Design of Balanced Dual‐Band Bandpass Filter with Self‐Feedback Structure

A balanced dual‐band bandpass filter based on λ/2 stepped‐impedance resonators and open‐loop resonators is proposed in this letter. By employing a type of self‐feedback structure, an extra transmission zero is introduced near the common‐mode resonance frequency, and the common‐mode signal is suppressed. The measured results indicate that the filter can operate in 2.46 GHz and 5.6 GHz bands, and the insertion loss is 1.85 dB and 1.9 dB, respectively. Also, better common‐mode suppression is achieved.     

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.     

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 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).     

A microstrip folded compact wideband band-pass filter with wide upper stopband

A miniaturized wideband band-pass filter with a 3-dB fractional bandwidth of 109.3% (1.53 GHz to 5.22 GHz), high out-of-band attenuation greater than 25 dB, and wide upper stopband up to 14 GHz is proposed. The design consists of a dual-composite right/left handed resonator, embedded open-circuited stub, and a pair of quarter-wavelength short-circuited stubs. These elements are coupled in the near distance to form a miniature filter with a compact occupied area of 0.21 λ _g × 0.19 λ _g (≈ 0.013 cm²). The optimized filter has multi-transmission poles in the passband, substantially improving the return loss and insertion loss characteristics. The behavior of the passband and stopband is verified against the results of a lumped element model and matrix analysis with a full-wave moment-based analysis and actual measurements. The results of this verification and a comparison with the performance of filters in other references indicate that the proposed filter is very efficient and applicable to compact microwave systems.     

A New Type of Miniature Ultra-Wideband Band-Pass Filter with Coplanar Waveguide Fed

A novel miniature ultra-wideband (UWB) bandpass filter with coplanar waveguide (CPW) fed is proposed. The size of the filter is reduced largely because of combining the wideband couple gap and parallel-coupled CPW line (not cascading multiple resonator), and the length of realized filter is only 0.42 λ _g0 (λ _g0 is the guiding wavelength at central frequency). The measured insertion loss is less than 2.0 dB, and the group delay variation is less than 0.2 ns within the UWB passband. Basic agreement between the simulated and measured results has been achieved.     

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.     

Compact circular-patch-based bandpass filter for ultra-wideband wireless communication systems

Ultra-wideband (UWB) is a radio technology that enables low-power-level, short-range, and wide-bandwidth communication, and it has been widely applied in personal area networks, precision geolocation, medical, surveillance, and vehicular radar systems. Since Federal Communications Commission released the unlicensed use of the UWB range (3.1–10.6 GHz), a significant attention has been paid to the development of UWB devices, particularly UWB bandpass filters. In this paper, we propose a novel UWB bandpass filter based on circular patch resonator that is grounded by via and perturbed by slits and defected ground structures. The resonator’s behaviour is analysed in detail and it is shown that its specific configuration allows a flexible control of the three lowest resonant modes, which are used to form UWB passband. To demonstrate the potential of the resonator, a UWB filter has been designed, fabricated, and measured. The filter is characterized by the insertion loss lower than 1 dB and return loss higher than 17 dB within the passband, as well as by very small group delay variation of only 0.07 ns. Also, the filter exhibits suppression higher than 19 dB up to 30 GHz, and very small overall dimensions of only 0.31λ_g × 0.31λ_g, and thus it outperforms other published UWB filters.     

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.     

High Tc superconducting three-pole parallel-coupled bandpass filters made from laser ablated YBa2Cu3O7 − δ thin films

We have investigated three-pole parallel-coupled bandpass filters with fractional bandwidths of about 6% and 3% at a center frequency of 10.5 GHz utilizing high T_c superconducting YBa₂Cu₃O_{7 − δ} thin films. The films were deposited on LaAlO₃ substrates by pulsed laser ablation. Microwave responses of the filters were measured as a function of temperature and input power. The performance of the 3% bandwidth filter exhibits low insertion losses of about 0.48 dB and 0.79 dB at 20 K and 77 K, respectively. The insertion loss in the 6% bandwidth filter was 0.96 dB at 77 K. Both filters showed return losses better than 15 dB. High T_c superconducting bandpass filters showed good reproducibility. They were also compared with equivalent gold filters which showed insertion losses of more than 8 dB at 77 K.     

圆形开槽贴片微带双模带通滤波器

提出了一种新颖、简单的圆形贴片上刻蚀小方槽的微带双模带通滤波器结构.该滤波器仿真的通带中心频率为5.9 GHz,最大回波损耗优于-31.5 dB,通带内最小插入损耗为- 0.7 dB,3 dB带宽为23.73％.实测和仿真结果相一致.     

基于LTCC的Ka波段带通滤波器的设计

设计了一种基于低温共烧陶瓷技术带状线形式的Ka波段带通滤波器,该滤波器被埋入11层的基板中。提出一种类同轴结构来减小共面波导到带状线转换之间的阻抗不连续性。整个带状线滤波器采用了金属直通孔来实现接地和屏蔽功能。测试结果表明,滤波器中心频率为34.69GHz,带宽1.73GHz内最大插入损耗为-4.5dB,通带内回波损耗低于-13.45dB。该测试结果包含两个射频接头。整个滤波器尺寸为9.8mm×5mm×1.056mm。这种紧凑埋置式的结构和测试结果表明,该带状线滤波器适合于毫米波多芯片组件的应用。     

一种低插入损耗的180 GHz腔体滤波器

基于H形感性窗结构设计了一款低插入损耗的8阶波导腔太赫兹滤波器.经Ansoft HFSS对滤波器进行仿真优化后,滤波器采用传统的数控铣进行实物加工.测试结果表明:滤波器的中心频率位于179.1 GHz,1 dB相对带宽为8.7％.滤波器中心频率处的插入损耗为0.34 dB,回波损耗优于18.9 dB.所设计的太赫兹腔体...     

Multi‐harmonic Suppression Band‐Pass Filter for Communication System

For the purpose of decreasing intermodulation distortion, a new multi‐harmonic suppression band‐pass filter based on a microstrip radial stub is studied. Compared with traditional resonator filters, the new filter can suppress the second, third, and even fourth harmonics directly. The dimension of the filter is about 0.3 λ_g0 × 0.13 λ_g0 (λ_g0 is the guiding wavelength at the resonant frequency). Only one gap was introduced, so lower insertion loss can be obtained. Basic agreement between the measured and simulated results has been achieved.     

A Low Loss X-Band Quasi-Elliptic Ferroelectric Tunable Filter

A compact high quality factor four-pole X-band tunable quasi-elliptic bandpass filter is presented in this letter. The filter is enabled by high-Q ferroelectric barium strontium titanate capacitors and open-loop resonators. The central frequency of 8.35 GHz and the frequency tuning range of 500 MHz (6%) are achieved with a dc bias voltage of 30 V. The selective filter has a fractional 1 dB bandwidth ranging from 5.5% up to 7.3%. The measured insertion loss and return loss are 5.7-3.5 dB and 10.2-7.9 dB, respectively, with a dc bias range of 0 to 30 V. To the best of our knowledge, this is the best analog tunable performance and selectivity in X-band.     

Pi型电感耦合LTCC滤波器的寄生感性耦合研究

对二阶Pi型电感耦合LTCC滤波器中各个元件的电容及电感寄生效应进行了分析,提出了一种新的寄生电感耦合分析方法,并根据分析结果设计了一个二阶Pi型电感耦合和一个二阶Pi型电容耦合LTCC带通滤波器,其中,电感耦合滤波器的设计指标为:中心频率2.45GHz,相对带宽32.65%,带内插入损耗2dB,回波损耗18 dB;电...     

Novel Bandpass Filter Configuration Using Coupled Linear Tapered Line Resonators

A novel tapped bandpass filter composed of two‐coupled linear tapered‐line resonators (LTLRs) is proposed. Multistepped resonators are applied to analyzing LTLRs, which are difficult to analyze directly. Through this analysis method, fundamental characteristics of LTLRs and their filter design parameters can be easily derived. This new filter has insertion loss less than 0.6dB at 1.9 GHz, the return loss less than 18dB in the range 1.8‐1.93GHz and 12.3% 3dB bandwidth. Experimental results of fabricated filter are in good agreement with the design results.     

十字形贴片双模微带带通滤波器

基于传统的贴片型双模微带带通滤波器,提出了一种结构新颖、简单的滤波器.该结构是在十字形贴片谐振器上刻蚀正交的T形槽通过中心处的方开槽相连.对该结构进行优化,优化后的滤波器能在通带两侧都产生衰减极点,提高阻带的抑制能力,同时保证滤波器的小型化.该滤波器仿真结果表明通带中心频率为2.75 GHz,最大回波损耗优于-32dB,通带内最小插入损耗为0.60dB,3dB带宽达到59.8％,实测和仿真结果相一致.     

应用于WLAN／WiMAX的新型双模双通带微带滤波器

提出了一种新型应用于WLAN／WiMAX的对称T型开路支节加载的双模双通带滤波器,并对其进行了奇偶模分析,电场分布和电流分布分析。该滤波器的两个通带分别由奇模和偶模产生,且具有3个传输零点,带内插损分别为O．76dB／1．13dB,带内反射分别为-19．2dB／-15．1dB,在3．75—7．33GHz内,其衰减达到-20dB以下,具有高选择性和宽阻带的特性,且滤波器的卖测结果与仿真结果非常吻合。该双模滤波器具有非常小的尺寸,大小为14．03minx31．48mm,即0．15λg×0．34λg,所以该双模滤波器在工程领域非常具有应用价值。     

一种高抑制小型化带通滤波器

该文提出了一种具有3个传输零点的高带外抑制小型化带通滤波器。通过耦合控制可在梳状线滤波器响应中引入3个传输零点。通过源/负载耦合和传输线上刻蚀的马刺线可降低带外抑制,使滤波器获得更好的性能。设计并制作了一款小型化带通滤波器实物,仿真结果表明,该文设计的滤波器工作中心频率和相对带宽分别为2.12 GHz和20%,该滤波器的回波损耗优于40 dB,插入损耗小于0.2 dB,带外抑制小于40 dB。此外,该滤波器还具有结构简单紧凑、易加工等特点,实物测试结果与仿真结果基本一致。