Microstrip bandpass filters using coupled feed lines for third and fourth generation communications

In this paper, two compact tuneable bandpass filters (BPFs) based on the coupled feed lines are introduced. To approach a compact size, the coupled feed lines are bended. To design a high performance single-band bandpass filter (BPF), coupled feed lines are loaded by T-shaped stubs (as main resonators) and rectangular stubs (as suppressor stubs). Also, the mechanism of coupled feed lines combining with T-shaped open stubs is analyzed to show a tunable passband. The dual-band BPF includes two big radial-stubs, two small radial-stubs, two T-shaped structures and spiral coupled feed lines. The LC model of big radial-stubs is analyzed to compute the equation of transmission zero using its transfer function. The passband frequency of single-band BPF resonates at 2.12 GHz (3G) with corresponded insertion loss of 0.83 dB. Also, for dual-band BPF, the measured insertion-losses of first and second passbands are close to 0.8 and 1.1 dB, respectively. The frequency responses of BPFs are easily adjusted by altering the physical dimensions, demonstrating a adjustable performance. To verify the correct operation of circuits, the proffered filters are implemented and tested.     

Fractal Dual-Mode Open-Loop Quasi-Elliptic Bandpass Filter with Source-Load Coupling

To realize the feature of small size and high selectivity, a microstrip miniature fractal quasi-elliptic bandpass filter (BPF) with two transmission zeros (TZs) near each skirt is investigated in this paper. The TZs are created by source-load coupling between the input and output E-shaped feeding structures. By using a dual-mode Minkowski fractal shorted stub loaded open-loop resonator, the proposed BPF achieved a size reduction of 97.5% compared with the conventional square dual-mode loop BPF. Even mode analysis is adopted to characterize the Minkowski structure. The frequency responses of the current BPF were simulated and measured with good agreement.     

Coplanar Waveguide Bandpass Filters With Compact Size and Wide Spurious-Free Stopband Using Electromagnetic Bandgap Resonators

This work presents a novel coplanar waveguide (CPW) bandpass filter (BPF) that uses electromagnetic bandgap (EBG) resonators to reduce the size and suppress the harmonic responses. The propagation characteristic of the EBG structure is investigated by its associated equivalent circuit model. Compared with the conventional half-wavelength resonator at 5GHz, the EBG resonator is 60.5 % more compact. Based on the EBG CPW resonators, the inductively-coupled two-pole BPF with 3.8% 3-dB bandwidth and 2-dB insertion loss at 5GHz is implemented. This structure generates a 59.6% reduction in size and suppresses a second harmonic passband when compared with a conventional filter. To eliminate the third harmonic response, the proposed EBG CPW BPF further incorporates two EBG structures into its input and output ports and has the merit of a small circuit area     

准椭圆函数带通滤波器的一般设计方法

介绍了准椭圆函数滤波器的一般设计方法,并给出了一种用于S频段、具有非对称传输零点、3阶同轴线型带通滤波器的设计实例,使用部分分式展开法综合出M矩阵,给出仿真模型和仿真结果.测试结果表明,该滤波器具有低插损、高阻带抑制等特点,设计方法切实可行.     

Q-Band GaAs Bandpass Filter Designs for ALMA Band-1

We report on the design and experimental results of Q-band GaAs bandpass filters (BPFs) for the Atacama Large Millimeter/submillimeter Array (ALMA) band-1 receiver. The BPF is required to reject the lower side band from 15.3 to 29 GHz while retain minimum insertion loss across the passband of 31.3 to 45 GHz. In order to reduce the size and weight of receiver module effectively, on-chip BPF designs using the commercial GaAs process are proposed. The parallel-coupled BPF with quarter-wavelength resonators is adopted to achieve a wide fractional bandwidth of about 37%. In addition, the capacitive/inductive loaded coupled-line and the stepped-impedance resonator are used to largely reduce the filter size. Moreover, the cross-coupling effect is introduced to create transmission zeros, such that the required 25 dB stopband rejection below 29 GHz can be achieved. Specifically, two GaAs BPFs with sizes less than $1.24times 0.8 {rm mm}^{2}$ are demonstrated. They will be applied to the multi-chip-module version of ALMA band-1 receiver prototype for further system evaluation and feasibility studies.      

Broadband Cascade Quadruplet Bandpass Filter With Low-Temperature Co-Fired Ceramic Technology

The broadband bandpass filter (BPF) designed with low-temperature co-fired ceramic technology has been proposed in this letter. By adopting a quadruple resonator, the broadband BPF with compact size can be fabricated. A quadruple resonator with metal-insulator-metal capacitors is employed to make inductive and capacitive couplings. The coupling scheme can create two transmission zeros at both sides of passband skirts by appropriately selecting the coupling coefficient. The center frequency and bandwidth ratio of this filter are 3.875 GHz and 50%, respectively. This filter can increase the sensitivity and linearity in the wireless communication system as well     

Compact and high-performance bandpass filter and diplexer based on SCMRC-loaded SIR

Bandpass filter (BPF) and diplexer, which are required to be compact size and high performance, are widely used in modern wireless communication systems. In this article, novel BPF and diplexer are designed using the proposed resonator called spiral compact microstrip resonator cell (SCMRC)-loaded stepped-impedance resonator (SIR). The SCMRC-loaded SIR is proposed using the slow-wave structure SCMRC to replace the low-impedance section of the conventional SIR. Compared with the conventional SIR, the new SCMRC-loaded SIR has a compacter size and can generate a transmission zero above its fundamental resonant frequency. As examples, a BPF with the central frequency at f ₀?=?1?GHz and a diplexer operating at 0.9/1.57?GHz are designed and fabricated. The fabricated BPF occupies a compact size of 0.07 λ ₀?×?0.035 λ ₀ and has a??60?dB rejection level wide stopband from 1.2 f ₀ to 3.8 f ₀. The fabricated diplexer occupies a compact size of 0.076 λ ₀?×?0.128 λ ₀ and has an up to??50?dB output isolation. Good agreement can be observed between the simulations and the measurements.     

Compact Ultra-Wideband Conductor-Backed Coplanar Waveguide Bandpass Filter With a Dual Band-Notched Response

This work presents a novel ultra-wideband (UWB) bandpass filter (BPF) based on a conductor-backed coplanar waveguide structure with tunable transmission zeros. The symmetrical UWB BPF, which consists of the broadside-coupled transitions and the stub resonators in double-layer configuration, achieves a UWB bandwidth with transmission zeros. For characterizing this structure, the equivalent-circuit model is established to realize a four-pole response with two transmission zeros located close to the passband edges. To eliminate the interference of the coexisting wireless local area network (WLAN) within the UWB spectrum, two slotlines are symmetrically arranged on the ground plane of UWB BPF to generate the band-notched frequencies at 5.2 and 5.8 GHz simultaneously. The proposed UWB BPFs have the advantages of compact size, low insertion loss, good selectivity, and flat group delay. All results obtained from the equivalent-circuit model and the full-wave simulation are verified by measurements.      

（英）基于新型双模圆谐振腔的高选择性毫米波滤波器

提出了一种新颖的高选择性毫米波带通滤波器及其设计方法.在圆谐振腔的侧壁加入槽型微扰结构,通过调节微扰小槽的角度可以控制滤波器带外传输零点的位置,从而实现了带宽可调、高选择性的双模圆谐振腔带通滤波器.根据该滤波器结构、理论分析和仿真设计基础,研制了在V波段滤波器样品并进行了测试.实验结果与方正吻合得良好.与传统双模圆腔滤波器相比,所提出的滤波器不需要额外的调节结构,其设计方法简单,选择特性高,结构紧凑,具有一定的工程价值用于高性能平面化毫米波滤波器的设计.     

A new compact LTCC bandpass filter using negative coupling

This letter presents the design and realization of a new compact bandpass filter (BPF) fabricated on multilayered ceramic substrates. This BPF features coupled resonators with negative coupling coefficients. A BPF with center frequency 2.45 GHz is designed and fabricated. Its size is only 2.0 mm/spl times/1.8 mm/spl times/0.67 mm when implemented by a standard low temperature co-fired ceramic technology. The size reduction is due to the higher coupling coefficient between the negatively-coupled resonators than the positively-coupled ones, allowing tighter space between the resonators. The measured insertion losses of the previous BPF were less than 3dB and return losses more than 18dB in the passband. The measured result agrees very well with the electromagnetic (EM) designed response.     

Miniaturized Bandpass Filters With Double-Folded Substrate Integrated Waveguide Resonators in LTCC

This paper proposes miniaturized bandpass filters with double-folded substrate integrated waveguide (SIW) resonators using multilayer low-temperature co-fired ceramic (LTCC) technology. Formed by inserting a metal plate with two orthogonal slots into the cavity, the double-folded SIW resonator is used for the circuit size reduction with its footprint about a quarter of the conventional ${rm TE}_{101}$ mode. With LTCC technology, there is more flexibility to organize the cavities of filters because of the 3-D arrangement. The vertically stacked cavities are coupled by “L”- or “U”-shaped slots, and if arranged horizontally, by an inductive window on the common sidewall or a suspended stripline between the cavities. Through experimental measurements and simulations at both the $Ka$- $V$ -bands, it has been demonstrated that the proposed filter has compact sizes and good frequency responses. The area of the fully stacked Chebyshev filter has 88% size reduction in comparison with a three-pole planar waveguide filter, while the vertically stacked quasi-elliptic filter has 74% size reduction in comparison with a four-pole planar waveguide filter.      

一种新型周期结构双频带通滤波器

提出了一种新型的周期结构双频微带带通滤波器(BPF——Bandpass filter),该结构由刻蚀在补偿微带线微带两边的两个不同周期结构构成,在3.72GHz和6.01GHz频率范围内获得了两个通带,该滤波器具有低的插入损耗、紧凑的结构和好的选择性,仿真结果和实验结果符合较好。     

Compact Ultra-Wideband Bandpass Filters Using Composite Microstrip–Coplanar-Waveguide Structure

Compact ultra-wideband bandpass filters are proposed based on the composite microstrip–coplanar-waveguide (CPW) structure. In this study, the microstrip–CPW transitions and the CPW shorted stubs are adopted as quasi-lumped-circuit elements for realizing a three-pole high-pass filter prototype. By introducing a cross-coupled capacitance between input and output ports of this high-pass filter and suitably designing the transition stretch stubs, a compact three-pole ultra-wideband bandpass filter is implemented with two transmission zeros located close to the passband edges. To further improve the selectivity, two microstrip shorted stubs are added to implement a five-pole ultra-wideband bandpass filter with good out-of-band response. Being developed from the quasi-lumped elements, and not from the transmission lines, the proposed ultra-wideband filters have sizes more compact than those of the published wideband filters. The proposed ultra-wideband filters have the merits of compact size, flat group delay, good insertion/return loss, and good selectivity. Agreement between simulated and measured responses of these filters is demonstrated.     

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     

A novel compact interdigital bandpass filter using multilayer cross-coupled folded quarter-wavelength resonators

In this letter, a novel compact cross-coupled interdigital bandpass filter (BPF) is developed. By using multilayer folded quarter-wavelength resonators, the size of the filter is reduced greatly, meanwhile a cross-coupling is introduced to produce transmission zeros and thereby improve the stopband characteristics of the filter. As an example, a four-pole BPF centered at 2.25GHz with a fractional bandwidth of 31% is designed, fabricated, and measured. The simulated and measured results show an excellent agreement.     

Ku 波段微带交叉耦合带通滤波器的结构与设计

基于广义切比雪夫滤波器综合理论,本文设计了一个Ku 波段微带发夹谐振型交叉耦合滤波器。该滤波器的拓扑结构为CQ 型。由于引入非相邻谐振器之间的耦合,在有限频率点处产生传输零点,这样不仅使滤波器具有更好的选择性,而且其结构更加紧凑,尺寸也大大缩小。本文通过HFSS 电磁仿真软件对其进行了优化设计。其仿真结果很好地体现了该滤波器的特性。与同阶数的传统滤波器相比,交叉耦合型滤波器具有更好的带外抑制特性,有较好的工程应用意义。     

A compact and high performance dual-band bandpass filter based on unbalanced composite right/left-handed transmission lines for WLANs applications

In this paper, a novel compact microstrip dual-band (DB) bandpass filter with high selectivity for wireless local area networks applications is proposed. The design procedure is based on unbalanced composite right/left-handed (UCRLH) transmission lines (TLs). The DB features can be achieved by unbalancing the CRLH transmission line. The necessary conditions to obtain a discontinuous transition between the left- and right-handed bands, intended to provide UCRLLH TL, are investigated. The application of this technique to design of compact DB filters is illustrated. The structure of the proposed DB filter is implemented by a series interdigital capacitor located between two microstrip lines that shorted to the ground plane by vias. The vias with microstrip lines acting as a shunt connected inductor while the series capacitor is realized by interdigital capacitor. The design procedure based on a simple equivalent circuit is also introduced. The proposed filter has advantages such as compact size, easy fabrication, high selectivity, low insertion loss, high return loss and, design flexibility. To validate the proposed technique, the proposed DB filter has been fabricated and tested. Good agreement has been found between simulation and measurement results. The total size of the proposed UCRLH DB filter is 0.17 λ_g × 0.048 λ_g, where λ_g is the guided wavelength of the lower pass-band. The size of the proposed DB filter is more compact in comparison with known similar filters.     

Design and analysis of a super compact wide-band bandpass filter based on metamaterial resonators

In this paper, a novel compact wide-band bandpass filter (BPF) with a wide frequency range is presented. This filter consisting of a multi-mode resonator (MMR) and four metamaterial unit-cells benefits from a very compact size. Unit-cells based on a complementary spiral resonator (CSR) including a metallic via, improve both upper and lower stopband rejection and compensate the insertion loss (I.L) within the passband altogether. This wide-band filter presents a 3-dB bandwidth of 7.7 GHz, ranging from 3 GHz to 10.7 GHz and the Insertion loss is less than 0.7 dB over the passband. The measured results are in good agreement with both the full-wave electromagnetic simulation and the proposed circuit model results. The dimension of the fabricated filter is 0.128 λ × 0.1 λ (i.e., 5.6 × 4.4 mm²). This filter is considerably compact compared to the other wide-band bandpass filters with the same substrate.     

Compact multilayer dual-band bandpass filter design using stepped impedance resonators

Compact dual-band bandpass filter (BPF) for the 5th generation mobile communication technology (5G) radio frequency (RF) front-end applications was presented based on multilayer stepped impedance resonators (SIRs). The multilayer dual-band SIR BPF can achieve high selectivity and four transmission zeros (TZs) near the passband edges by the quarter-wavelength tri-section SIRs. The multilayer dual-band SIR BPF is fabricated on a 3-layer FR-4 substrate with a compact dimension of 5.5 mm ×5.0 mm ×1.2 mm. The measured two passbands of themultilayer dual-band SIR BPF are 3.3 GHz -3.5 GHz and 4.8 GHz -5.0 GHz with insertion loss (IL) less than 2 dB respectively. Both measured and simulated results suggest that it is a possible candidate for the application of 5G RF front-end at sub-6 GHz frequency band.     

Bandpass Filter with Wide Stopband Using Composite Right/Left Handed Transmission Line

Abstract This paper presents a wide-stopband bandpass filter (BPF) based on mixed coupling of the composite right/left handed transmission line (CRLH-TL). First the CRLH-TL resonator is introduced and analyzed. Then mixed coupling (Both electric coupling path and magnetic coupling path exist) of the novel resonator is explained. Based on the structural features of the CRLH-TL resonators, this coupling path can generate an additional transmission zero near passband without increasing the overall size of the filter. Then, good selectivity of the proposed BPF can be obtained. Meanwhile, in order to get a wide stopband, two open stubs are employed to suppress harmonic response of the CRLH-TL resonator. The filter is developed and analyzed based on microwave network theory and equivalent circuit method. The proposed BPF has been designed, fabricated, and measured. The measured results agree with the predicted ones closely.