Sharp-Rejection Wideband Bandstop Filters

In this letter, a novel transmission line configuration has been proposed to design a sharp-rejection, bandstop filter (BSF) with wide rejection bandwidth. The rejection bandwidth and the level of rejection are controlled by the characteristic impedances of the transmission lines. Design equations are obtained by using a lossless transmission line model. The proposed design has been verified in microstrip line by fabricating a prototype BSF of -20 dB fractional bandwidth of 100% at a stopband center frequency f₀ = 1.5 GHz. The filter structure is simple and easy to fabricate.     

具有良好选择性及带外抑制的小型低通滤波器

本文提出了一种具有良好选择性以及宽带带外抑制的小型低通滤波器结构。滤波器的每一级由一段微带线和交指电容构成。基于对每一级结构的分析,我们可以确定通带的范围。为了进一步提高带外的抑制性,对单级滤波器进行了周期性的级联。通过产生多个带外衰减极点来实现带外的宽带抑制。此滤波器3dB 截止频率3.67GHz,带内插损-0.9dB,带内回波损耗低于-13dB。通带到阻带的选择度为160dB/GHz。带外抑制从3.8GHz 到13.1GHz 低于-20dB。     

Compact Wideband Bandpass Filters With Wide Upper Stopband

In this letter, a T-shaped microstrip feeding arrangement is proposed to design wideband bandpass filter (BPF) using shorted slot-line resonators. This feed line produces frequency selective external coupling which is utilized to suppress unwanted harmonics. Up to sixth order harmonics are suppressed. Other advantages are low passband group delay variation, ease of fabrication, low insertion loss (IL), and compact size. A fabricated BPF of fractional bandwidth 56.3% at midband frequency 2.3 GHz has a maximum IL of 1.2 dB in its passband and 30-dB upper stopband extends over 11.53 GHz     

Compact Dual-Band Bandstop Filters Using Stepped-Impedance Resonators

This work presents a compact dual-band bandstop filter (DBBSF) that features two controllable stopbands at desired frequencies. Stepped-impedance resonators are utilized to realize the dual-stopband characteristics, and reduce size. The synthesis method is developed. An experimental circuit is fabricated and evaluated to validate the design concept. Measurements correlate well with the simulation results, and the size is 12.6% less than that of a standard DBBSF.     

Compact Planar Dual‐Wideband Bandstop Filters with Cross Coupling and Open‐Ended Stepped Impedance Resonators

This letter presents the design of a compact bandstop filter (BSF) operating at two frequencies. The proposed BSF consists of open‐ended stepped impedance resonators (OSIR) and an end‐shorted parallel‐coupled microstrip line (E‐PCML). The OSIRs are used to achieve the impedance‐controlled stopband positions. The wide BSF bandwidths are achieved through enhanced coupling of the E‐PCML. Explicit design guidelines are derived using a lossless transmission line model. To validate theoretical predictions, a prototype dual‐band BSF operating at 900 MHz and 2,100 MHz with fractional bandwidths of 72% and 36% respectively, is implemented in microstrip.     

Sharp-Rejection Ultra-Wide Bandstop Filters

In this letter, a modified optimum bandstop filter (BSF) design is presented. Broad stopband and sharp rejection characteristics are achieved by realizing three transmission zeros near the passband edges. Stopband rejection depth and bandwidth can be controlled by the impedances of the configuration. A lossless transmission line model analysis is used to derive design equations. Further, a compact geometry is chosen by replacing the low impedance section with its equivalent dual-high impedance lines, which facilitates convenient folding. To validate the theoretical prediction, a single unit sharp-rejecting prototype BSF having a 20 dB rejection bandwidth of 126% at 1.5 GHz has been fabricated.      

集成宽带折叠半模基片集成波导带通滤波器

 本文提出并设计了一种新型的折叠半模基片集成波导（Folded Half-Mode Substrate Integrated Waveguide: FHMSIW）宽带带通滤波器,并给出了FHMSIW上层金属层槽缝式和中间金属层槽缝式宽带滤波器的仿真和测试结果。相对于半模基片集成波导（Half-Mode Substrate Integrated Waveguide: HMSIW）槽缝式滤波器,由双层PCB制作的FHMSIW槽缝式滤波器的尺寸减小了约一半。同时测试结果和仿真结果表明该宽带滤波器具有损耗小、带外抑制好等特性。     

Waveguide Bandstop Elliptic Function Filters

Using the "natural prototype" for elliptic function filters, a design procedure is presented for a class of waveguide bandstop filters, which exhibit equiripple passband and stopband responses. Due to the availability of explicit formulas for element values in the natural prototype elliptic function filter, the design procedure is entirely analytic and does not require numerical synthesis techniques. The resulting physical structure is the familiar uniform guide with iris-coupled series stubs. Unlike the bandstop filters designed from maximally flat or Chebyshev prototypes, the elliptic function design results in stubs that are not exactly three-quarter-wave coupled.     

Electronically Tunable Microwave Bandstop Filters

The design procedures for varactor tuned bandstop filters are presented. A novel circuit technique for realizing bandstop filters with a symmetrical frequency response is described and explicit design formulas are presented. The physical design and experimental performance of a three cavity varactor tuned bandstop filter tunable around 4 GHz is presented. Experimental results are substantiated with computer analysis which includes the effects of varactor resistance.     

New Narrow-Band Dual-Mode Bandstop Waveguide Filters

A complementary relation between a dual-mode bandpass and bandstop waveguide filter is found. Then a new idea for constructing a bandstop filter is developed. Two trial samples of bandstop filters are constructed to demonstrate the principle.     

Compact Wideband Bandpass Filters Using Stepped-Impedance Resonators and Interdigital Coupling Structures

This letter proposes a microstrip $lambda/4$ interdigital stepped-impedance resonator whose impedance ratio can be very low and coupling strength between adjacent resonators can be very large. On the basis of the proposed structure, one four-pole Chebyshev and one four-pole generalized Chebyshev filter with 0.05 dB equal-ripple bandwidths of 48% and 46%, respectively, are designed and fabricated. Both implemented filters have a compact size, a wide passband, a wide upper stopband, and a high spurious passband at near 5.1 times the center frequency. Good agreement between measurements and simulations is observed.      

A Microstrip Ultra-Wideband Bandpass Filter With Cascaded Broadband Bandpass and Bandstop Filters

This paper develops a novel ultra-wideband bandpass filter by cascading a broadband bandpass filter with another broadband bandstop filter. Properly selected impedances of transmission lines achieve broadband bandpass and bandstop filters and make independent designs possible. Detailed design and synthesis procedures are provided; moreover, agreement between measured and theoretically predicted results demonstrates feasibility of the proposed filter. Due to its simple structure, the ultra-wideband bandpass filter newly introduced in this paper is suitable for integration in the single-chipped circuit or implementation on printed circuit boards.     

Frequency-Selective Limiters Using Nonlinear Bandstop Filters

This paper presents a novel design for frequency-selective limiters based on reflection-mode nonlinear bandstop filters. This technique enables the use of low-Q lossy resonators for high-Q bandstop filter applications. Frequency-selective limiters described here achieve fast switching, high levels of power limiting, and flexible channel bandwidth. The prototype for a third-order device indicates 2-dB insertion loss for low RF powers. At high RF powers, it demonstrates 18-dB limiting level, 3-dBm limiting threshold, and 300-MHz limiting bandwidth. The switching speed is less than 10 ns, thus the spike leakage is minimized. The single-channel limiters are cascaded to provide limiting in wideband channels. The multichannel device is able to compress the dynamic range of the signals over 30 dB.     

基于反向耦合线的超宽阻带带阻滤波器

提出了一种全新的超宽阻带带阻滤波器结构。该结构由一段加载开路传输线的反向耦合传输线和一对开路传输线并联构成。理论分析表明,通过适当设置电路参数,该滤波器可以产生多个传输零点,构成一个具有高选择性高抑制性的宽带带阻滤波器。通过改变滤波器中的电路参数,特别是其中传输线的特征阻抗,可以灵活地调整滤波器的阻带带宽、阻带衰减和通带性能。基于这一理论,设计了一种宽带带阻滤波器。测试结果表明,该滤波器不仅可以提供109.40%的20dB相对阻带带宽和过渡尖锐的阻带,更可以提供高达105.73%的25dB相对阻带带宽。     

TEM Pseudoelliptic-Function Bandstop Filters Using Noncommensurate Lines

A synthesis procedure for distributed bandstop filters that approximate an elliptic-function response is described. Existing tables of lumped constant elliptic-function filters are used together with an approximate transform that exchanges commensurate Foster sections for noncommensurate pairs of stubs or coupled lines. The method is usable for all bandwidths up to about 100 percent, providing that networks with a relative bandwidth of more than 50 percent are considered to be pseudo-low-pass.     

达哈布风光(埃及,西奈半岛)

为了抑制杂波,需要在通信系统中安装带阻滤波器.采用切比雪夫低通原型设计带阻滤波器,用介质同轴谐振器加载电容的结构实现串联谐振,用π型LC网络实现1/4波长传输线.采用高品质因数(Q)、高介微波介质材料制作了中心频率为933 MHz、阻带衰减大于40 dB的带阻滤波器,测试结果符合设计要求.滤波器具有体积小,性能稳定等特点.     

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。     

A Novel Band-Reject Element for Pseudoelliptic Bandstop Filters

A novel band-reject element for the design of inline waveguide pseudoelliptic band-reject filters is introduced. The element consists of an offset partial-height post in a rectangular waveguide in which the dominant TE₁₀ mode is propagating. The location of the attenuation pole is primarily determined by the height of the post that generates it. The element allows the implementation of weak, as well as strong coupling coefficients that are encountered in asymmetric band-reject responses with broad stopbands. The coupling strength is controlled by the offset of the post with respect to the center of the main waveguide. The posts are separated by uniform sections of the main waveguide. An equivalent low-pass circuit based on the extracted pole technique is first used in a preliminary design. An improved equivalent low-pass circuit that includes a more accurate equivalent circuit of the band-reject element is then introduced. A synthesis method of the enhanced network is also presented. Filters based on the introduced element are designed, fabricated, and tested. Good agreement between measured and simulated results is achieved     

Synthesis of Even-Order Equally Terminated Transmission-Line Bandstop Filters

An exact synthesis procedure for the design of even-order equally terminated transmission-line bandstop filters is described. The method is optimum in the sense that it does not introduce redundant unit elements into the network. The final network is obtained in the form of a cascade of unit elements and shunt open-circuited stubs.     

Sharp Cutoff Microwave Filters

A class of sharp cutoff filters using combinations of lumped constant and distributed constant reactance have been analyzed and a test made of one type. The filters are developed in accordance with image parameter theory and are m-derived. Both high-pass and low-pass types are analyzed. The improvements over previous sharp-cutoff image parameter filters are predictable band limits and more predictable response. The derivations hold for all frequencies and are not approximations good only for short lengths of distributed constant reactance. Also, this class of filters have much sharper cutoffs than can be obtained with an equivalent number of sections designed using modern network theory. Some of these filters have fairly flat response close to the sharp-cutoff and are useful as end-matching sections. Curves and design equations are presented for three types---two high-pass and one low-pass filter. A seven-section high-pass filter was designed and tested. Its cutoff rate was 87db in a 3 per cent bandwidth located in the 300-Mc region. The pass-band width was greater than 30 per cent.