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.     

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.      

Miniaturized Bandstop Filter Using Meander Spurline and Capacitively Loaded Stubs

A miniaturized bandstop filter (BSF) is introduced in this paper. The filter consists of one meander spurline and a pair of capacitively loaded stubs. The meander spurline with low resonant frequency and improved slow‐wave factor exhibits excellent resonant bandgap characteristics which can be modeled by a longitudinally coupled resonator. The design of the proposed microstrip BSF is presented, and its performance is measured. Measurements show that there is a stopband from 2.3 to 5.6 GHz with S₂₁ less than –20 dB. The total length of this BSF equals 23 mm.     

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.     

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.     

宽阻带平面低通滤波器的设计

低通滤波器是通信系统中关键的器件之一,常作为选频器件用来抑制干扰信号和谐波信号,因此低通滤波器阻带带宽成为关键指标.常见的平面低通滤波器采用短截线(分支线)或高低阻抗线结构,这些结构的低通滤波器阻带不够宽,一般在截止频率的2倍频或3倍频处出现寄生通带.本文使用等效的T形节替代低通滤波器中的串联传输线的方式实现了带阻滤波器嵌入到低通滤波器内部,既对低通滤波器的阻带上任意频段出现的寄生通带进行了抑制,又不影响低通滤波器的通带内性能,并给出等效T形节的综合设计公式.此结构综合设计方法严谨简单、易于平面电路实现,制作出来改进的低通滤波器对3倍频寄生通带进行抑制,扩宽了阻带带宽到4个倍频程以上,测试结果:通带带宽0~3GHz,通带插入损耗小于0.5dB,带外抑制3.6~12GHz大于60dB.     

Compact, Wideband Bandstop Filters With Sharp Rejection Characteristic

A compact unit of parallel coupled transmission line is presented for design of a compact, sharp-rejection, wideband bandstop filter (BSF). The rejection depth and bandwidth can be easily controlled by the coupled-line parameters. A lossless transmission line model is used for filter analysis. Design equations and graphs are presented in order to facilitate the design procedure. Theoretical prediction is verified in microstrip line by fabricating a prototype single section coupled-line BSF.     

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。     

SIR带状线带阻滤波器的设计

将具有阻带特性的微带马刺线结构引入到带状线中,设计了一款中心频率为2.32 GHz,相对带宽为9.5%,阻带衰减为50 dB的三阶马刺线式带阻滤波器。相比于传统的并联开路短截线型带阻滤波器,马刺线式带阻滤波器的横向尺寸大为减小,结构更加紧凑。采用SIR(stepped-impedance resonator)结构,按相同指标设计了一款三阶SIR马刺线式带阻滤波器。与马刺线式带阻滤波器相比,SIR马刺线式带阻滤波器结构更为紧凑,纵向尺寸缩小约17%,并具有更好的谐波抑制特性。     

基于SIW技术的毫米波滤波器研究与设计

基于基片集成波导（substrate integrated waveguide,SIW）结构设计了两款四阶的耦合带通滤波器,使用三维全波电磁场仿真软件HFSS对设计的两款滤波器进行了仿真设计和优化.由仿真结果分析得出,两款滤波器的工作频率均位于毫米波频段.第一款SIW滤波器实现了切比雪夫型响应,中心频率为20 GHz,带宽为2 GHz,通带内的插入损耗低于1.5 dB,回波损耗低于-20 dB,在阻带中对信号的衰减程度可以达到50 dB.第二款SIW滤波器实现了准椭圆函数型的响应,中心频率为29.1 GHz,带宽为300 MHz,通带内的插入损耗低于1 dB,回波损耗低于-20 dB,在通带到阻带的过渡中实现了两个陷波点.仿真结果表明,在毫米波滤波器设计中引入SIW结构,有利于优化滤波器尺寸,得到较好的滤波器性能指标,是毫米波滤波器发展的一个重要方向.     

A silicon micromachined four-pole linear phase filter

A 27-GHz four-pole linear phase filter constructed of micromachined cavities in silicon is presented. The structure of the filter consists of four side-by-side horizontally oriented cavities, which are coupled in turn by evanescent waveguide sections with three direct-couplings and one cross-coupling between the first and fourth cavity resonators. The cavities are reduced-height waveguide resonators and are fed by microstrip lines through slot apertures. A time-domain tuning technique is employed to improve the efficiency of the design synthesis. The measured results are presented and compared to those predicted by a finite-element-method model. The simulated filter response has a bandwidth of 2.2% centered at 27.480 GHz with an insertion loss of 1.4 dB at that frequency. The measured performance indicates a 1.9% bandwidth centered at 27.604 GHz with a deembedded insertion loss of 1.6 dB at that frequency and a measured unloaded Q of 1465.     

Wideband Bandpass Filter With Reconfigurable Bandwidth

this letter proposes a novel building block for developing tunable wideband bandpass filters. The proposed circuit block mainly consists of short circuit coupled lines and short circuit stubs with pin diodes as tuning elements. This work aims to demonstrate reconfigurable bandwidth of this type of filter. Two filters are designed and fabricated; one can be switched between a fractional bandwidth (FBW) of 16.3% and 35% at a center frequency of 1.9 GHz, and the other can be switched from a FBW of 27.8% to 37.4% at a center frequency of 1.9 GHz. The insertion loss and return loss in the first filter range from 4.17 dB to 0.4 dB and 27.54 dB to 19.04 dB. The second filter exhibits an insertion loss ranging from 0.73 dB to 0.43 dB and a return loss range from 31.1 dB to 27.7 dB. The tested filters show good agreement with EM simulations.      

High-performance microwave coplanar bandpass and bandstop filters on Si substrates

High-performance bandpass and bandstop microwave coplanar filters, which operate from 22 to 91 GHz, have been fabricated on Si substrates. This was achieved using an optimized proton implantation process that converts the standard low-resistivity (/spl sim/10 /spl Omega//spl middot/cm) Si to a semi-insulating state. The bandpass filters consist of coupled lines to form a series resonator, while the bandstop filter was designed in a double-folded short-end stub structure. For the bandpass filters at 40 and 91 GHz, low insertion loss was measured, close to electromagnetic simulation values. We also fabricated excellent bandstop filters with very low transmission loss of /spl sim/1 dB and deep band rejection at both 22 and 50 GHz. The good filter performance was confirmed by the higher substrate impedance to ground, which was extracted from the well-matched S-parameter equivalent-circuit data.     

Pulse shaper for ultra-wideband applications

The impulse-radio-based ultra-wideband system, which transmits and receives baseband pulses directly without a carrier, is very attractive for wireless sensor networks. It features very simple architecture and low power consumption [1]. In such a system, subnanosecond impulses are used not only for transmitting the data streams but also for downsampling the received pulses in the receiver. To realise high performance impulse generators, various circuit schemes have been proposed in the literature [2?4]. In addition, because of the coexistence of the UWB and WLAN radios at the frequency band of 5?6 GHz, in a recent ultra-wideband design an additional bandstop filter is urgently required to alleviate the potential interference. In [4], a higher-order derivative Gaussian pulse generator with band-notched characteristics at the WLAN band is proposed by utilising two microstrip bandpass filters. In this Letter, we propose a new ultra-wideband pulse shaper which demonstrates comparable performance but more compact size. The pulse shaper is composed of two parts: a thirdorder bandstop filter (BSF) and a third-derivative Gaussian pulse generator. The bandstop filter is realised by incorporating a new meandered V-sickle slotted ground structure. The experimental results reveal that the new design not only complies with the FCC emission mask but demonstrates excellent signal suppression at the 5 GHz WLAN band. It also occupies a smaller circuit area compared to that in the previous work [4].     

Waveguide Bandpass Filters for Millimeter-Wave Radiometers

A fundamental requirement for most mm-wave heterodyne receivers is the rejection of the input image signal which is located close to the local oscillator frequency. For this purpose we use a bandpass filter, which for heterodyne receivers is also called an image rejection filter. In this paper we present a systematic approach to the design of a waveguide bandpass filter with a passband from 100 to 110 GHz and upper rejection bandwidth in the range from 113 to 145 GHz. We consider two non-tunable filter configurations: the first one is relatively selective with 11 sections (poles) whereas the second one is simpler with 5 sections. We used established design equations to propose an initial guess for the geometries of the filters, optimized the geometries, constructed the filters using two different milling methods, measured their transmission and reflection characteristics, and compared the measurements with numerical simulations. Measurements of both filters agree well with simulations in frequency response and rejection bandwidth. The insertion loss of the 11-pole filter is better than 10 dB and that of the 5-pole filter is better than 5 dB. The 11-pole filter has a sharper attenuation roll-off compared with the 5-pole filter. The upper out-of-band rejection is better than 40 dB up to 145 GHz for the 11-pole filter and up to 155 GHz for the 5-pole filter.     

Design of the Compact Wideband Bandpass Filter With Low Loss, High Selectivity and Wide Stopband

In this letter, a novel compact wideband bandpass filter using the asymmetric stepped-impedance resonator (SIR) with one step discontinuity is designed and implemented to achieve characteristics of low loss, wide stopband and very high passband selectivity, simultaneously. The first two resonant modes of the asymmetric SIR are coupled together and applied to create a wide passband. The design procedure is discussed in detail. The proposed filter at center frequency ${rm f}_{0}$ of 4 GHz has very good measured characteristics including a low insertion loss of 0.5 $pm$ 0.3 dB, the bandwidth of 2.9–5.3 GHz, sharp rejection due to two transmission zeros in the passband edge. Experimental results of the fabricated filter show a good agreement with the predict results.      

A vertically integrated micromachined filter

A 10-GHz filter constructed of slot-coupled micromachined cavities in silicon is presented. The novel character of the filter lies in its structure, which consists of a microstrip feed to cavities via slot apertures and three vertically stacked slot-coupled cavities. The cavities are essentially reduced-height waveguide resonators. The measured results are presented and compared to a finite-element-method model. The simulated model has a bandwidth of 4% with an insertion loss of 0.9 dB at 10.02 GHz. The measured filter yields a 3.7% bandwidth with a deembedded insertion loss of 2.0 dB at 10.01 GHz. Various loss mechanisms are examined to explain the difference between simulated and measured insertion loss     

基于波纹耦合微带线的可调谐带通滤波器

设计了一种紧凑5阶双零点可调谐带通滤波器。通过在传统梳状线滤波器中引入波纹耦合微带线结构,该滤波器可以在中心频率调谐过程中保持绝对带宽恒定,同时尺寸相较于传统方法可减小50%。谐振器中引入分布式补偿电容利于滤波器应用于高介电常数衬底的微带线结构。基于源与负载间的耦合,引入两个传输零点来提高滤波器的衰减特性。HFSS仿真结果显示,当加载的电容值为2.43 pF时,滤波器的中心频率为1.48 GHz,带宽为194 MHz,插入损耗为1.36 dB。随着加载电容值从2.15 pF增加到2.93 pF,滤波器的中心频率从1.55 GHz减小至1.37 GHz。保持绝对带宽恒定的情况下,通带内的插入损耗小于1.5 dB。     

一种提高40 Gb/s非归零码系统中偏振度椭球对偏振模色散灵敏度的新方法

提出了利用光带阻滤波器提高 4 0Gb/s非归零码系统中偏振度椭球对偏振模色散灵敏度的方法 ,数值研究了不同滤波器带宽对偏振度椭球三个轴长度的影响。结果表明 ,加滤波器后偏振度椭球对差分群时延和主态旋转率的敏感度明显提高 ,考虑到滤波器引入的损耗 ,提出了在最大差分群时延为 2 0ps时滤波器的带宽应限制在 10GHz以下。另外 ,数值结果还表明在滤波器带宽为 10GHz时 ,小于 4 0ps2 的偏振相关色散不会对偏振度椭球三个轴的长度产生明显的影响     

A V-band planar narrow bandpass filter using a new type integrated waveguide transition

A surface mountable planar narrow bandpass filter is proposed and demonstrated at V-band. The filter is constructed using an integrated waveguide in an alumina substrate employing a novel microstrip line to waveguide transition. The insertion loss per one transition is less than 0.1 dB over 43 to 73 GHz. A fabricated three-pole Chebyshev filter exhibits an insertion loss of 3 dB with a 3.3% bandwidth at a center frequency of 62 GHz and the return loss is better than 15 dB in the passband.