New compact wideband bandpass filter using three parallel-coupledlines

A new miniature bandpass filter, comprising three-conductor short-circuited spurline resonators of approximately a quarter-wavelength long, with a very wide bandwidth approaching multioctaves is reported for the first time. The chain matrix of the filter resonator is derived. The new filter has been developed using microstrip line with less than 1 dB insertion loss over a passband from 2 to 8 GHz. Reasonably good agreement between the measured and calculated results is observed     

Compact bandpass filter realised using coupled linear tapered line resonators

A new compact bandpass filter composed of two coupled linear tapered line resonators is proposed. The two resonators are arranged in different planes. The filter is very small and has a very sharp response below its passband. It is also shown that this filter has a low insertion loss of 0.6 dB in the centre frequency and 10.5% 3 dB bandwidth.     

Tunable combline filter with continuous control of center frequency and bandwidth

A new combline filter structure with a continuous tunability for both the center frequency and bandwidth is presented in this paper. The passband-width tunability is achieved by placing variable coupling reducers between the filter resonators. The coupling reducers, operating as bandwidth control subnetworks, are designed as detuned resonators made up of a line segment ending in a variable capacitor. The proposed filter structure is experimentally validated with the design, construction in suspended stripline technology, and characterization of a low-cost filter prototype for terrestrial digital video broadcasting receivers operating in the UHF band (470-862 MHz). Other relevant factors, such as the intermodulation distortion produced by the varactors used to control the bandwidth electronically or the power-handling performance of the constructed filter, are also discussed. The reconfigurable filter module described in this paper is very suitable for the design of flexible multifunction receiver subsystems simultaneously supporting signals with a different bandwidth.     

Balanced Coupled-Resonator Bandpass Filters Using Multisection Resonators for Common-Mode Suppression and Stopband Extension

Novel fourth-order balanced coupled-resonator bandpass filters are proposed using suitably designed half-wavelength (lambda/2) multisection resonators for common-mode suppression. By properly designing the input/output (I/O) resonators associated with the filter composed of four bi-section resonators, a balanced filter with good common-mode suppression is realized, but its rejection bandwidth is rather limited. To widen the rejection bandwidth, the I/O bi-section resonators are replaced by the tri-section ones so that a balanced filter with good common-mode suppression and wide rejection bandwidth may be realized by suitably arranging the composed bi-/tri-section resonators. Specifically, a stopband-extended balanced filter with good common-mode suppression (>50 dB) within the differential-mode passband is implemented and its stopbands are also extended up to 5f₀ ^d with a rejection level of 30 dB, where f₀ ^d is the center frequency in differential-mode operation.     

Improved and compact 0.7 GHz tune-all bandpass filter

A compact tune-all bandpass filter is presented. This electronically tuned filter is based on series-coupled slow-wave resonators. It allows wide simultaneous and continuous tunings of centre frequency (+/-15% around 0.7 GHz) and bandwidth (from 50 to 100 MHz) with insertion loss IL<5.4 dB and return loss RL>11 dB. This two-pole bandpass filter exhibits also a very small surface of only 7.3times10^-3 lambda₀ ² and a -20 dB stop-band that extends up to 10 GHz     

Performance improvement and size reduction of microstrip dual-mode bandpass filter

A novel miniaturised dual-mode bandpass filter with multi-arc resonators is proposed. The size of the dual-mode filter can be reduced significantly by using the microstrip dual-mode resonator consisting of multi-arcs; meanwhile insertion loss and spurious response suppression are improved A prototype filter is designed and implemented at 3.6 GHz with 2.8% fractional bandwidth, which shows a low passband insertion loss of 1.02 dB and a wide stopband with rejection better than 20 dB up to about 8.5 GHz.     

Compact Bandpass Filters Based on Dual-Plane Microstrip/Coplanar-Waveguide Structure With Quarter-Wavelength Resonators

Compact wideband bandpass filters are proposed based on the dual-metal-plane structure consisting of both microstrip and coplanar-waveguide (CPW) quarter-wavelength resonators. By combining the advantages of dual-plane microstrip/CPW structure and stepped-impedance resonators, strong couplings between resonators may be accomplished so that the fourth-order cross-coupled filter with compact size and wide bandwidth may be realized. To further improve the selectivity, the sixth-order cross-coupled filter composed of four microstrip and two CPW resonators is implemented. Specifically, the implemented filters have the merits of compact size, good insertion/return losses, wide fractional bandwidth, and better selectivity. Good agreement between simulated and measured responses of these filters is demonstrated     

Piezoelectric-transducer-controlled tunable microwave circuits

This paper introduces a new method to tune microwave circuits of phase shifters, filters, resonators, and oscillators, controlled by a piezoelectric transducer (PET) with computational and experimental results. An optimized PET-controlled phase shifter is demonstrated to operate up to 40 GHz with a maximum total loss of 4 dB and phase shift of 480°. PET-controlled tunable bandpass filter, ring resonator, and one-dimensional photonic-bandgap resonator show a very wide tuning bandwidth of 17.5%-28.5% near 10 GHz with little performance degradation. A new PET-controlled or voltage-controlled dielectric-resonator oscillator (DRO) is demonstrated with a tuning bandwidth of 3.7% at the center frequency of 11.78 GHz. The tuning bandwidth is slightly less than that of a mechanical tuning using a micrometer-head-controlled tunable DRO with a tuning bandwidth of 4.7%. The new tuning method should have many applications in monolithic and hybrid microwave integrated circuits     

Design of a Wide Stopband Microstrip Bandpass Filter With Interdigital Resonators

In this letter, a novel microstrip bandpass filter (BPF) with interdigital resonators is presented. With the interdigital resonators and shorted asymmetrical coupled-lines, a wide bandwidth with sufficient rejection level can be achieved easily. A full-wave electromagnetic simulator IE3D is used, and the prototype of the BPF is fabricated and measured. Comparisons of simulated results and experimental data are shown; moreover, good match validates the proposed filter.      

Design flexibility of an open-loop resonator filter using similarity transformation of coupling matrix

In this letter, the design flexibility of an elliptic-response open-loop resonator filter is achieved through similarity transformation of the coupling matrix. To verify the proposed method, a compact four-pole elliptic-response bandpass filter is designed using the conventional structure with open-loop resonators. Designed filter has the resonators with very narrow spacing for the required coupling coefficient and it is impossible to implement a filter with wider fractional bandwidth. Two possible configurations to overcome this problem are presented through similarity transformation of the coupling matrix. From this design flexibility, a filter with wider fractional bandwidth is designed with realizable design parameters.     

A New Class of Low-Loss High-Linearity Electronically Reconfigurable Microwave Filter

A novel electronically reconfigurable microwave bandpass filter based on a switched delay-line approach is presented. In contrast to conventional tunable filters, the approach enables the lossy and nonlinear switching elements to be used as part of the coupling elements rather than within the resonators. Therefore, the filter distinguishes itself through its ability to provide a wide tuning bandwidth with low passband loss and high linearity. Theoretical analysis of the approach is presented in this paper. The feasibility of the approach has been experimentally verified with microstrip circuit prototypes. The filter produced a maximum passband loss of 1.7 dB and a third-order intercept point of $>$32 dBm with 35% tuning bandwidth.      

Dual-Band Bandpass Filter Design Using a Novel Feed Scheme

A planar dual-band bandpass filter based on a novel feed scheme is presented in this letter. The proposed filter employs two sets of resonators operating at diverse frequencies to generate two passbands. A novel scheme is introduced to feed the resonators. One set of resonators is utilized to not only generate the lower passband but also feed other resonators. Source-load coupling for upper passband is inherently realized. This scheme provides sufficient degrees of freedom to control the center frequencies and bandwidth of the two passbands. Four transmission zeros can be created close to passband edges, resulting in high skirt selectivity. To validate the proposed idea, a demonstration filter is implemented. The design methodology, filter sensitivity and experimental results are presented.      

Novel half-mode substrate integrated waveguide bandpass filters using semi-hexagonal resonators

In this paper, a novel bandpass filter is presented, designed, and implemented by using a triple mode semi-hexagonal Half-Mode Substrate Integrated Waveguide (HMSIW) cavity, which has the advantages of compact size, low insertion loss, and high selectivity in upper and lower passband. To realize a triple mode filter, the first resonant mode is shifted to near the next two modes using a via hole perturbation. Two microstrip open stubs connected to open edge of HMSIW resonator are introduced to generate two transmission zeros in the lower passband. The position of transmission zeros could be controlled by adjusting the coupling gap between the microstrip open stub resonators. By etching an E-shape slot on the top plate of HMSIW resonator, two other transmission zeros are produced in the upper passband. A wide-band planar six-pole bandpass filter, which has the advantages of wide bandwidth and small size, is also proposed and fabricated by cascading two triple mode resonators. Measured results indicate that 29% and 47% fractional bandwidth, as well as approximately 1 dB and 1.1 dB insertion loss, are achieved for the proposed filters. Measured results of all those filters agree well with the simulated results.     

A Narrowband Superconducting Filter Using Spirals With a Reversal in Winding Direction

A resonator consisting of a microstrip spiral, with a reversal in winding direction, is used for a narrowband superconducting filter. The fields are tightly confined, leading to the required small coupling coefficients, without a large separation between resonators. Nevertheless, tunability and power-handling capacity are better than some other resonators with localized fields. A quality factor exceeding a million was achieved. A 148 MHz, 0.1% bandwidth sixth-order quasi-elliptic filter is demonstrated     

宽阻带小型化双频带通滤波器

文中提出了一种具有宽阻带的紧凑型双频带通滤波器,它采用了折叠短路枝节负载谐振器、紧凑型微 带单元谐振器(CMRC)和阶跃阻抗谐振器结构。由于多个谐振器产生了五个可控传输零点(TZ),该滤波器实现了两个 通带之间的良好隔离度以及宽阻带特性。制作并测试了尺寸紧凑的双频带通滤波器实验样品,测试结果显示,第一通 带和第二通带的中心频率/ 插入损耗分别为0. 66 GHz/0. 8 dB 和1. 73 GHz/0. 7 dB,阻带频率高达10. 5 GHz,抑制水平 超过15 dB。     

一种基于互补谐振结构的宽带共模噪声滤波器

提出了一种用于高速差分信号传输的宽带共模噪声滤波器,采用在差分线正下方参考地平面上刻蚀内外互补的共面波导1/4波长谐振器和Z字形短路枝节线来实现。滤波器采用内外互补耦合λ/4开路枝节线谐振器结构,有效减小了横向尺寸,利用Z字形枝节线增大互感以改善滤波器的带内增益平坦度,最后用级联实现了共模噪声抑制阻带的展宽。仿真和测试结果表明,该滤波器在4.1~12.5 GHz频率范围内实现了20 dB的共模噪声抑制,共模阻带相对带宽(FBW)为101%,尺寸仅为0.78λ_g×0.18λ_g(15.8 mm×3.6 mm),其中λ_g为阻带中心频率处对应的波长。且该结构在实现共模噪声宽带抑制的同时,还可有效保证差分信号传输特性良好。     

Tunable Dielectric Resonator Bandpass Filter With Embedded MEMS Tuning Elements

This paper presents a novel approach for constructing a tunable dielectric resonator bandpass filter by using the microelectromechanical system (MEMS) technology. The tunability is achieved by unique MEMS tuning elements to perturb the electrical and magnetic fields surrounding the dielectric resonators. The use of such elements as a tuning mechanism results in a wide tuning range at a relatively low tuning voltage and fast tuning speed. A three-pole tunable dielectric resonator bandpass filter is designed, fabricated, and tested. The experimental filter has a center frequency of 15.6 GHz, a 1% relative bandwidth, and an unloaded Q of 1300. A tuning range of 400 MHz is obtained by using MEMS tuning elements with 2 mmtimes2 mm tuning disks. The measured results demonstrate the feasibility of the proposed concept     

Design of a Wide Stopband Microstrip Bandpass Filter With Asymmetric Resonators

In this letter, a novel microstrip bandpass filter (BPF) with asymmetric resonators is presented. With the asymmetric structure and capacitively loaded coupling, a wide bandwidth with sufficient rejection level can be achieved easily. A full-wave electromagnetic simulator IE3D is used, and the prototype of the BPF is fabricated and measured. Comparisons of simulated results and experimental data are shown; moreover, good match validates the proposed filter.     

COMPACT COUPLED LINEAR TAPERED LINE BANDPASS FILTER WITH TWO TRANSMISSION ZEROS

A new compact bandpass filter composed of two coupled linear tapered line resonators (LTLRs) is designed. The two resonators are arranged in different layers. The filter has two transmission zeros on both sides of the passband. It has small size and steep response below its passband. It is also shown that this filter has 0.6 dB low insertion loss at the centre frequency and 10.5% 3dB bandwidth.     

Compact Ultra-Wideband Microstrip/Coplanar Waveguide Bandpass Filter

A novel ultra wideband (UWB) bandpass filter is presented, using a compact coupled microstrip/coplanar waveguide (CPW) structure. The filter comprises of a single CPW quarter-wavelength resonator which is coupled to two microstrip open-circuited stubs on the other side of a common substrate. The two microstrip open-circuited stubs, which are about a quarter-wavelength long at the center frequency, can function as two resonators with associated coupling arrangement to the CPW. This forms a very compact three-pole filter. The proposed filter also exhibits a quasi-elliptic function response, with one finite-frequency transmission zero closer to each side of the passband. Thus, a high selectivity is achieved using a small number of resonators, which leads to low insertion loss and group delay across the passband. The performance is predicated using EM simulations and verified experimentally. The experimental filter shows a fractional bandwidth of 90% at a center frequency of 6.4GHz, with two observable transmission zeros (attenuation poles) at 1.95 and 10.36GHz, respectively. Furthermore, it has a very small size only amounting to 0.25 by 0.08 guided wavelength at the center frequency