Compact wideband bandpass filter using quad mode resonator

This paper presents a compact wideband bandpass filter for TETRA band applications. The proposed filter design is based on a quad mode resonator designed using small rectangular loop loaded with four Stepped Impedance Stubs (SISs) and a short circuit stub. The four modes of the resonator help in generating a wide passband. The use of SISs makes the filter compact. In addition to four transmission poles, the resonator inherently generates a transmission zero above the higher end of passband. Two transmission zeros are generated by the input/output coupling which helps in increasing the selectivity and also for achieving wide stopband. This filter provides a 3 dB fractional bandwidth of 30.33% and maximum insertion loss of 1.3 dB at the center frequency 0.36 GHz with a compact size of 0.125 λ_g × 0.085 λg (4.1 × 2.78 cm²).     

Dual-band bandpass filter based on mixed electric and magnetic coupling of the hybrid quasi-lumped resonator

A novel compact dual-band bandpass filter based on mixed coupling of the hybrid quasi-lumped resonator is proposed. The filter is composed of two independent signal paths, each can generate one passband with two identical hybrid quasi-lumped resonators. The proposal combines the mixed electric and magnetic coupling technology with this novel resonator in the filter design. Analysis of the filter has been done with the equivalent circuit method. To validate the approach, a dual-band bandpass filter operating at 2.4/5.2 GHz has been fabricated. Both passbands were realised with mixed coupling. An additional transmission zero is generated at either passband. Final fabricated filter has good band skirt, low insertion loss and good out-of-band performance. Reasonable agreement is found between the calculated, simulated and measured results. The implementation area is 0.21λ_g × 0.12λ_g.     

Compact microstrip lowpass filter with wide stopband and sharp roll-off using tapered resonator

In this article, a novel microstrip lowpass filter (LPF) with specifications such as sharp cut-off, wide stopband, low insertion loss and high return loss using tapered resonator is presented. The LPF has cut-off frequency of 1.11 GHz, where unwanted harmonics are suppressed by novel tapered cells. The bandwidth is enhanced, and the size is reduced as compared to the conventional tapered filter. The transition band is approximately 0.29 GHz from 1.11 to 1.4 GHz with corresponding attenuation levels of –3 and –20 dB, respectively. The stopband with greater than –20 dB rejection is from 1.4 to 8.9 GHz, insertion loss in the passband is less than 0.1 dB, return loss is less than –18 dB and the overall size of the filter is 0.12 × 0.073 λ_g. The proposed filter is fabricated and measured. The simulation and measurement results are in good agreement. This LPF is designed for microwave communication applications, especially wireless video transmitters.     

Design and analysis of a super compact wide-band bandpass filter based on metamaterial resonators

In this paper, a novel compact wide-band bandpass filter (BPF) with a wide frequency range is presented. This filter consisting of a multi-mode resonator (MMR) and four metamaterial unit-cells benefits from a very compact size. Unit-cells based on a complementary spiral resonator (CSR) including a metallic via, improve both upper and lower stopband rejection and compensate the insertion loss (I.L) within the passband altogether. This wide-band filter presents a 3-dB bandwidth of 7.7 GHz, ranging from 3 GHz to 10.7 GHz and the Insertion loss is less than 0.7 dB over the passband. The measured results are in good agreement with both the full-wave electromagnetic simulation and the proposed circuit model results. The dimension of the fabricated filter is 0.128 λ × 0.1 λ (i.e., 5.6 × 4.4 mm²). This filter is considerably compact compared to the other wide-band bandpass filters with the same substrate.     

Novel Quasi‐Elliptic Function Bandpass Filter Using Hexagonal Resonators with Capacitive Loading

A novel and compact elliptic‐function bandpass filter is proposed in this letter. The techniques of slot etching and the addition of open stubs are applied to enhance the self‐inductance and self‐capacitance of hexagonal open‐loop resonators. Thus, size reduction and improved transmission performance are obtained. Compared to the performance of the conventional design, the central frequency and insertion loss are reduced by 28% and 3.1 dB, respectively. Measurements show that the proposed filter has a fraction bandwidth of 23% at the central frequency of 1.84 GHz, and its insertion loss in the passband is less than ?1.5 dB. The bandpass filter occupies only 12 mm×21.2 mm (approximately 0.24λ_g×0.14λ_g).     

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.     

A novel microstrip lowpass filter with sharp roll-off and ultra-wide stopband using SICMRC

This paper presents a novel microstrip lowpass filter with sharp roll-off and ultra-wide stopband using stepped-impedance resonator and bended transmission line structure. The filter includes stepped-impedance prototype filter and stepped-impedance compact microstrip resonator cells that are combined in one structure. The proposed filter has good specifications such as sharp roll-off, ultra-wide stopband and low insertion loss. The transition band is approximately 0.25 GHz from 1.75 to 2 GHz with corresponding attenuation levels of ?3 and ?40 dB. The attenuation level in the stopband is better than ?20 dB that is achieved from 1.94 to 23 GHz, and the insertion loss in the passband is less than 0.4 dB. The proposed filter is fabricated and measured, and the simulation and measurement results are found to be in good agreement with each other.     

Compact and high-performance bandpass filter and diplexer based on SCMRC-loaded SIR

Bandpass filter (BPF) and diplexer, which are required to be compact size and high performance, are widely used in modern wireless communication systems. In this article, novel BPF and diplexer are designed using the proposed resonator called spiral compact microstrip resonator cell (SCMRC)-loaded stepped-impedance resonator (SIR). The SCMRC-loaded SIR is proposed using the slow-wave structure SCMRC to replace the low-impedance section of the conventional SIR. Compared with the conventional SIR, the new SCMRC-loaded SIR has a compacter size and can generate a transmission zero above its fundamental resonant frequency. As examples, a BPF with the central frequency at f ₀?=?1?GHz and a diplexer operating at 0.9/1.57?GHz are designed and fabricated. The fabricated BPF occupies a compact size of 0.07 λ ₀?×?0.035 λ ₀ and has a??60?dB rejection level wide stopband from 1.2 f ₀ to 3.8 f ₀. The fabricated diplexer occupies a compact size of 0.076 λ ₀?×?0.128 λ ₀ and has an up to??50?dB output isolation. Good agreement can be observed between the simulations and the measurements.     

A microstrip wideband bandpass filter based on λ/2 stub with spurious passband suppression scheme

In the design of bandpass filters, the use of λ/2 stubs of shunt configuration had been mostly unacceptable due to their effect of narrow stopband bandwidths in the ensuing filters. The design of bandpass filter presented in this article introduces 360° series transmission line segments to increase the stopband bandwidths to an acceptable level without affecting the wide passband. This designed filter has low insertion loss of less than –1.98 dB and a fractional bandwidth of 50% at 6 GHz mid-band frequency. A sharp rejection in the stopband is observed. To further widen the bandwidth of stopbands, a series capacitor and a shunt stub are used. The transmission line model of the filter is in good agreement with measured results. The filter is planar and is fabricated on FR-4 substrate which makes it cost-effective 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。     

基于开路T型结构的小型化超宽阻带滤波器设计

传统滤波器由于寄生通带的存在,其高频阻带性能较差。随着超宽带雷达系统和超宽带通信系统的发展,小型化宽阻带的滤波器已成为一项紧迫的技术课题。该文论述了一种普适性的基于开路T型结构的小型化超宽阻带滤波器结构,这种滤波器和传统滤波器相比,结构极为紧凑,5倍基频范围内的寄生通带均被抑制,而通带性能保持良好。基于此结构实际制作了一个截止频率为2.9 GHz的低通滤波器,测量得到的通带内平均插入损耗仅0.67 dB,带内平均驻波比为1.33,过渡带陡峭,40 dB矩形系数仅1.096,而所测得的阻带从3.23 GHz到10.30 GHz之内谐波抑制大于36 dB,从10.30 GHz到15 GHz之内谐波抑制大于27 dB;该滤波器的长度仅为传统的同类型滤波器的长度的37.1%,面积大大减小。仿真和测量结果表明该类型滤波器同时满足了小型化和宽阻带的性能需求。     

Dual band notched UWB-BPF based on hybrid microstrip-to-CPW transition

The research paper proposes a compact dual notched band ultra-wideband (UWB) bandpass filter (BPF). The basic architecture of the filter is developed using the hybrid microstrip-to-coplanar waveguide (CPW) technology, wherein a short circuited CPW in ground is coupled vertically via the dielectric to the microstrip lines on the top plane. The broadside alignment generates a three pole BPF with dual transmission zeros (TZs) on either passband/stopband edges which leads to minimum insertion loss passband and sharp roll-offs. Later, multiple spirals and split ring resonators (SRRs) are embedded in the CPW of the UWB filter to introduce the dual notches and widen the stopband respectively. The proposed filter is fabricated to justify its measured response. The proposed filter measures only 14.6 × 7.3 mm².     

Compact microstrip lowpass filter with very sharp roll-off using meandered line resonators

In this paper, a new compact size microstrip lowpass filter (LPF) with a very sharp roll-off is presented to apply in the modern wireless networks. The proposed LPF is designed using the series main resonators with meandered lines based on inductor-capacitor (LC) equivalent circuit analysis. The main goal is to achieve maximum-sharp roll-off by maintaining a wide stopband bandwidth and high return loss (RL). The main resonator of the proposed filter is consisted of two meandered line hairpin resonators (MLHR), and a meandered line T-shaped resonator (MLTR). The designed suppressor is composed of two coupled radial stubs to create a wide stopband. Low return loss in the passband, which has been created by the main resonator, is resolved by the suppressor structure with high return loss. The measured results show a ??3 dB cut-off frequency of 1.93 GHz. The very sharp transition band starts at 1.93 to 1.97 GHz (from ??3 to ??20 dB). The stopband is from 1.97 to 19.9 GHz (with the suppression level of ??20 dB). Also, the total size of the proposed LPF is only 13.3?×?10.1 mm².

     

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。     

基于多节SIRs的新型四通带滤波器设计

提出了一种基于多节1/2波长SIRs的具有通带可控的紧凑型四通带滤波器。该滤波器由上下两个谐振器A和B组成,谐振器A由两节1/2波长SIRs中心加载一段短路枝节组成,控制第二和第三通带;谐振器B由三节1/2波长SIRs中心加载一段短路枝节组成,控制第一和第四通带,最终得到了尺寸为8.09 mm×14.12 mm(0.10λ_g×0.17λ_g)的四频带通滤波器。实验结果表明,该滤波器的通带可控并且满足低损耗的要求,4个通带的中心频率分别为2.22/3.66/5.63/7.52 GHz,插入损耗分别为0.32/0.41/1.38/0.43 dB,每个通带的回波损耗都优于20 dB,实验结果与理论分析一致。     

Compact tri‐wideband bandpass filter with multiple transmission zeros

This paper presents a tri‐wideband bandpass filter (TWB‐BPF) with compact size, high band‐to‐band isolation, and multiple transmission zeros (TZs). The proposed TWB‐BPF is based on a multiple‐mode resonator (MMR), which is interpreted by the method of the even‐ and odd‐mode analysis technique. The MMR can excite 11 resonant modes, where the first two modes comprise the first passband, the next four modes form the second passband, and the last five modes are used to generate the third passband. In addition, 10 TZs are yielded to obtain high band‐to‐band isolation and wide stopband suppression characteristics up to 14.95f_c1 (f_c1 is the center frequency of the first passband). To verify the proposed filter, a TWB‐BPF with 3‐dB fractional bandwidths (FBWs) of 37.4%, 43.5%, and 40.4% is designed, fabricated, and measured.     

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。     

Transversal wideband bandpass filter with a wide stopband and multiple transmission zeros

Herein, we present a compact transversal bandpass filter (BPF) with an extremely wide upper stopband and multiple transmission zeros (TZ). Three signal transmission paths with shorted stubs and open-coupled lines allow signal transmission from input port to output port. Two resonant modes can be excited simultaneously and managed easily for bandpass response. Eleven TZs are achieved via transmission path cancelation; an extremely wide upper stopband with an attenuation level better than –12 dB is achieved up to 11.7 f₀, where f₀ is the center frequency (CF). In addition, bandwidth and CF can be controlled by adjusting electrical lengths. For proof of concept, a wideband BPF centered at 1.04 GHz with 3 dB fractional bandwidths of 49.2% was designed, fabricated, and evaluated. The overall circuit measures 0.045λ_g × 0.117λ_g; good agreement was observed between the measured and simulated results.     

基于阶梯阻抗的发夹结构低通滤波器设计

提出一种基于阶梯阻抗发夹谐振器的小型化微波低通滤波嚣,该滤波嚣仅由包含四节微带的阶梯阻抗发夹谐振器构成.设计结果表明,滤波器3dB通带从直流到2.8G,带内反射小于-20dB,带外抑制达到40dB.这种滤波器尺寸小,易制造,且具有陡峭的截止频率响应特性,可用于许多微波系统中.     

Miniaturized microstrip bandpass filter designed using rectangular dual spiral resonator

A miniaturized microstrip bandpass filter based on a rectangular dual spiral resonator (DSR) is proposed in this paper. The rectangular DSR bandpass filter is centered at 3.65 GHz to suit for Wireless LAN (IEEE802.11y) application. The proposed filter offers transmission zero at the high side of out-of-band response. Across the bandwidth, the measured minimum insertion loss is about 1.7 dB, while the measured return loss is better than 19 dB. Measurement results are good agreement and closed to the simulated ones. The total circuit size of the miniaturized bandpass filter is about 0.145λ_g by 0.135λ_g, where λ_g is the guided wavelength at 3.65 GHz.