种新概念：将源和负载看作准谐振器。以贴片电感作为源与负载之间、源与第二个谐振器之间的交叉耦合元件,两个准谐振器和两个介质谐振器可构成级联四节(CQ),一个准谐振器和两个介质谐振器可构成级联三节(CT)。分析了传输零点的位置,详细讨论了这种滤波器结构的设计方法。采用介电常数为80的介质陶瓷组装了3个两级介质滤波器,并进行测试,结果表明传输零点的个数和位置与仿真设计相符合。滤波器的体积小,均为14 mm×6.5 mm×10 mm。     

基于DSPSL 的电可重构平面带通滤波器

提出基于新型平衡传输线——双面平行带线(DSPSL)结构的电容加载电可重构平面带通滤波器,并以梳状线 和磁耦合谐振环带通滤波器为例验证该方案的可行性。相对于常见的微带线结构,双面平行带线具有对称性以及较高 的功率使用容量。这些特性使得滤波器在没有无限大金属地板的情况下,仍然获得了良好的性能。采用DSPSL 结构 进行微波电路设计不但可以减小电路的尺寸,同时还增加了电路设计的灵活性。     

A class of novel uniplanar series resonators and theirimplementation in original applications

A class of novel millimetric uniplanar series resonators are presented, which can be used in monolithic and hybrid uniplanar microwave integrated circuits (MIC's). The proposed structures are able to demonstrate low radiation and compactness characteristics, which are attractive for passive and active monolithic and hybrid integrated circuits. A principle of achieving these high-quality circuits is described and also confirmed by experimental and theoretical results, which are in good agreement up to 50 GHz. To illustrate the features of the proposed series resonators and demonstrate their effectiveness, two classes of miniature coplanar waveguide (CPW) filters (namely, low-pass and bandpass) are designed using these resonators. The developed low-pass filter has some important advantages such as low insertion loss in passband, very wide stopband, high cutoff rates, small size, low number of elements, and an effective control of spurious signals. On the other hand, the newly developed bandpass filter provides an alternative, yet compact, structure to classical filters. Obviously, many other classes of filters or passive components can also be designed     

Balanced Coupled-Resonator Bandpass Filters Using Multisection Resonators for Common-Mode Suppression and Stopband Extension

Novel fourth-order balanced coupled-resonator bandpass filters are proposed using suitably designed half-wavelength (lambda/2) multisection resonators for common-mode suppression. By properly designing the input/output (I/O) resonators associated with the filter composed of four bi-section resonators, a balanced filter with good common-mode suppression is realized, but its rejection bandwidth is rather limited. To widen the rejection bandwidth, the I/O bi-section resonators are replaced by the tri-section ones so that a balanced filter with good common-mode suppression and wide rejection bandwidth may be realized by suitably arranging the composed bi-/tri-section resonators. Specifically, a stopband-extended balanced filter with good common-mode suppression (>50 dB) within the differential-mode passband is implemented and its stopbands are also extended up to 5f₀ ^d with a rejection level of 30 dB, where f₀ ^d is the center frequency in differential-mode operation.     

Dielectric Resonator Filters for Application in Microwave Integrated Circuits

Design of bandpass filters for microwave integrated circuits (MICS) utilizing dielectric resonators is discussed. Synthesis methods for both Tschebycheff and Butterworth responses are derived. Experimental results with S- and X-band filters are presented, and the agreement between theory and experiments is shown to be fairly good. Limitations on this technique due to poor temperature stability are also discussed.     

Slow-wave bandpass filters using ring or stepped-impedance hairpinresonators

This paper proposes a new class of slow-wave bandpass filters that uses a microstrip line periodically loaded with microstrip ring or stepped-impedance hairpin resonators. The new slow-wave periodic structures utilize the parallel and series resonance characteristics of the resonators to construct a bandpass filter. Unlike conventional slow-wave filters, the proposed bandpass filters are designed to produce a narrow passband at the fundamental mode of the resonators. The new filters provide lower insertion loss than that of parallel- or cross-coupled ring and stepped-impedance hairpin bandpass filters. The calculated frequency responses of the filters agree well with experiments