Multi-mode multi-band bandpass filter using hexagonal patch resonator

Resonant performances of the hexagonal resonators are analysed, and new tri-mode tri-band bandpass filter which operates at 2.5/2.8, 5.2/5.5 and 7.9/8.5 GHz with insertion loss of no more than 1.3 dB is presented by using a single fractal hexagonal resonator. It shows with fractal-shaped defection in hexagonal patch, filter performance is greatly improved and dual and tri-band bandpass filters can be implemented. The tri-band designs are demonstrated by experiment. The new hexagonal filter has outstanding advantages of multiple-band operation, miniature size, simple and compact structure without resonator coupling gaps. All these features are quite useful for applications in RF circuits.     

基于树状分形结构的半模基片集成波导带通滤波器

提出了一种基于分形结构的半模基片集成波导(HMSIW)滤波器。该设计将树状分形结构蚀刻在HMSIW的上金属表面,通过在其高频端引入宽阻带来产生带通效应。这种基于树状分形的HMSIW带通滤波器结构,随着迭代次数的增加,其相对带宽基本保持不变(S11<-15dB),但其带通边缘频响斜度变陡,且带外抑制特性不断增强。仿真结果与实验结果基本吻合,较好地验证了设计的可行性和有效性。     

X 波段微带交叉耦合带通滤波器的设计

耦合谐振电路在微波滤波器的设计,尤其是在窄带滤波器的过程中起着非常重要的作用。本文采用 基于耦合系数和外部品质因数的耦合谐振电路滤波器的方法设计了X 波段的开环交叉耦合微带带通滤波器。由于 引入非相邻谐振器之间的交叉耦合,在滤波器的输入端口和输出端口之间有多个通路,这种多径结构能在有限频率 处产生多个传输零点,而且通过调整传输零点的位置,可以调整滤波器选择性和带内群时延性能。设计的滤波器在 介电常数为2. 2、厚度为0. 254mm 的RO5880 介质板上加工,测试结果显示,该滤波器具有结构简单紧凑、损耗低、选 择性高、带外抑制极佳的特点,具有较好的工程应用价值。     

Dual and tri-band bandpass filters based on novel Π-shaped resonator

A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.     

Tunable microstrip bandpass filter with constant fractional bandwidth based on cascade triplet topology

This paper presents an approach for designing 3-pole tunable microstrip bandpass filter with constant fractional bandwidth (CFBW). To achieve sharp roll-off responses, a cross-coupling scheme is adopted in the filter design. Cascade triplet (CT) topology and source-load coupling scheme are used to introduce three transmission zeros (TZs) in the design of 3-pole tunable filters. Thanks to tunable coupling coefficient K_c, the TZs allocated at the low-end of passbands can be tuned, which providing a reconfigurable selectivity. For the purpose of demonstration, the 3-pole tunable bandpass filters with CFBW are designed, fabricated, and measured. The proposed filter can be tuned over a wide fractional range up to 50%. The measured 3-pole filter shows a tuning range of 950–1460 MHz, with a fractional bandwidth (FBW) of 13.1% ± 2.5% and an insertion loss of 1.8–3.6 dB. Measured results of the filter present sharp roll-offs, which agree well with the simulated counterparts.     

低温共烧片式多层带通滤波器仿真优化及制备

采用AnsoftHFSS电磁场模拟仿真软件,对LTCC多层带通滤波器制备过程中的介质材料与工艺偏差进行模拟仿真,并与实际器件测试结果对比。研制的片式多层带通滤波器的偏差的允许范围是:微波介质陶瓷材料介电常数误差±2%,而品质因数由于本身较高,在一定范围内对滤波器的性能影响不大;工艺上应控制流延生瓷片厚度±1.5μm、叠层/切割误差±50μm,工艺中的分层缺陷则导致器件性能劣化,中心频率严重偏移。     

A microstrip wideband bandpass filter based on λ/2 stub with spurious passband suppression scheme

In the design of bandpass filters, the use of λ/2 stubs of shunt configuration had been mostly unacceptable due to their effect of narrow stopband bandwidths in the ensuing filters. The design of bandpass filter presented in this article introduces 360° series transmission line segments to increase the stopband bandwidths to an acceptable level without affecting the wide passband. This designed filter has low insertion loss of less than –1.98 dB and a fractional bandwidth of 50% at 6 GHz mid-band frequency. A sharp rejection in the stopband is observed. To further widen the bandwidth of stopbands, a series capacitor and a shunt stub are used. The transmission line model of the filter is in good agreement with measured results. The filter is planar and is fabricated on FR-4 substrate which makes it cost-effective and easy to fabricate.     

A design method of optical bandpass filters

A design method of optical bandpass filters which are composed of several resonators consisting of dielectric layers is discussed. The relation between the loaded Q of a resonator and the thickness of each layer is calculated by treating equivalently each layer as a segment of transmission line and represented on a chart. It becomes possible to design an arbitrary value of loaded Q by using the chart. Thus, an optical bandpass filter of required bandwidth and rejection characteristic can be designed by finding out the optimum thickness of each layer of the resonator which is the component of the filter     

Miniaturized dielectric waveguide filters

Design techniques for a new class of integrated monolithic high-permittivity ceramic waveguide filters are presented. These filters enable a size reduction of 50% compared to air-filled transverse electromagnetic filters with the same unloaded Q-factor. Designs for Chebyshev and asymmetric generalised Chebyshev filter and a diplexer are presented with experimental results for an 1800 MHz Chebyshev filter and a 1700 MHz generalised Chebyshev filter showing excellent agreement with theory.     

Dual-mode filters with conductor-loaded dielectric resonators

In this paper, a new class of dual-mode microwave filters is presented. These devices use conductor-loaded dielectric resonators with unloaded Q-factors of 2000-8000 achievable in half the physical size of TEM filters and with good spurious performance. The basic properties of this resonator have been examined with the aid of a finite-element field-analysis package. Fundamental design rules for bandpass filters have been developed. A design example of a transmit filter for a ground-signal-metal cellular-radio base station is demonstrated     

Optimisation of SIW bandpass filter with wide and sharp stopband using space mapping

This work presents a substrate integrated waveguide (SIW) bandpass filter with wide and precipitous stopband, which is different from filters with a direct input/output coupling structure. Higher modes in the SIW cavities are used to generate the finite transmission zeros for improved stopband performance. The design of SIW filters requires full wave electromagnetic simulation and extensive optimisation. If a full wave solver is used for optimisation, the design process is very time consuming. The space mapping (SM) approach has been called upon to alleviate this problem. In this case, the coarse model is optimised using an equivalent circuit model-based representation of the structure for fast computations. On the other hand, the verification of the design is completed with an accurate fine model full wave simulation. A fourth-order filter with a passband of 12.0–12.5 GHz is fabricated on a single layer Rogers RT/Duroid 5880 substrate. The return loss is better than 17.4 dB in the passband and the rejection is more than 40 dB in the stopband. The stopband is from 2 to 11 GHz and 13.5 to 17.3 GHz, demonstrating a wide bandwidth performance.     

Narrow-band microstrip bandpass filters with low radiation lossesfor millimeter-wave applications

Microstrip lines are attractive for the lower millimeter-wave ranges, but use of relatively thick substrates would be desirable in order to minimize losses. On such substrates the usual types of microstrip narrowband bandpass filters (formed from, e.g. coupled line segments with open ends) tend to radiate strongly giving very poor performance. It has been found that a grating technique initially developed for use with dielectric waveguides can be adapted for microstrips to obtain narrowband millimeter-wave microstrip filters with little radiation and strong filter characteristics. The stopbands are broad, the second passband occurring at three times the frequency of the first passband. These filters use parallel-coupled gratings with a single grating in cascade at each end. The modifications to the dielectric waveguide filter theory that are necessary for use with microstrips are detailed. Experimental results from microstrip realizations, which demonstrate their potential for millimeter-wave microstrip applications, are also presented     

Bandpass filters using dual-mode and quad-mode Mobius resonators

Compact bandpass filters are being developed using Mobius wire-loaded cavity resonators. Initial results on tuned filters indicate that excellent filter characteristics can be attained in devices that are significantly smaller than traditional wire-loaded cavity technologies. A novel quad-mode Mobius resonator is presented which occupies the same volume as a dual-mode Mobius resonator. A four-pole bandpass filter is demonstrated using a single quad-mode Mobius resonator. Precisely controlled dielectric loading of dual-mode Mobius wire resonators has been implemented to realize bandpass filters. Two-pole and four-pole bandpass filters are demonstrated using one and two dual-mode dielectric-loaded Mobius resonators, respectively     

Planar three-resonator bandpass filters with cross coupling

New designs of planar three-resonator bandpass filters with cross coupling having a large variety of frequency characteristics are considered. In addition to better one-sided selectivity, such filters implement symmetric amplitude–frequency characteristics with an attenuation pole at each side of the passband. These filters can also have constant delay time in the passband. Concatenation of the proposed three-resonator filters leads to multiresonator filters with high selectivity determined by two attenuation poles at each side of the passband. It is found that the type of connection of the middle resonator in the circuit of a three-resonator filter with cross coupling results in substantial differences in amplitude–frequency characteristics. The results of modeling of different frequency characteristics are presented. It is shown that filters have small dimensions, which are comparable to overall dimensions of microwave ceramic filters. For example, dimensions of a three-resonator stripline filter designed for a frequency of 1.9 GHz are 9.4 × 5 × 2 mm for the permittivity of the filter material ε_r = 92 and dimensions of a six-resonator filter are 10 × 9.4 × 2 mm.     

新型紧凑型带通滤波器的设计

文章设计了两个通带位于超宽带低频范围的带通滤波器,用一种T型结构来代替传统带通滤波器中的四分之一波长传输线,这种替代减小了滤波器的尺寸.而且,可以很方便的控制位于滤波器通带两端的传输零点,即合理的调节开路支线的电长度,进而可以方便的控制滤波器的通带范围.为了证明以上新型滤波器的优点,设计了两个开路支线电长度不同的带通滤...     

Design of Nonradiative Dielectric Waveguide Filters (Short Papers)

An efficient design technique of nonradiative dielectric waveguide filters for use at millimeter wavelengths is developed. Filter stuctures considered here are a gap-coupled type and an altenating-width type. According to present theory, 3-pole, 0.1-dB Chebyshev ripple bandpass filters with a 2-percent bandwidth at a center frequency of 49.5 GHz were designed and fabricated with Teflon dielectric. Calculated and measured filter responses agree quite well, and excess insertion losses are found to be as small as 0.3 dB for both types of the fabricated filter circuits.     

Microstrip bandpass filters on substrates with high permittivities

A new class of compact microstrip bandpass filters, the stepped-impedance resonators of which are located close together at a gap of 0.1–0.2 mm, is described. Basic two- and three-element sections of microstrip filters, which are designed around stepped-impedance impedance resonators used to implement tiny selective devices with overall sizes and characteristics comparable to those of microwave ceramic filters, are proposed. It is justified that the mentioned filters can be equipped with closely neighboring metallic shields whose heights are equal to the substrate thickness. As a consequence, these filters turn out to be thinner. The frequency responses of experimental microstrip filters operating at frequencies of 1.75–2 GHz and manufactured on the 1-mm-thick substrates with the permittivity ɛ _r = 100 have been analyzed. The three-pole microstrip filter with a shield (its operating frequency is 1.96 GHz, and sizes are 5 × 5 × 1.5 mm) has been simulated. It is demonstrated that new microstrip filters can be competitive with low-sized ceramic filters in certain applications.     

Bandpass and Pseudo-High-Pass Quasi-Optical Filters

Two forms of quasi-optical filters are discussed herein for use at millimeter-wave frequencies and possibly for far infrared frequencies. One form consists of metallic grids with intervening dielectric support material which forms a quasi-optical filter analogous to the inductively coupled waveguide bandpass filter. Because of dielectric losses, the relatively weak upper stopband, and the rapidly repeating passbands, this type of structure leaves much to be desired as a bandpass quasi-optical filter. However, when designed for wide bandwidth, it makes a very good pseudo-high-pass filter. For moderate- to wide-band bandpass applications, pseudo-high-pass filters of this type can be designed to match with a form of quasi-optical low-pass filter previously treated by the authors, in order to give a bandpass filter with strong, broad stopbands on both sides of the passband. Design principles, computed performance, and experimental results are presented for both pseudo-high-pass and bandpass structures.     

Direct-coupled microwave filters with single and dual stopbands

This paper presents new ideas for the design and implementation of microwave filters with single and dual stopbands. They can be realized with waveguide, coaxial, dielectric resonators, or in a planar technology. The new methods represent an advance over present methods in that the resonators are direct coupled, thus avoiding the need for transmission line phase lengths between resonator stubs that tend to degrade performance due to their dispersion and are difficult to adjust during tuning. Three bandstop (BS) configurations are presented. The first will accommodate even or odd characteristics and also asymmetric responses, although some negative or diagonal cross-couplings will be needed. The second resembles the cul-de-sac configuration for bandpass filters and needs no diagonal or negative couplings even for asymmetric characteristics. The third is an application of the cul-de-sac synthesis technique to dual-band bandstop (DBBS) filters. All these BS designs are very similar to regular bandpass filters in their design and realization. The design of a DBBS filter is presented and compared with an equivalent bandpass filter to demonstrate its advantages. Finally, the simulated and measured results of a fourth-degree BS filter design in the novel cul-de-sac configuration are presented.     

脊双模波导滤波器的分析及设计

介绍了一种能实现脊双模波导滤波器的新型结构,分析了其腔内模式的耦合极性,利用不同的耦合极性对频率响应的影响可实现具有一对传输零点的双模滤波器,也可实现无传输零点的双模滤波器.以相同脊谐振单元不同的放置方向组成的两种带通滤波器为例,利用AnsoftHFSS仿真得到了两种不同的频率响应,结果与理论分析一致.最后设计出了一个六阶三传输零点的双通带滤波器,带内插损均小于0.6 dB,回波损耗小于-15 dB.