基于方形开环的双模滤波器设计

在传统方形开环谐振器的基础上,设计了一种新型的双模微带滤波器,该滤波器包含两个方形开环谐振器,在每个传统谐振器内部添加微带支路结构,通过微扰来实现频响特性的改善,由仿真结果可以看出,该设计的带内特性良好,带内波纹小于0.3dB,通带边沿均插入了传输零点,且传输零点处的S21〈40dB,截止边沿陡峭,实现了6%的相对带宽,整个滤波器的尺寸大小约为30mm×20mm,改进后的结构与传统结构相比降低了0.5GHz的中心频率,相对减小了16%的面积,进一步实现了小型化。     

具有宽上阻带和双陷波的超宽带滤波器

基于偏置环形谐振器和加载电容器的缺陷地结构设计了一种具有宽上阻带和双陷波的超宽带滤波器。利用奇偶模分析法分析三阶接地短截线的传输极点与结构的对应关系，得到了一个具有五个传输极点的结构。通过采用三阶接地短截线结构和偏置环形谐振器的级联结构得到通带和宽上阻带，通带范围为2.95～12.24 GHz，相对带宽达到122%，上阻带大于10 dB，衰减范围至28.04 GHz。引入两个相同的H形缺陷地结构，并且在缝隙处焊接电容器，在2.69 GHz处共同产生传输零点来改善滤波器带外抑制特性。使用两个不同尺寸的半H形缺陷地结构分别在5.64 GHz和8.31 GHz处产生陷波，陷波衰减分别为16 dB和20 dB，提高滤波器的抗干扰能力。     

新型双频窄带带通滤波器的设计

提出了1种新型双频窄带带通滤波器,由1段1/4波长的均匀阻抗线以及1/2波长的U型阶跃阻抗谐振器组成,输入输出采用抽头式.所设计滤波器中心频率为2.4/5.6 GHz,为无线通信系统中的常用频率.该滤波器的带外有3个传输零点的引入,增强了通带隔离度以及阻带的抑制特性,带内回波损耗低于-0.3 dB.双频窄带带通滤波器的...     

基于Si-BCB工艺Ka波段双模带通滤波器

介绍了一种应用于毫米波晶圆级集成基于Si BCB工艺的Ka波段双模带通滤波器。微带线结构的全波长谐振器具有低辐射特性,全波长环形阶跃阻抗谐振器（step impedance resonator, SIR）有两种正交谐振模式,可以减小滤波器尺寸。通过对基于环形谐振器的双模滤波器进行奇偶模分析,确定谐振器的设计参数。采用宽边耦合结构设计输入输出端口,具有高耦合度。仿真结果表明中心频率35 GHz,通带内插损1.2 dB,回波损耗优于30 dB,BW3 dB为15%。最后,采用Si BCB工艺制作滤波器并完成测试。测试结果为中心频率33.3 GHz,通带内插损1.17 dB,回波损耗优于30 dB,BW3 dB为18%。测试结果与仿真结果基本吻合。     

基于微带三模谐振器的超宽带带通滤波器设计

提出一种基于微带三模谐振器的超宽带带通滤波器设计.该滤波器由一个中心加载阶跃阻抗开路枝节的三模谐振器,及两组用于抑制谐波的新型哑铃型缺陷地结构组成.使用交指型馈电方式及在馈电处的地板开槽实现超宽带需要的的强耦合,利用缺陷地结构抑制高次谐波实现良好的阻带特性.仿真结果表明,所设计的滤波器通带3 dB相对带宽达到80％(4.06～9.48 GHz),通带内插入损耗小于0.58 dB,回波损耗大24 dB,通带外10 dB阻带覆盖到30 GHz,通带两侧附近均有一个传输零点,获得了陡峭的通带边缘,较好地实现了美国联邦通信委员会(FCC)授权的超宽带通信系统的频谱使用要求.该滤波器结构简单,谐振器自身尺寸小于中心频率下0.5λg×0.5λg.最小带线和最小缝隙宽度均不小于0.1 mm,易于低成本加工,具有较高的实用价值.     

基于并联负载发夹型谐振器的四阶带通滤波器

针对现代无线通信系统中平坦带通滤波器的需求,提出了一种并联负载的发夹型谐振器,并利用提出的谐振器构建了四阶平坦带通滤波器。首先,通过在发夹型谐振器磁场最强的位置（中心位置）设置电阻,设计了一种新的并联型谐振器,从而可以通过改变电阻值来灵活地调整固有品质因数;其次,采用具有高、低固有品质因数的耦合拓扑来构建四阶平坦带通滤波器。最后,在印刷电路板上制备了一个具有传输零点和平坦带通的四阶带通滤波器。实验结果表明,该四阶带通滤波器的实测结果与仿真结果吻合较好,与其他多阶带通滤波器相比,该四阶带通滤波器具有可灵活控制的固有品质因数和小于0.2dB通带平坦度。     

混合耦合电调滤波器设计

设计了一款调谐范围为1200~1800MHz的电调滤波器。在传统梳状线电调滤波器的基础上,通过折叠变化引入了级间电磁场混合耦合使其在传输特性曲线低频端产生了两个传输零点,提高了带外抑制能力。引入的源负载耦合技术使传输零点向通带靠拢,进一步改善了滤波器的带外抑制能力。经测试,该滤波器的带外抑制度达到50dBc(1000MHz)、30dBc(2000MHz)。     

基于中心对称结构的带宽可重构滤波器设计

为适应需求日益复杂的无线通信环境，充分利用紧缺的频谱资源，设计实现了基于中心对称结构及变容二极管的电可调微带带通滤波器。通过电磁仿真软件HFSS进行仿真实验，在加载枝节的开口环谐振器结构上，引入叉指结构和马刺线型耦合馈线完成滤波器的原型设计。在原有的基础上加入可调节电容值的变容二极管，调节低频传输零点，实现通带带宽可重构，从而达到灵活控制滤波性能的目的。实际测试表明该滤波器的初始相对带宽为5.1%,初始绝对带宽为170 MHz,变容二极管调节绝对带宽在140～200 MHz范围内，即82.4%～117.6%,中心频率在2.70～2.76 GHz,传输零点调谐范围在2.57～2.63 GHz,通带内插入损耗在0.9～1.5 dB,回波损耗在10～35 dB,测试结果与仿真基本相符，在S波段的带宽精密控制方向具有一定应用前景。     

采用双开口方谐振环对的紧凑微带双频带通滤波器

提出了一种零度馈电、具有开口谐振环对的紧凑微带双频带通滤波器,适用于短距离无线通信2.4GHz频段和3.5GHz固定无线接入(FWA)的频段。此滤波器使用开口谐振环作为基本谐振器单元,通过电耦合实现了第一带通特性,通过调谐内外环的间距产生第二通带。为了提高带外衰减,通过设计零度馈电结构来引入四个传输零点,从而获得了高选择性特性,该滤波器设计简单、结构紧凑。最后,仿真设计和制作了滤波器样品,仿真与实测吻合较好,满足了设计要求。     

225～512 MHz双腔数字调谐滤波器设计与实现

针对超短波无线通信系统对载波频率可调性、高选择性的需要,设计了一种同轴双腔数字调谐滤波器.该腔体滤波器在端口激励采用线圈开环耦合以增大传输带宽,双腔之间装配金属铜片调整耦合系数大小,滤波器中的控制电路板使用PIN管选通不同电容对滤波器中心频率实现大范围调谐.实测性能:工作频率为225～512 MHz;插入损耗≤6dB,3dB带宽为1％～2％;电压驻波比≤1.5.测试结果显示该滤波器指标优良、仿真与实测一致性较好,设计方法对于数字调谐滤波器的设计具有参考意义.     

Explicit design formulas for current‐mode leap‐frog OTA‐C filters and 300 MHz CMOS seventh‐order linear phase filter

The leap‐frog (LF) configuration is an important structure in analogue filter design. Voltage‐mode LF OTA‐C filters have recently been studied in the literature; however, general explicit formulas do not exist for current‐mode LF OTA‐C filters and there is also need for current‐mode LF‐based OTA‐C structures for realization of arbitrary transmission zeros. Three current‐mode OTA‐C structures are presented, including the basic LF structure and LF filters with an input distributor or an output summer. They can realize all‐pole characteristics and functions with arbitrary transmission zeros. Explicit design formulas are derived directly from these structures for the synthesis of, respectively, all‐pole and arbitrary zero filter characteristics of up to the sixth order. The filter structures are regular and the design formulas are straightforward to use. As an illustrative example, a 300 MHz seventh‐order linear phase low‐pass filter with zeros is presented. The filter is implemented using a fully differential linear operational transconductance amplifier (OTA) based on a source degeneration topology. Simulations in a standard TSMC 0.18µm CMOS process with 2.5 V power supply have shown that the cutoff frequency of the filter ranges from 260 to 320 MHz, group delay ripple is about 4.5% over the whole tuning range, noise of the filter is 420nA/√Hz, dynamic range is 66 dB and power consumption is 200 mW. Copyright © 2008 John Wiley & Sons, Ltd.     

Compact third-order microstrip bandpass filter designed by the distributed- to lumped-element equivalence

In reality, it is not easy to design microstrip filters for the sake of distributed-element effect. It is an effective approach to approximate distributed-element structures through appropriate lumped-element circuits. In this paper, some basic microstrip structures are discussed, whose equivalent lumped-element circuits are derived. Then, a novel microstrip filter is obtained by connecting these microstrip structures, according to the similar topology of the third-order lumped-element bandpass filter. The equivalent lumped-element counterpart of the proposed microstrip filter clearly reveals its physical mechanism, ie, how the resonances are created and coupled and how the transmission zeros are created. Furthermore, a set of the design formulas are presented, which can be used to calculate initial structure parameters and then facilitate design process. The proposed microstrip bandpass filter can realize a third-order elliptic bandpass response with one transmission zero at each side of the passband. In addition, two short-circuited stubs are added to input/output ports to create the third transmission zero. The filter is featured by good frequency selectivity and out-of-band suppression. For demonstration, an actual example was designed, fabricated, and measured.     

Symmetric dual-mode filter based on substrate integrated waveguide (SIW)

A planar four-pole dual-mode filter with symmetric transmission response based on substrate integrated waveguide (SIW) is proposed. The filter centered at 10 GHz, consisting of two TE₁₀₂–TE₂₀₁ dual-mode SIW cavities, is implemented in a single layer substrate by PCB process. A linear microstrip taper is used to implement the transition between 50 Ω microstrip and SIW. The measured results are in agreement with simulated results.     

The jaumann structure in wave-digital filters

This paper deals with an extension of the wave-digital filter structures introduced by Fettweis. A new structure is introduced, viz, the digital translation of the Jaumann structure. The Jaumann structure is a well-known canonical realization of analogue, symmetric, grounded lossless two-port networks. With this structure, transfer functions with complex transmission zeros can be obtained in a wave-digital realization, which is not possible by means of a wave-digital ladder filter. Two examples are given, one of which has been implemented using TTL digital integrated circuits showing excellent properties.     

Design of selective lowpass sampled-data and digital filters exhibiting equiripple amplitude and phase error characteristics

A method is presented for the design of reciprocal reactant sampled-data and digital filters exhibiting equiripple passband and stopband amplitude characteristics and approximating a linear phase characteristic such that the phase error response is equiripple too. the passband amplitude characteristic approximates unity transmission and the stopband amplitude characteristic approximates zero. Odd- and even-degree cases are considered separately. the stopband amplitude response is controlled by an arbitrary number of finite transmission zeros together with two (one) zeros at infinity for even (odd) transfer functions. All the available degrees of freedom are used for controlling the filter performances. Thus the resulting solutions are selective and have good amplitude and phase characteristics. A comparison between our method and a recently published method shows that this approach has higher stopband loss and smaller phase error ripple with wider bandwidth.     

Monotonic,critical monotonic,and nearly monotonic low‐pass filters designed by using the parity relation for Jacobi polynomials

A new class of continuous‐time low‐pass filter using a set of Jacobi polynomials, with all transmission zeros at infinity, is described. The Jacobi polynomial has been adapted by using the parity relation for Jacobi polynomials in order to be used as a filter approximating function. The resulting class of polynomials is referred to as a pseudo Jacobi polynomials, because they are not orthogonal. The obtained magnitude response of these filters is more general than the magnitude response of the classical ultraspherical filter, because of one additional degree of freedom available in pseudo Jacobi polynomials. This additional parameter may be used to obtain a magnitude response having either smaller passband ripples or sharper cutoff slope. Monotonic, critical monotonic, or nearly monotonic passband filter approximating functions can be also generated. It is shown that proposed pseudo Jacobi polynomial filter approximation also includes the Chebyshev filter of the first kind, the Chebyshev filter of the second kind, the Legendre filter, and many transitional filter approximations, as its special cases. Several examples are presented, and detailed formulas including the practical suggestions for their efficient implementation are also provided. The proposed nearly monotonic filter is compared with the least‐square‐monotonic filters, designed as critical monotonic, in details. The advantages of the new filters are discussed. Copyright © 2017 John Wiley & Sons, Ltd.     

Sallen and key-type RC-active filters with complex transmission zeros

A second-order minimum-phase RC-active filter with complex transmission zeros is presented. It employs one operational amplifier and is based on a well-known Sallen and Key resonator. By including an additional difference amplifier a second-order all-pass circuit is derived. Both networks have free network parameters which can be used for minimizing the sensitivities of the Q-factors of the poles and zeros.