A History of Microwave Filter Research, Design, and Development

An account of the development of microwave filters is surveyed, commencing from 1937. Much of the foundation of modem filter theory and practice took place during the period of World War II and the years immediately following, especially by such pioneers as the late P. I. Richards, whose subsequent career is briefly described. Filter topics discussed include low-pass, bandpass, high-pass, and multiplexers constructed in a variety of media such as waveguide, coaxial line, microstrip, and stripline, as well as dielectric resonators. All types of filter characteristics are surveyed, such as Chebyshev, elliptic and pseudo-elliptic function, Achieser-Zolotarev, and a variety of generalized designs, including linear phase.     

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。     

Pseudo-elliptic microstrip line filters with zero-shifting properties

The paper presents a new design of pseudo-elliptic microstrip line filters. These filters employ a coupling scheme which allows shifting of transmission zeros from one side of the passband to the other by only changing the resonant frequencies of the resonators. To demonstrate the performance of these filters, a fourth-order bandpass filter with one transmission zero in the upper stopband is first designed. A second filter with a transmission zero in the lower stopband is then designed by simply adjusting the lengths of the resonators followed by minor optimization to account for the fact that the resonant frequencies can not be changed without slightly affecting the coupling coefficients in the used layout. Measured and simulated results are presented.     

Multiple-coupled microstrip hairpin-resonator filter

This letter presents the design of six-resonator multiple-coupled microstrip filter. A low-pass prototype of six-resonator multiple-coupled filter is developed first based on the conventional Chebyshev filter. The characteristics of attenuation poles located on both sides of the frequency response are described. According to the low-pass prototype, the design of a six-resonator multiple-coupled microstrip hairpin filter at 6 GHz is completed with the aid of EM simulation. The experimental results are demonstrated and discussed.     

通带耦合特性独立可调的双频微带滤波器设计

引入一种新型双通带滤波器耦合结构,采用微带线型SIR结构分别设计了切比雪夫型和准椭圆函数型2.4GHz/5.2GHz双频带通滤波器。运用电磁数值分析软件讨论了结构参数对双通带滤波器耦合性能的影响,以及准椭圆函数型滤波器耦合结构参数对其传输零点位置的影响,并在文中给出其变化规律。基于该耦合结构的新型双频带滤波器,设计自由度更高,两个通带所需耦合系数可以独立调节。根据以上结构参数所制备的样品,其性能测试结果与仿真结果吻合良好。     

基于平衡技术的微带低通滤波器版图优化设计

微带线结构的不连续性,使反射损耗和插入损耗较大,影响滤波器性能。利用平衡法提升滤波器并联分支中较低的特性阻抗,达到降低微带线宽度的目的,从而均衡整个滤波器的宽度,使版图仿真优化。以一个5阶切比雪夫微带低通滤波器设计为例,仿真结果表明,滤波器通带内反射损耗从-9.566dB降低到-15.837dB,插入损耗从0.679dB降低到0.322dB,与直接采用Richards变换和Kuroda规则设计微带低通滤波器相比,该方法能缩短滤波器设计周期,获得满意的滤波器性能。     

一种新颖的PBG宽阻带低通滤波器

 本文首次提出综合PBG结构和微带线结构两因素,来设计滤波器的概念.与普通PBG结构滤波器不同的是,本文采用具有T形和十字形短截线的微带线代替直线微带线,在接地板上只需刻蚀一列PBG结构即可构成宽阻带低通滤波器.文中以T形短截线PBG结构的低通滤波器为例,运用时域有限差分法(FDTD),分析了在不同短截线长度和PBG结构方孔边长的情况下,该滤波器的传输特性.文中还给出了该滤波器和Rumsey方法与Kim方法设计的级联、并联两种PBG结构低通滤波器的传输特性的模拟结果及其对比分析.最后,文中给出了模拟结果和测试结果,来验证所设计的低通滤波器的有效性.     

Synthèse et réalisation de filtres hyperfréquences à cavités bimodes ayant une réponse en fréquence dissymétrique

This article presents the study and the realization of microwave filters with asymmetric frequency characteristics using dual-mode cylindrical cavities. The synthesis method of such characteristics using generalized Chebyshev transfer functions is described. These functions allow the realization of symmetrically or asymmetrically prescribed transmission zeros. The method consists in synthetizing a generalized low-pass filter, in order to calculate the coupling matrix, the dual-mode structure has to realize. Concerning the practical design of the filter, a method is described for the realization of asymmetric characteristics with dual-mode cavities. Several measured characteristics of different laboratory models are presented.     

Design of Dual- and Triple-Passband Filters Using Alternately Cascaded Multiband Resonators

A novel method for designing multiband bandpass filters has been proposed in this paper. Coupling structures with both Chebyshev and quasi-elliptic frequency responses are presented to achieve dual- and triple-band characteristics without a significant increase in circuit size. The design concept is to add some extra coupled resonator sections in a single-circuit filter to increase the degrees of freedom in extracting coupling coefficients of a multiband filter and, therefore, the filter is capable of realizing the specifications of coupling coefficients at all passbands. To verify the presented concept, four experimental examples of filters with a dual-band Chebyshev, triple-band Chebyshev, dual-band quasi-elliptic, and triple-band quasi-elliptic response have been designed and fabricated with microstrip technology. The measured results are in good agreement with the full-wave simulation results.     

Realization of a dual-mode bandpass filter exhibiting either a Chebyshev or an elliptic characteristic by changing perturbation's size

A dual-mode resonator with square patches attached to inner corners of a conventional microstrip loop resonator is proposed. The two types of coupling between the degenerate modes are described by changing the perturbation's size for realization of either a Chebyshev or an elliptic function filter. A novel type of dual-mode microstrip bandpass filter using degenerate modes of this type of dual-mode resonators is developed. It is shown that the perturbation's size determines the filter characteristic, whether it is Chebyshev characteristic or elliptic characteristic.     

一种新型广义交叉耦合滤波器的设计

含广义交叉耦合的N个谐振器滤波器,即含源-负载交叉耦合的滤波器能产生N个传输零点,通过给出这种滤波器的等效网络模型和传输函数,设计了两种新颖六边形结构的含源-负载交叉耦合的微带滤波器,一种为对称结构,一种为非对称结构.对其进行了仿真分析,仿真结果与理论值吻合较好.与传统两腔发夹形滤波器相比,这种两腔六边形结构的滤波器尺寸要缩小27.5%,频率选择性更高.     

微屏蔽三线对称结构带通滤波器设计

对薄膜支撑空腔型微屏蔽传输线进行分析,提出微屏蔽传输线的物理结构。为了验证微屏蔽传输线在毫米波应用的优势,利用类比平行耦合微带线滤波器的方法设计了一种4阶切比雪夫三线对称结构微屏蔽线滤波器。通过对该微屏蔽腔体结构进行HFSS仿真,得到中心频率35 GHz的宽带滤波器,带宽15 GHz,带内插损小于0.5 dB,带外抑制>40 dB@53 GHz,器件尺寸8.24 mm×1.5 mm×0.65 mm。该设计为基于平面传输线的滤波器在毫米波频段的实现提供了一种可行的方法。     

Precise Design of Coaxial Low-Pass Filters

The coaxial low-pass filters described are of the conventional stepped impedance type consisting of a cascade of alternating low and high impedance sections of line. Exact prototype filters having Chebyshev equal-ripple characteristics are obtained from published tables giving the characteristic impedances of the sections. The capacitive discontinuities at the junctions are compensated by a new method which is exact at the cutoff frequency, and nearly exact in the region of this frequency. The production of low-pass filters with a passband VSWR of 1.05 or less is feasible and experimental results are described for such designs.     

Miniature high-Q double-spiral slot-line resonator filters

A new class of low insertion-loss miniaturized filters using slot-line resonators is proposed. Miniaturization is achieved by terminating the slot line with a double-spiral inductive termination at both ends. Using this miniaturized resonator, both positive and negative couplings may be realized, and therefore, both standard coupled-line and cross-coupled quasi-elliptic filters are realizable. The unloaded Q of these slot-line filters is considerably higher than that of miniaturized microstrip filters of comparable dimensions due to the inherent higher Q of the slot line. To demonstrate the validity of the design procedures and the performance characteristics, two different types of filters were fabricated and tested. One is a four-pole Chebyshev filter and the other is a quasi-elliptic filter where, in each case, the full-wave simulations show very good agreement with measurements.     

低电压全BJT高阶对数滤波器设计

提出了一种1.2 V低电源电压全BJT任意阶低通对数滤波器的设计方法.该方法是由传输函数直接设计低通对数域滤波器,得到最优的BJT跨导线性单元和滤波器系统状态空间后,利用最优状态空间描述滤波器系统,对微分方程中的每一项,使用最优BJT跨导线性单元设计其对应的电路,进行组合,从而得到低通对数滤波器,实现了不同阶数、不同纹波的切比雪夫低通滤波器,理论分析和Pspice实例仿真表明,该方法能最优地实现所需电路的设计,具有电路简洁和低电压的特点.     

一种新颖的微带带通滤波器的设计

介绍一种选择性介于切比雪夫滤波器与椭圆滤波器之间、物理上也易于实现的带通滤波器,给出了它的传输函数,依此在切比雪夫滤波器设计参数的基础上进行该滤波器的综合,然后用耦合谐振滤波器的理论与公式来分析该滤波器的频率响应。该滤波器采用新颖的开环谐振器耦合结构来实现,结果在保持很好的线性与较高的矩形系数的同时,体积也做得较小。     

一种新颖微带双通带带通滤波器的设计方法

本文提出了一种新颖的微带双通带带通滤波器的设计方法。该微带双通带滤波器由两个中心频率不同的滤波器组成,并采用耦合线实现外部耦合。设计中引入源与负载之间的耦合,得到了额外的有限频率传输零点,改善了滤波器的衰减特性。通过调节源与负载之间耦合的强弱,可以适当地调节传输零点的位置。经设计并加工了一款4阶微带开环结构双通带滤波器,实测响应与仿真响应吻合较好,验证了该方法的有效性。     

Filters with Single Transmission Zeros at Real or Imaginary Frequencies

A new unified theory is presented for the synthesis of exactly equiripple low-pass prototypes having: a) one simple pole of attenuation at a real frequency; or b) a single pair of real-axis transmission zeros (giving linear-phase performance). These types of filters may be regarded as representing the least possible degree of complication over the conventional Chebyshev filter, and are usually realized with one extra cross coupling in the structure. It is demonstrated that this gives much improved skirt selectivity in the case of a finite frequency pole, making it a viable intermediate case between the Chebyshev and elliptic function filters, while in the case of real-frequency zeros, very flat group delay over 50 percent of the passband is achieved with minimal cost in insertion loss and skirt rejection. Approximate and exact synthesis techniques are described, including results for the previously neglected odd-degree case. Experimental results demonstrate agreement with theory.     

A Harmonic Rejection Filter Designed by an Exact Method

An exact design procedure for band-stop filters is used to design a transmission-line filter with one point of perfect match at a fundamental frequency and one point of infinite attenuation at a harmonic frequency. This design method is based on the mapping of the response of a low-pass prototype into that of a transmission line filter. Here a three-element Chebyshev filter is chosen as the prototype and the otherwise general procedure is adapted for the special case of rejection of the second harmonic.     

Compact U-shaped dual planar EBG microstrip low-pass filter

In this paper, a novel high-performance compact dual planar electromagnetic bandgap (DP-EBG) microstrip low-pass filter with a U-shaped geometry is proposed. By employing the unique DP-EBG configuration and the U-shaped geometry of the microstrip line (MLIN), the proposed structure achieves a wide stopband with high attenuation and a high selectivity within a small circuit area. Its passband ripple level is low due to the U-shaped geometry and the electromagnetic bandgap (EBG) structure with square patches inserted at the bends of the MLIN. The Chebyshev tapering technique is used to taper components of the proposed structure in order to eliminate ripples caused by the EBG periodicity. The structure was fabricated and the measured results are in good agreement with the simulated results. This novel design demonstrates superior low-pass filtering functionality and can easily be applied to monolithic circuits.