Dual and tri-band bandpass filters based on novel Π-shaped resonator

A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.     

基于奇偶模分析法的四模谐振器结构的双通带带通滤波器设计

提出了一款基于四模谐振器的新型双通带带通滤波器.设计的四模谐振器基于微带线结构,由四个开路枝节和一个短路枝节组成.两次采用奇偶模分析法对该四模谐振器结构进行分析.该四模谐振器的每个模式能够实现独立调节,同时每两个模式形成一个通带.采用源与负载耦合的馈电方式,提高滤波器的带外抑制性.该滤波器具有四个传输零点和四个传输极点.测试结果表明,该双模双通带滤波器工作于2.08GHz和6.07GHz,3dB带宽分别为11.06%和7.74%.设计的滤波器具有紧凑的结构,只有0.28λ_g×0.11λ_g大小.     

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.     

Bandpass Filter with Wide Stopband Using Composite Right/Left Handed Transmission Line

Abstract This paper presents a wide-stopband bandpass filter (BPF) based on mixed coupling of the composite right/left handed transmission line (CRLH-TL). First the CRLH-TL resonator is introduced and analyzed. Then mixed coupling (Both electric coupling path and magnetic coupling path exist) of the novel resonator is explained. Based on the structural features of the CRLH-TL resonators, this coupling path can generate an additional transmission zero near passband without increasing the overall size of the filter. Then, good selectivity of the proposed BPF can be obtained. Meanwhile, in order to get a wide stopband, two open stubs are employed to suppress harmonic response of the CRLH-TL resonator. The filter is developed and analyzed based on microwave network theory and equivalent circuit method. The proposed BPF has been designed, fabricated, and measured. The measured results agree with the predicted ones closely.     

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).     

A Dual-Band Filter Realized by Alternately Connecting the Main Transmission-Line With Shunt Stubs and Shunt Serial Resonators

In this letter, we present a novel network for dual-band filter, the circuit of which is a mixture of shunt stub bandpass filter and shunt serial resonator bandstop filter. The stopband of the bandstop filter will split the passband of the bandpass filter and result in a dual-band response. The simulated and measured results are given. This kind of filter has the advantage of bigger and controllable bandwidths and lower insertion loss compared with traditional SIR dual-band filters.      

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 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.     

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.     

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.     

双频带通滤波器的优化设计

利用阶跃阻抗谐振器优化,设计了一个工作在无线局域网(2.4/5.2GHz)的双频带通滤波器。通过奇、偶模分析,在阶跃阻抗谐振器理论计算公式基础上,根据不同的阻抗比条件,阶跃阻抗谐振器谐振频率比与阶跃阻抗高、低阻抗电长度之比的关系曲线,可以方便地确定阶跃阻抗谐振器的谐振频率和电长度,通过sonnet电路仿真软件验证了设计的合理性,并给出了用于无线通信2.4、5.2 GHz双频带通滤波器的设计结果。该带通滤波器可以分别在2.4、5.2 GHz处得到较好的通带性。由于交叉耦合的存在,该双频带通滤波器在两个通带端各有一个传输零点,以此来提高滤波器的通带频率选择性。最后,测量结果与仿真结果基本吻合。     

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 Dual-Band Filter Using Defected Stepped Impedance Resonator

This letter presents a novel approach for designing a dual-band bandpass filter by using defected stepped impedance resonator (DSIR). The resonant frequency of the DSIR is found to be much lower than that of the conventional microstrip stepped impedance resonator (SIR), which reduces the circuit size effectively. Two types of second-order DSIR microstrip bandpass filter operating at 1.85 and 2.35 GHz, respectively, are well designed according to the classical theory of coupled resonator filter. Then they are combined to construct a compact dual-band filter with a common parallel microstrip feed line, the measurement results of the fabricated filter have a good agreement with the simulation.     

Novel Compact Quarter-Wavelength Resonator Filter Using Lumped Coupling Elements

A novel compact quarter-wavelength resonator filter using the lumped coupling elements is presented in this letter. The filter not only has controllable transmission zeros near its passband, but also features compact circuit size. Based on the equivalent circuit model, a bandpass filter with the center frequency of 1.85 GHz has been designed and fabricated. Measured results have validated the theoretical analysis well     

Novel Patch-Via-Spiral Resonators for the Development of Miniaturized Bandpass Filters With Transmission Zeros

A novel patch-via-spiral resonator based on the dual-metal-plane configuration is proposed and examined. With the microstrip patch on the top plane serving as a capacitor and linking to the quasi-lumped spiral inductor on the bottom plane through a connecting via, the proposed dual-plane resonator structure located on the opposite sides of the single substrate may form a miniaturized one in the printed-circuit board fabrication. By suitably combining the proposed patch-via-spiral resonators, useful coupled-resonator pairs may be constructed to simultaneously provide electric and magnetic couplings. Based on these coupled-resonator pairs, a second-order bandpass filter with multiple transmission zeros is realized without requiring either the cross-coupled path or the source-load coupling. For design purpose, the equivalent-circuit model is also derived and verified. In this study, a fourth-order patch-via-spiral bandpass filter with both good passband selectivity and miniaturized size of only 22.14 mm times5.08 mm (i.e., 0.188lambda_g0times0.043lambda_g0) is implemented, where lambda_g0 denotes the guided wavelength of the 50-Omega microstrip line at center frequency     

Design of Dual-Band Bandpass Filters Using Stub-Loaded Open-Loop Resonators

In this paper, open-loop resonators loaded by shunt open stubs are proposed to design compact dual-band bandpass filters with improved out-of-band rejection characteristics. The second passband of the dual-band filter is obtained by tuning higher resonant modes of the open-loop resonator by the stub length and position. A tapped-line input/output feed structure is used for external coupling. Required external coupling is obtained by adjusting the tapping position and dimension of the stub-loaded resonator. A lossless transmission line model is used to determine the resonance properties of the resonator and the external quality factor. Theoretical predictions are verified by the experimental results of three dual-band filters.     

屏蔽壳结构高Q值混合谐振器集成带通滤波器

提出了一种基于混合谐振器的新型二阶带通滤波器,该混合谐振器由微带线和一个短路的铜柱线组 成,这可以利用射频收发系统的结构件空间,并方便与平面微带电路集成,以提高滤波器的品质因数,它的无载Q 值 为455,高于传统的微带谐振器。而且,通过源负载耦合和混合电磁耦合的方法,在通带两边分别有一个可调的传输 零点,提高滤波器带外抑制特性。实验结果表明,测试结果与仿真数据吻合良好。     

Miniaturized dual-band bandpass filter with good frequency selectivity using SIR and DGS

A miniaturized dual-band bandpass filter (BPF) using stepped impedance resonator (SIR) and defected ground structure (DGS) is presented. In order to get two desired passbands, two different transmission paths and source–load cross coupling have been implemented. One path is the SIR, and the other is the DGS. Meanwhile, it is easy to obtain good frequency selectivity by introducing several transmission zeros. The coupling scheme and current distributions are applied to demonstrate the flexible design approach. A dual-band BPF is designed, simulated, and fabricated to demonstrate the performance of the proposed dual-band filter. The measured results show that the fabricated dual-band BPF has two passbands centered at 2.41 and 3.52 GHz with the fractional bandwidth of 5.8 and 7.7%, respectively. The measured insertion loss is about 2 dB and 2.2 dB at the lower and upper passbands. The measured results show good agreement with the simulated ones.     

A Novel Quasi-Elliptic HTS Filter With Group-Delay Equalization Using Compact Quasi-Lumped Element Resonators in VHF Band

To produce a filter small enough to fit a 2-in wafer in the very high frequency (VHF) band while avoiding parasitic cross coupling among nonadjacent resonators, a novel quasi-lumped element resonator with interdigital capacitor, double-spiral inductor, and pad capacitor have been introduced. This resonator has not only a highly miniature structure but also a very weak far-field radiation. A ten-pole quasi-elliptic filter with group-delay equalization, which has a 7.1-MHz 1-dB passband and a center frequency of 257.5 MHz, is designed and fabricated on a 37.3 x mm x 30.1 x mm x 0.5 x mm LaAlO₃ substrate. The measured results showed a 0.24-dB insertion loss, a 15-dB return loss, and a 70-dB out-of-band rejection. Moreover, the group delay variation is less than 50 ns over 70% of the 1-dB passband and the band where the phase error ripple is within plusmn5^deg is more than 80% of the 1-dB passband. The overall experimental performance showed excellent agreement with the theory and simulation, which is a good proof of the advantage of our weak far-field radiation resonator. The result showed that the novel resonator is very suitable to fabricate narrowband ultrahigh frequency, VHF, or even lower frequency high-temperature superconductor filters on a 2-in wafer.     

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.