一种新型介质栅波导滤波特性的研究

提出了一种新型介质栅波导阻带滤波结构,并采用多模网络与严格模匹配相结合的方法对该阻带滤波特性进行了仔细分析,给出了主模TM模的Brillouin图及滤波结构的归一化中心频率、阻带的宽度和带内最大衰减等特性和结构参数的关系.与传统的介质栅滤波器相比,新滤波器结构不仅具有金属损耗小的优点,而且其阻带带宽和带内衰减都要比传统介质栅滤波器的大得多.文中所给出的计算结果对设计该新型带阻滤波结构有指导意义.     

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     

Dual-Mode Dual-Band Bandpass Filter Using Stacked-Loop Structure

In this letter, a dual-mode dual-band bandpass filter using stacked-loop structure is proposed, which allows two transmission paths to radio frequency (RF) signals. Each of them using dual-mode resonators results in respective passband. This can provide convenience to easily change one passband frequency, while another keeps almost the same. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed bandpass filter. The theoretical and measured results are presented and show good agreement.     

A Quasi-Elliptic Function Dual-Band Bandpass Filter Stacking Spiral-Shaped CPW Defected Ground Structure and Back-Side Coupled Strip Lines

A quasi-elliptic function dual-band bandpass filter (BPF) stacking spiral-shaped coplanar waveguide defected ground structure and back-side coupled strip lines is proposed, which allow two transmission paths to radio frequency signals. Each of them has quasi-elliptic characteristics and results in a respective passband. This can provide convenience to change one passband operating frequency independently of the other one. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed BPF. Theoretical and experimental results with good agreement are presented     

Compact dual-band bandstop filter using folded resonator

A compact dual-band bandstop filter composed of main transmission line and four folded resonators is presented. Through analyzing the structure of folded resonator, it is found that the main transmission line connected with two proposed folded resonators exhibits the characteristic of band-rejection. Simulated results show that the center frequency of stopband is 2.72 GHz. Then, through adding another pair of folded resonator; a compact dual-band bandstop filter is achieved. Simulated results demonstrate that transmission poles are induced to have better selectivity. Additionally, in order to explain the mechanism of proposed structure, the LC equivalent circuit, analysis of parametric effect and surface current distributions are given. Due to the folded structure, the filter dimensions are reduced and the adjustable stopband is another feature. By virtue of optimization, proposed structure is fabricated. Measured results agree well with the simulation.     

Photonic bandpass filters with high skirt selectivity and stopband attenuation

A new photonic signal processor topology that simultaneously achieves both a high-Q and a high skirt selectivity and stopband attenuation filter response is presented. It is based on a novel dual-cavity bandpass optical structure in which two pairs of active fiber Bragg grating cavities are used with an optical gain offset to control the poles and stopband attenuation characteristics of the filter. This concept enables a large improvement in the filter stopband attenuation, rejection bandwidth, and skirt selectivity to be realized. Measured results demonstrate both a narrow bandpass bandwidth of 0.4% of center frequency and a skirt selectivity factor of 16.6 for 40 dB rejection, which corresponds to a 6.5-fold improvement in comparison to conventional single cavity high-Q structures. To our knowledge, this is the best skirt selectivity reported for a photonic bandpass filter to date. The new photonic filter structure has been experimentally verified and excellent agreement between measured and predicted responses is shown.     

A modified Chebyshev bandpass filter with attenuation poles in thestopband

This paper describes a design method of a modified Chebyshev bandpass filter with attenuation poles in the stopband. The insertion of attenuation poles into resonators in the authors' bandpass-filter design is accomplished by connecting a lumped inductor or capacitor in series with a shunt-type coaxial transmission-line resonator. The inserted poles which are distributed over the stopband can be chosen such that the insertion loss of the filter has equiripple characteristic and maximum attenuation in the stopband with the given number of attenuation poles. The modified Chebyshev bandpass filter designed by this method can be effectively used in diplexer design     

Compact Structure With Three Attenuation Poles for Improving Stopband Characteristics

A novel compact structure with three controllable finite attenuation poles at stopband is presented. The new structure is composed of a pair of symmetrical parallel coupled-lines and a capacitive load. With this configuration, three finite attenuation poles are available, which can improve the stopband characteristics of low-pass filters (LPFs) or the upper stopband performances of band-pass filters. The research method is based on a transmission-line model for tuning the finite attenuation poles. In order to examine the feasibility of the proposed structure, a new type of LPF with broad stopband and sharp cutoff frequency response is designed, fabricated, and measured. The experimental results of the fabricated circuit agree well with the simulation and analytical ones     

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.     

Wideband and compact bandstop filter structure using double-plane superposition

A novel bandstop filter (BSF) structure is proposed and measured for wideband and compact circuit applications. The proposed BSF realizes the wide stopband (2-octave) characteristics by superposing two different photonic bandgap (PBG) structures into a coupled double-plane configuration. Only three cells of the proposed structure are enough for the measured 10 dB stopband from 4.3 to 16.2 GHz. We expect this novel BSF structure is widely used for compact and wideband circuit applications, such as compact high-efficiency power amplifiers using harmonic tuning techniques.     

一种超宽阻带微带低通滤波器的设计

基于传统阶跃阻抗滤波器,提出了一种易于实现的超宽阻带微带低通滤波器改进设计方案。低阻抗线部分采用扇形微带结构,在同等阶数下,该结构的滤波器与传统阶跃阻抗滤波器相比,具有更紧凑的电路结构以及更好的阻带特性。在滤波器末端并联开路短截线,使得阻带增加额外传输陷波点来抑制寄生通带。利用ADS和HFSS仿真软件对滤波器结构进行优化设计,并进行了实物的加工和测试。实测结果表明,通带3 dB 截止频率为2 GHz,通带内0-1.8 GHz 回波损耗大于20 dB,3-20 GHz 频率范围内的阻带抑制能达到25 dB 以上。     

Novel coplanar-waveguide bandpass filters using loaded air-bridge enhanced capacitors and broadside-coupled transition structures for wideband spurious suppression

Novel inline coplanar-waveguide (CPW) bandpass filters composed of quarter-wavelength stepped-impedance resonators are proposed, using loaded air-bridge enhanced capacitors and broadside-coupled microstrip-to-CPW transition structures for both wideband spurious suppression and size miniaturization. First, by suitably designing the loaded capacitor implemented by enhancing the air bridges printed over the CPW structure and the resonator parameters, the lower order spurious passbands of the proposed filter may effectively be suppressed. Next, by adopting the broadside-coupled microstrip-to-CPW transitions as the fed structures to provide required input and output coupling capacitances and high attenuation level in the upper stopband, the filter with suppressed higher order spurious responses may be achieved. In this study, two second- and fourth-order inline bandpass filters with wide rejection band are implemented and thoughtfully examined. Specifically, the proposed second-order filter has its stopband extended up to 13.3f/sub 0/, where f/sub 0/ stands for the passband center frequency, and the fourth-order filter even possesses better stopband up to 19.04f/sub 0/ with a satisfactory rejection greater than 30 dB.     

基于新型带阻谐振单元的双频带阻滤波器设计

基于螺旋交指结构设计了一种新型的带阻谐振单元,并采用全波仿真软件对其进行分析。仿真结果表明,在此谐振单元中存在2个较窄的阻带,改变单元结构的尺寸可分别控制2个阻带的位置。在此基础上,采用2个单元级联的方式设计并加工了一款具有优越电磁性能的结构紧凑的双频带阻滤波器。采用矢量网络分析仪对所设计的滤波器进行测试,测试和仿真结果吻合较好,2个阻带的中心频率为3.30GHz和4.93GHz,对应的阻带带宽分别为3.23³.37GHz和4.733.37GHz和4.73⁵.10GHz,阻带边缘陡峭度大于90dB/GHz,所设计的带阻滤波器具有优越的性能。此外,该滤波器的有效尺寸为24.0mm×5.2mm,与传统带阻滤波器相比较,小型化优势明显。     

Highly selective bandpass filter based on substrate integrated waveguide

A novel highly selective six-pole elliptic filter based on a substrate integrated waveguide (SIW) is proposed for the first time. The filter is composed of two planar SIW extend doublets. The modular design approach based on cascading small building blocks is adopted to reduce the effect of manufacturing tolerance on the performance of the filter. The proposed filter can produce four finite transmission zeros, and has an excellent stopband rejection characteristic. Measured results are presented and compared with results simulated by a high frequency structure simulator. Good agreement between simulated and measured results is observed.     

新型的方形贴片双模微带带通滤波器

提出了一种新型的方形贴片双模微带带通滤波器。该滤波器结构有一个切角,并且在贴片中心处开了一个两臂等长的十字槽,采用正交直接馈电方式,并在每条馈线上引入了一节与谐振腔有一定耦合的开路短截线。该结构在上下阻带都产生衰减极点,馈线上引入的微带线有效地抑制了寄生通带,提高了阻带抑制特性。仿真结果表明,该滤波器在中心频率2.9 GHz处,回波损耗优于–30.9 dB,通带内最小插入损耗为–0.1 dB,与实测结果基本一致。     

Wide-stopband microstrip low-pass filter using modified semi-circle patch resonator

In this article, a compact microstrip low-pass filter with elliptic-function response is proposed. To achieve wide stopband, modified semi-circle patch resonator in series with semi-circle stepped impedance resonator is used. The proposed structure achieves a wide stopband and a high selectivity within a small circuit area. The proposed filter has 3-dB cutoff frequency at 1.71?GHz and 20?dB rejection at 2.1?GHz. The stopband with the attenuation level better than ?18.7?dB is from 2.08 up to 16?GHz, and consequently we have reached the high and wide rejection in stopband as well as compact size. The structure is simulated, fabricated and measured. The measured results are in good agreement with the simulated results.     

基于新型谐振器的超宽带带通滤波器

采用两个新型四阶阶梯阻抗谐振器设计出一种新型超宽带带通滤波器,四个1/4波长的耦合线被平行放置于输入输出端,起到增加耦合强度的作用,三个谐振频率被调整在超宽带带宽(3.1 GHz～10.6 GHz)内。通过优化后,该滤波器在通带内具有五个传输极点,频带宽度在3.6 GHz～10.5 GHz,通带内回波损耗优于15 dB,最小插入损耗为0.6 dB,满足超宽带的传输要求。仿真结果显示,文中设计的滤波器具有小型化、低插入损耗和较好的带外特性等优点。     

小型高带外抑制超宽带滤波器设计

为了提高滤波器的带外噪声抑制,并兼顾小型化,提出了一种新型超宽带滤波器设计。首先,利用分路电磁耦合结构在通带两侧实现了2个传输零点,通过调节中间金属片与螺旋缺陷地可实现对2个零点的单独调节,由此实现了高带外抑制,且有利于滤波器的小型化;然后,利用基片集成波导与周期性缺陷地结构,在进一步提高频率选择性的同时,实现了较好的阻带性能;最后,设计并加工了一款工作频率为8.1 GHz、带宽为67%的滤波器。结果表明,仿真与测试结果吻合良好,证明了该设计方法的可靠性。     

组合式非周期缺陷接地结构的滤波特性研究

提出了一种新型的具有双阻带特性的组合式非周期性缺陷接地结构(CNPDGS),利用时域有限差分法(FDTD)对其滤波特性进行了电磁仿真,研究了其结构尺寸变化对阻带特性的影响,研制了带宽可调节的双阻带滤波器,测量结果与仿真结果一致性很好,此结构的双阻带中心频率位置及它们之间的间隔随着结构参数的变化而变化,两阻带之间的间隔可从3.5GHz到12GHz.这种新型结构可有效地抑制信号中的低端和高端干扰,具有较好的带通滤波特性.     

Analytical design of a microstrip UWB BPF with sharp rejection

This paper presents a new Ultra-WideBand (UWB) BandPass Filter (BPF) using half-wavelength (??/2) Stepped-Impedance Stub-Loaded Resonator (SISLR). Analytical equations derived by the even-odd mode analysis show the new filter has two tunable transmission zeros at both sides of the passband to provide a sharp rejection and seven transmission poles inside the passband to achieve U.S. UWB performance. For verification, a UWB BPF is designed, fabricated and measured. The measured results show that the fabricated filter has a -3 dB fractional bandwidth from 3.0 GHz to 10.9 GHz and its insertion loss less than 0.9 dB over the whole passband. Furthermore, the new filter exhibits a simple topology, sharp rejection, and deep stopband suppression.