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.     

Ultra-wideband bandpass filter using CPW-to-microstrip coupling structure

A novel ultra-wideband bandpass filter based on a back-to-back microstrip-CPW transition structure is presented. The filter is composed of two microstrip-CPW transitions and a section of microstrip line used as a multiple-mode resonator. The filter has been investigated numerically and experimentally. Both simulated and measured results show that the filter has a good performance, including a small insertion loss, a group delay variation of less than 0.2 ns, stopband of up to 16.0 GHz at high frequencies, and an out-of-band rejection level of below -20.0 dB.     

Ultra-wideband bandpass filter with hybrid microstrip/CPW structure

A novel ultra-wideband (UWB) bandpass filter (BPF) is presented using the hybrid microstrip and coplanar waveguide (CPW) structure. A CPW nonuniform resonator or multiple-mode resonator (MMR) is constructed to produce its first three resonant modes occurring around the lower end, center, and higher end of the UWB band. Then, a microstrip/CPW surface-to-surface coupled line is formed and modeled to allocate the enhanced coupling peak around the center of this UWB band, i.e., 6.85GHz. As such, a five-pole UWB BPF is built up and realized with the passband covering the entire UWB band (3.1-10.6GHz). A predicted frequency response is finally verified by the experiment. In addition, the designed UWB filter, with a single resonator, only occupies one full-wavelength in length or 16.9mm.     

Ultra-wideband bandpass filter using back-to-back microstrip-to-CPW transition structure

A novel ultra-wideband bandpass filter is proposed on a back-to-back microstrip-to-CPW transition structure. A multiple-mode resonator on a CPW is formed to allocate its first three resonant modes around the lower-end, centre and upper-end of the 3.1 to 10.6 GHz UWB passband. Its two sides are fed by two microstrip-to-CPW transitions with enhanced frequency-dispersive coupling degree. The designed filter exhibits good UWB passband behaviour with insertion loss <0.5 dB and group delay variation <0.35 ns.     

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.     

A compact planar ultra-wideband bandpass filter with multiple resonant and defected ground structure

A compact bandpass filter with dumbbell shape Defected Ground Structure (DGS) operating on ultra wide pass band (UWB – 3.1 to 10.6 GHz) is proposed. It is based on hybrid microstrip coplanar waveguide (dual sided metal) structure. A Multiple Resonant Structure (MRS) is constructed using coplanar waveguide (CPW) planar transmission line. The MRS makes the resonance using quarter wavelength and half wavelength open-ended CPW. The equispaced three resonances at lower (3.1 GHz), center (6.85 GHz) and higher edge (10.6 GHz) of the whole Ultra Wide Band is achieved using CPW MRS. To make the band as flat as possible, two more resonances are introduced using quarter wavelength microstrip patches on top of the commonly shared substrate, so the proposed filter becomes a five pole bandpass filter. A dumbbell shaped defected ground structure on either side of CPW MRS improves the return loss almost less than 20 dB over the whole UWB passband. The simulated results of proposed filter show good transmission response within passband and good rejection in out of the band. The simulated and measured results are very close to each other which proves the efficacy of proposed design.     

Ultra-wideband bandpass filter using back-to-back CBCPW-to-CBCPW transition

A new ultra-wideband bandpass filter using a back-to-back CBCPW-to-CBCPW transition structure is presented. The filter is composed of two CBCPW-to-CBCPW transitions and a section of a CBCPW line section used as a multiple-mode resonator. Using this transition, a new ultra-wideband filter prototype was designed, fabricated and measured. Obtained results show that the proposed filter can easily cover the band from 3.1 to 10.6 GHz.     

Dual-band bandpass filter based on mixed electric and magnetic coupling of the hybrid quasi-lumped resonator

A novel compact dual-band bandpass filter based on mixed coupling of the hybrid quasi-lumped resonator is proposed. The filter is composed of two independent signal paths, each can generate one passband with two identical hybrid quasi-lumped resonators. The proposal combines the mixed electric and magnetic coupling technology with this novel resonator in the filter design. Analysis of the filter has been done with the equivalent circuit method. To validate the approach, a dual-band bandpass filter operating at 2.4/5.2 GHz has been fabricated. Both passbands were realised with mixed coupling. An additional transmission zero is generated at either passband. Final fabricated filter has good band skirt, low insertion loss and good out-of-band performance. Reasonable agreement is found between the calculated, simulated and measured results. The implementation area is 0.21λ_g × 0.12λ_g.     

折线形哑铃缺陷地结构与微波滤波器设计

提出一种新型的折线形哑铃缺陷地结构(FDGS)。该FDGS对普通哑铃形DGS进行了改进,加入折线结构,从而在不增加蚀刻面积的情况下,大大增加其等效并联电容,获得较低的谐振频率。仿真结果显示,当某一特定尺寸的普通DGS的谐振频率位于4.7GHz时,同样大小的FDGS的谐振频率只有2.25GHz。制作了一个由三个相同的FDGS级联构成的带阻滤波器。结果表明:该带阻滤波器在1.8~2.78GHz之间,对信号的抑制从-26dB到-41dB。     

Reduction of mutual coupling between closely-packed antenna elements using defected ground structure

A simple ground plane structure that can reduce mutual coupling between closely-packed antenna elements is proposed. The structure consists of a dumb-bell-like pattern etched in a single ground plane. It is found that isolation of more than -40-dB can be achieved between two parallel individual planar inverted F antennas sharing a common ground plane. Influence of the designed defected ground plane structure on the radiation pattern is also investigated.     

Size reduction and harmonic suppression of rat-race hybrid coupler using defected ground structure

In this letter, a defected ground structure (DGS) is applied to design a compact microstrip rat-race hybrid coupler. The proposed structure can achieve both a significant reduction of size and harmonic signal. By embedding the DGS section, it is observed that the resonant frequency of the hybrid coupler is significantly lowered, which can lead to a large amount of size reduction for a fixed frequency operation. Besides, the third harmonic signal is suppressed to -30 dB with respect to a conventional rat-race hybrid coupler. In this case, the measured insertion loss is comparable to that of a conventional hybrid coupler.     

一种新颖的开口环地面缺陷结构低通滤波器

提出了一种新颖的具有陡峭边带和宽阻带的小型化低通滤波器.通过把开口谐振环地面缺陷结构(Split-Ring Resonator Defected Ground Structure,SRR DGS)与阶梯阻抗梳状谐振器结合,提高了滤波器的选择特性,同时获得了宽阻带.对所提出的结构作了加工并进行了实物测量,测试结果表明:滤波器选择特性大于160 dB/GHz,在2.98 GHz到8.2 GHz范围内抑制度大于20 dB,而占用面积仅为20×25 mm~2.     

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.     

Ultra-wideband bandpass filter on aperture-backed microstrip line

A novel ultra-wideband (UWB) bandpass filter is proposed on an aperture-backed microstrip line. With an aperture on the ground, a non-uniform resonator is constructed with the first three resonant modes occurring within the UWB band while the parallel coupling between resonator and feeders is largely enhanced. The designed filter exhibits good UWB passband behaviour with insertion loss <1.0 dB and group delay variation <0.25 ns.     

带DGS结构的宽带微带线准椭圆函数滤波器设计

准椭圆滤波器体积小，重量轻，结构紧凑，比契比雪夫滤波器有更好的过渡特性，更高的带外抑制，在卫星通信和移动通信中有广泛的应用前景。但在用准椭圆滤波器实现宽带滤波器时，有时会遇到耦合间隙过小难以加工的问题。在准椭圆滤波器的谐振器底板加入缺陷接地结构（DGS），可以增强谐振器之间的耦合。应用DGS结构，用较宽的耦合间隙实现较强的耦合，从而使宽带滤波器物理上更容易实现。应用三维电磁场仿真软件，设计了一种带DGS结构的宽带微带线准椭圆函数滤波器。     

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.     

Microstrip dual-band bandstop filter of defected ground structure and stepped impedance resonators

This article presents a compact microstrip dual-band bandstop filter (BSF), in which one λ_g/4 defected ground structure (DGS) pair is utilised to realise one stopband while two stepped impedance resonators (SIRs) help obtain another stopband and suppress the spurious harmonics. The design strategies and the equivalent circuits are introduced in detail. The measured results indicate 43.8% and 18.7% fractional bandwidth in the two stopbands (2.4 GHZ and 5.2 GHz) respectively, and the return loss is greater than 15 dB in the whole passband. In addition, size reduction can be conveniently achieved by adjusting the length of the SIRs and DGS.     

基于缺陷地结构的新型共面波导低通滤波器

提出了一种结构较独特的共面波导低通滤波器。为了减小通带内波纹、提高高频阻带抑制,叉指电容周期性加载共面波导结构被调整为非周期性结构,同时在共面波导的接地面上蚀刻了长方形缺陷地结构。基于上述方案设计制作了低通滤波器原形器件。仿真和测试结果表明:该滤波器的带外抑制至少增加了15.00dB,带内波纹显著变小(<1.25dB),通带内最大传输损耗为1.10dB。     

基于SGS的UWB滤波器设计

在传统哑铃型缺陷接地结构(defected ground structure,DGS)的基础上,提出了一种分割地结构(split ground structure),通过在传统哑铃型DGS上添加一条缝,形成了SGS结构,不仅有低通特性,而且产生了高通特性,即具有带通特性。借助于HFSS软件,比较了传统哑铃型DGS与SGS的仿真结果,分析了SGS结构参数变化对其频率特性的影响。并以此为基础设计了一种新颖的超宽带(UWB)带通滤波器,中心频率6.85 GHz,相对带宽110%,上边带20 dB阻带抑制达20 GHz。仿真结果表明,该滤波器具有较好的频率特性,说明基于SGS的UWB带通滤波器设计的有效性和可行性。     

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.