Design and analysis of a structure-based microstrip bandpass filter

A structure-based microstrip passband filter with the center frequency of 2.6 GHz was put forward by using double-mode resonator based on defected ground structure （DGS） technology. A double-mode coupling resonator combined with DGS structure was used to achieve the resonance frequency and the filter size. CST microwave studio was used to optimize the attenuation performance to get the filter parameters. A structure-based passband filter was fabricated. Simulation is consistent with the measurement. Performance shows that the proposed filter could be suitable for the time division-long term devolution （TD-LTE） microwave systems at 2.6 GHz.     

Miniaturized microstrip lowpass filter with wide stopband using double equilateral U-shaped defected ground structure

A compact double equilateral U-shaped defected ground structure (DGS) unit is proposed. In contrast to a single finite attenuation pole characteristic offered by the conventional dumbbell DGS, the proposed DGS unit provides dual finite attenuation poles that can be independently controlled by the DGS lengths. A 2.4-GHz microstrip lowpass filter using five cascaded double U-shaped DGS units is designed and compared with conventional DGS lowpass filters. This low pass filter achieves a wide stopband with overall 30-dB attenuation up-to10 GHz and more than 42% size diminution.     

Quasi-elliptic filter characteristics of an asymmetric defected ground structure

An asymmetric defected ground structure (DGS) with respect to a microstrip line is proposed. Its unit cell consists of two square slots connected with a rectangular slot by meandered transverse slots. The simulated, measured and equivalent circuit responses have been presented. The unit DGS pattern under microstrip line produces wide rejection bandwidth and high sharpness factor. Its elliptic band-reject filter response is modelled by appropriate LC equivalent circuit. Two such DGS cells under a microstrip line produce 3-pole quasi-elliptic bandstop filter response, which shows deeper attenuation without appreciable change in pole frequencies in comparison to single cell structure. Unit DGS pattern under coupled gap microstrip lines produces band-accept filtering characteristics. The frequency characteristics show a quasi-elliptic highpass filtering characteristics with sharp lower transition knee. Accordingly, an LC equivalent circuit is proposed. A cascaded band-accept and band-reject filter is proposed for designing a wideband bandpass filter. The bandwidth and centre frequency of the bandpass filter can be varied by choosing different set of DGS dimensions.     

A design of the novel coupled-line bandpass filter using defectedground structure with wide stopband performance

In this paper, a novel three-pole coupled-line bandpass filter with a microstrip configuration is presented. Presented bandpass filters use defected ground structure (DGS) sections to simultaneously realize a resonator and an inverter. The proposed coupled-line bandpass filter provides compact size with low insertion-loss characteristic. Furthermore, a DGS shape for a microstrip line is newly proposed. The proposed DGS unit structure has a resonance characteristic in some frequency band. The proposed coupled-line filter can provide attenuation poles for wide stopband characteristic due to resonance characteristic of DGS. The equivalent circuit for the proposed DGS unit section is described. The equivalent-circuit parameters for DGS are extracted by using a three-dimensional finite-element-method calculation and simple circuit analysis method. A design method for the proposed coupled-line filter is derived based on coupled-line filter theory and the equivalent circuit of the DGS. The experimental results show excellent agreements with theoretical simulation results     

An asymmetric defected ground structure with elliptical response and its application as a lowpass filter

A new asymmetric defected ground structure (DGS) consisting of two square headed slots connected with a rectangular slot transversely under a microstrip line is proposed. In the frequency characteristics of its unit cell, an attenuation zero is observed close to the attenuation pole. The DGS unit is represented by Cauer's T-network, modeled by a third order elliptical lowpass filter and finally equivalent L-C parameters are extracted. Several studies have been accomplished on the influence of the geometric modification of the filter on its characteristics. Better transition sharpness, lower passband insertion loss and broader stopband are observed, compared to popular dumbbell DGSs due to its additional attenuation zero. The two-cell configuration of this DGS produces a three-pole lowpass filter having wide and deep stopband at low cutoff frequency. This is applied under the input and output feed lines of a parallel-coupled bandpass filter for suppressing harmonic frequencies. A lowpass filter is realized using cascaded investigated DGS and dumbbell DGS under a microstrip line.     

低辐射DGS 及其串扰分析

在传统哑铃形缺陷接地结构(DGS)的基础上,设计出一种新型低辐射DGS。该结构既具有传统DGS的优良电路性能,又大大降低了由于接地面蚀刻缺陷图案而引起的无意辐射。进一步仿真分析了低辐射DGS 的串扰,结果表明低辐射DGS 近端串扰峰值电压较哑铃形DGS 下降60%,远端串扰峰值电压下降了36. 8%,证明低辐射DGS 能大大降低由于DGS 的应用对周围电路产生的影响。与接地面完整的平行微带线相比,低辐射DGS 近端串扰略大,但远端串扰在4 ~6 GHz 频段内存在阻带,当受扰线工作在远端串扰的阻带频段内,对远端串扰的抑制效果十分明显。     

基于缺陷地结构的小型化双频带带通滤波器

提出了一种新型的基于缺陷地结构的双频带带通微带滤波器.缺陷地结构采用双模开口谐振环形式, 并使用不同组合方式的双模开口谐振环产生两个通带.滤波器的两个工作中心频率分别为3.5 GHz和5.8 GHz, 其中第一个频带涵盖了所有全球微波互联接入的应用频段, 第二个频带可以应用于雷达设备.为了进一步证实这款滤波器的性能, 基于Roggers RT5880板材制作了滤波器实物, 整体滤波器的大小仅为20 mm×20 mm, 测量数据和仿真结果吻合较好, 并且有两个传输零点, 可以满足工程上的需要.     

Compact stub type microstrip bandpass filter using defected ground plane

Usually a defected ground plane structure (DGS) provides only a band-reject response. However, in this work we introduce a simple band-accept circuit element in the DGS and developed a microstrip stub type compact 3-pole bandpass filter (BPF) at 4.2 GHz. The BPF has bandwidth and insertion loss 38% and 0.6 dB respectively. It has better than 25 dB rejection in the stopband up to 12 GHz.     

基于缺陷地抑制高阶谐波的带通滤波器设计

采用微带线设计的平行耦合滤波器(MCL-BPF)在通带以外往往产生谐波,出现寄生频段。利用缺陷地结构(Defected Ground Structure,DGS)的单极点带阻特性和慢波效应可以改善寄生通带,抑制谐波输出。对2.4GHz的传统微带平行耦合滤波器和改进型带通滤波器进行了仿真设计与加工测试。实测结果与仿真数据良好吻合,所提出基于斜哑铃型DGS的带通滤波器(S-DGS-BPF)可抑制至四阶谐波,抑制度达到-22dB以下,阻带为3-10GHz,中心频率处回波损耗为-26.93dB。并且改进型滤波器的尺寸缩小了约10%。     

Design of 10 dB 90° branch line coupler using microstrip linewith defected ground structure

The authors present a 10 dB 90° branch line coupler operating at 1.8 GHz and having a defected ground structure (DGS), a type of periodic structure realised by etching on the ground plane under the microstrip line. Owing to the additional effective inductance of the DGS, the characteristic impedance of the microstrip line is increased for the same width of conductor. A microstrip line of 150 Ω of characteristic impedance with 1 mm conductor width is realised by adding the DGS, while 1 mm corresponds to 82 Ω of conventional microstrip line on the RT/Duroid 5880 substrate with 2.2 dielectric constant and 31 mils of thickness. It is shown that a 90° branch-line 10 dB coupler can be fabricated using the 150 Ω line with DGS. Its measured performances are in good agreement with the predicted results     

Design of low-pass filter with 3-interations Koch fractal Pi-shaped DGS

A novel asymmetrical Pi-shaped defected ground structure (DGS) with 3-interations Koch fractal curves is proposed to design a microstrip low-pass filter (LPF) with ultra-wide stop-band (SB). The proposed LPFs with a single resonator and two cascaded resonators are both designed, simulated, manufactured and measured. Simulation and experiment results demonstrate that the designed LPF has a very sharp transition band (TB) and an ultra-wide SB performance compared with the existed similar symmetrical and asymmetrical DGS. The proposed LPF with two cascaded resonators is with a compact size of 36.8 mm×24.0 mm, a very low insertion loss of less than 0.7 dB under 1.9 GHz, and a wide SB from 2.2 GHz to 8 GHz with rejection of larger than 30 dB.     

High isolation dual-polarized patch antenna using integrated defected ground structure

This letter presents a high isolation dual-frequency orthogonally polarized rectangular patch antenna utilizing microstrip feed line integrated with a defected ground structure (DGS). The demonstrated approach results in a significant improvement in port isolation in comparison to a conventional dual-polarized antenna fed by simple microstrip lines. Measurements show an improvement of 20 dB in port isolation relative to the conventional antenna, operating at 2 and 2.5 GHz. Image impedance of a microstrip line with DGS is controlled by the DGS geometry without modifying the dimension of the line. A 150 /spl Omega/ high impedance line is effectively implemented using a microstrip line with 75 /spl Omega/ line width by incorporating the DGS.     

一种新颖羊角形缺陷地结构宽带带通滤波器

为了得到小型化的带通滤波器,该文提出了一种新的羊角形缺陷地结构(DGS),并将其与耦合开路枝节线结合,设计并制作了一种新型宽带带通滤波器。该带通滤波器的中心频率为7.95GHz,3dB通带为5.25~10.65GHz,相对带宽达到了68%。与以往的宽带带通滤波器相比,它具有结构简单,尺寸小的特点,仿真和测量结果吻合较好。     

基于缺陷地面结构和补偿微带线的低通滤波器

提出了一种新型一维周期缺陷地面结构（DGS）单元。文中给出了3个不同尺寸单元的5参数变化曲线,并使用DGS单元进行级联,形成一种补偿微带线。设计了一个低通滤波器,计算和测试结果显示该结构单元的截止频率由结构单元的物理尺寸决定,单元级联形成的多级低通滤波器具有良好的带通、带阻和谐波抑制特性。     

Design of a wideband common-mode filter using approximate closed-loop pattern of compact C-shaped defected ground structure

A compact common-mode filter is proposed to suppress common-mode noise for application of high-speed differential signal traces. The filter adopts one big C-shaped defected ground structure (DGS) cell in the left of ground plane and two small C-shaped DGS cells with opposite direction in the right of ground plane. Because these DGS cells have different dimensions, the filter has three adjacent equivalent resonant points, which can suppress wideband common-mode noise effectively. The left C-shaped DGS and its adjacent C-shaped DGS cell form an approximate closed structure, which can efficiently reduce the influence of the mutual capacitance. The filter provides a common-mode suppression from 3.6 GHz to 14.4 GHz over 15 dB while it has a small size of 10 mm10 mm. The fractional bandwidth of the filter is 120%, and the differential signals still keep good signal integrity. The experimental results are in good agreement with the simulated results.     

A novel defected ground structure for planar circuits

A new compact defected ground structure (DGS) is proposed for the microstrip line. The structure is compact in microstrip line direction. Here, this DGS is used to design a compact low pass filter (LPF) that is at least 26.3% more compact lengthwise than other reported compact structures and has sharper transition knee.     

基于DGS和SIR单元的超宽阻带低通滤波器设计

为了解决传统的微带线低通滤波器尺寸偏大,阻带较窄的问题,采用阶梯阻抗谐振(SIR)单元加载哑铃型缺陷地结构(DGS)单元设计了一个五阶微带低通滤波器,并通过在主传输线两侧添加并联开路枝节,以补偿DGS微带线的特性阻抗。测试结果表明:该滤波器结构尺寸21.6mm×8mm,3dB截止频率4GHz,通带内平均驻波比小于1.5,阻带范围5GHz～35GHz。实现了滤波器结构尺寸的减小和超宽阻带。     

Dual-band UWB bandpass filter with triangular DB-DGS for WLAN applications in DSRC band

A dual-band Ultra-wideband (UWB) bandpass microstrip filter with triangular dumbbell shaped defected ground structure (DB-DGS) for wireless local area network applications in DSRC band is proposed in this article. The proposed dual-band filter has center frequencies at 2.67 GHz and 4.68 GHz, return loss obtained is −33.40 dB and −16.55 dB respectively, wide bandwidth of 1.21 GHz (26%), pass band between 2.14 GHz and 6.44 GHz and high gain of 10.30 dB which makes it suitable for modern applications in dedicated short range communication operating in 5.8 GHz band. To further validate the design concept, a microstrip UWB filter is designed, fabricated and tested. Comparison is made among circular, square and triangular dumbbell shaped DGS on the basis of scattering parameters and bandwidth, in which triangular shaped DB-DGS outperforms the other two. Further, parametric analysis of triangular DB-DGS has been performed and comparison is made with filters of similar nature. Experimental results are in good agreement with simulations. The fabricated filter is compact in size, has low insertion loss, exhibits high selectivity and demonstrates excellent out of-band performance.     

一种SLR结构陷波宽带滤波器的设计

在枝节加载谐振器（Stub-loaded Resonator,SLR）的理论基础上设计了一种陷波宽带滤波器,应用于3.0~6.7 GHz频段。该滤波器由一个倒T形短路枝节加载谐振器（Short SLR,SSLR）和一个基于半波长SIR基本结构的阶跃阻抗枝节加载谐振器（Stepped Impedance SLR,SISLR）构成。与传统陷波滤波器相比,该滤波器没有采用传统的缺陷地结构或缺陷微带结构,其陷波特性由SISLR与SSLR耦合所致,能够实现更好的设计灵活性。对电路进行了仿真和实物制作,仿真结果表明,插入损耗和回波损耗分别优于0.3 dB和12.2 dB,陷波的中心频率位于5.8 GHz,其分数带宽为6.8%。测试结果与仿真结果基本一致,体现了良好的电路性能。     

一种新颖的蝴蝶结形缺陷接地结构微带线

提出一种新颖的蝴蝶结形缺陷接地结构(DGS)微带线,分析了该微带线的带阻特性和慢波特性,同时考虑微带线损耗,建立了该微带线的等效电路模型及其参数提取,并分析了蝴蝶结形DGS结构变化对阻带特性的影响,最后将该DGS结构应用于紧凑结构低通滤波器的设计,模拟结果与实验结果吻合较好,验证了所提结构的可靠性。