A reduced-size dual-mode bandpass filter with capacitively loaded open-loop arms

A novel type of dual-mode microstrip bandpass filter using degenerate modes of a dual-mode microstrip square loop resonator with capacitively loaded open-loop arms is proposed. Such a dual-mode bandpass filter with a 0.75% bandwidth at the center frequency of 1.603 GHz is designed and fabricated to demonstrate the design of reduced-size microstrip filters. It is shown that the proposed filter has a size reduction of about 59% at the same center frequency, as compared with the dual-mode bandpass filters such as microstrip patch, cross-slotted patch, square loop and ring resonator filter.     

Variable Bandpass Filters Using Varactor Diodes

A rectangular waveguide type variable bandpass filter for the 4-GHz bandpass has been proposed and tested. The bandpass width varies from 260 MHz to 1.02 GHz for a filter using varactor diodes. Two microstrip variable bandpass filters for the 6-GHz and 4-GHz bands are also proposed and tested. The passband width varies from 310 MHz to1.24 GHz for a varactor-diode coupled filter, and it varies from 380 MHz to 2.18 GHz for a filter which is composed of low-pass and high pass filters connected in cascade. The center frequency of the three filters can be changed arbitrarily.     

Ultra-Wideband Bandpass Filter Using Multilayer Liquid-Crystal-Polymer Technology

Novel ultra-wideband (UWB) bandpass filters are proposed based on quasi-lumped-element prototypes and implemented with multilayer liquid-crystal-polymer (LCP) technology. In this study, the broadside-coupled microstrip radial stubs and high-impedance microstrip lines are adopted as quasi-lumped elements for realizing compact UWB bandpass filters. By introducing a short-circuited high-impedance microstrip line as a shunt inductor and suitably designing quasi-lumped-element capacitors, a compact six-pole bandpass filter is implemented with the Federal Communications Commission (FCC) defined UWB specifications. To further improve the selectivity and wideband performance, an eight-pole filter of this type is developed by adding two shunt short-circuited microstrip stubs, which introduce a transmission zero at the upper passband edge. The proposed filters are fabricated using multilayer LCP technology. Good agreement between simulated and measured results of these filters are observed. The measured results show that the fabricated six-pole filter has good specifications for the FCC-defined UWB system. The fabricated eight-pole filter has an ultra-wide fractional bandwidth (139%) and a good stopband rejection level, which is higher than 38.1 dB from 10.57 to 18.0 GHz. The proposed filters are attractive for UWB communications and radar systems.      

集成宽带折叠半模基片集成波导带通滤波器

 本文提出并设计了一种新型的折叠半模基片集成波导（Folded Half-Mode Substrate Integrated Waveguide: FHMSIW）宽带带通滤波器,并给出了FHMSIW上层金属层槽缝式和中间金属层槽缝式宽带滤波器的仿真和测试结果。相对于半模基片集成波导（Half-Mode Substrate Integrated Waveguide: HMSIW）槽缝式滤波器,由双层PCB制作的FHMSIW槽缝式滤波器的尺寸减小了约一半。同时测试结果和仿真结果表明该宽带滤波器具有损耗小、带外抑制好等特性。     

Optimized E-plane bandpass filters with improved stopbandperformance

A computer-aided synthesis technique for E-plane bandpass filters with improved stopband performance is developed. An optimization procedure based on equal ripple optimization is adopted. The design of a symmetrical E-plane bandpass filter with improved stopband performance is considered; higher order mode interaction between E-plane discontinuities is included in the design. The predicted filter performance shows improved stopband performance and reduced filter dimensions compared with conventional E-plane bandpass filters. The validity of the method is confirmed by the measurement of a fabricated five resonator E-plane bandpass filter with improved stopband performance     

Design of Composite Right/Left-Handed Coplanar-Waveguide Bandpass and Dual-Passband Filters

The design and implementation of novel coplanar-waveguide (CPW) bandpass and dual-passband filters that consist of the composite right/left-handed short-circuited stubs are proposed. In contrast to the conventional short-circuited stub, whose input impedance repeats every half-wavelength, the composite right/left-handed CPW stub combines the phase-lead composite right/left-handed CPW and the phase-lag uniform CPW to achieve the arbitrary resonant frequencies with compact size. The equivalent bandpass and dual-passband LC resonators are established by investigating the frequency responses of the composite right/left-handed CPW stubs. The composite right/left-handed CPW bandpass filter is 62.5% more compact than the conventional quarter-wavelength shunt-stub CPW bandpass filter. The composite right/left-handed CPW dual-passband filter, which possesses the sharp rejection between the two asymmetric passbands, is also developed. The synthesis procedures of the composite right/left-handed CPW bandpass and dual-passband filters are successfully validated by measurement and full-wave simulation.     

EM based design of square-ring vialess bandpass filters

A simple technique for the design of new, vialess square-ring bandpass filters is presented. The proposed technique is based on the full-wave electromagnetic simulation of a single filter section with variable offset distance to realize a wide range of bandpass filters with flexible specifications at any given center frequency. The new, multilayered filter configurations are vialess in nature, taking advantage of the broadside coupling between different layers for simple fabrication. Two- and three-resonator Chebyshev bandpass filters with 20% and 10% bandwidth are designed at a center frequency of 2 GHz and the theoretical response is validated by measurement. Due to the EM based design approach, the proposed technique offers a high degree of accuracy. These new configurations are suitable for a variety of multilayered fabricational technologies.     

Bandpass filters using dual-mode and quad-mode Mobius resonators

Compact bandpass filters are being developed using Mobius wire-loaded cavity resonators. Initial results on tuned filters indicate that excellent filter characteristics can be attained in devices that are significantly smaller than traditional wire-loaded cavity technologies. A novel quad-mode Mobius resonator is presented which occupies the same volume as a dual-mode Mobius resonator. A four-pole bandpass filter is demonstrated using a single quad-mode Mobius resonator. Precisely controlled dielectric loading of dual-mode Mobius wire resonators has been implemented to realize bandpass filters. Two-pole and four-pole bandpass filters are demonstrated using one and two dual-mode dielectric-loaded Mobius resonators, respectively     

新型紧凑型带通滤波器的设计

文章设计了两个通带位于超宽带低频范围的带通滤波器,用一种T型结构来代替传统带通滤波器中的四分之一波长传输线,这种替代减小了滤波器的尺寸.而且,可以很方便的控制位于滤波器通带两端的传输零点,即合理的调节开路支线的电长度,进而可以方便的控制滤波器的通带范围.为了证明以上新型滤波器的优点,设计了两个开路支线电长度不同的带通滤...     

Microwave SAW bandpass filters for spacecraft applications

Microwave SAW bandpass filters for spacecraft applications are described. Two SAW bandpass filters were designed and fabricated in the 1.5 GHz band using temperature-stable ST-cut quartz substrates. The SAW bandpass filters were then assembled in a SAW filter bank. One unique feature of the SAW filter bank is that a broader band is available merely by adding the outputs of SAW bandpass filters adjacent in the frequency domain. Measured electrical responses as well as results of a transmission experiment show satisfactory performance. Effects of the temperature and aging stability characteristics are investigated based on the measured and calculated responses     

Compact Ultra-Wideband Bandpass Filters Using Composite Microstrip–Coplanar-Waveguide Structure

Compact ultra-wideband bandpass filters are proposed based on the composite microstrip–coplanar-waveguide (CPW) structure. In this study, the microstrip–CPW transitions and the CPW shorted stubs are adopted as quasi-lumped-circuit elements for realizing a three-pole high-pass filter prototype. By introducing a cross-coupled capacitance between input and output ports of this high-pass filter and suitably designing the transition stretch stubs, a compact three-pole ultra-wideband bandpass filter is implemented with two transmission zeros located close to the passband edges. To further improve the selectivity, two microstrip shorted stubs are added to implement a five-pole ultra-wideband bandpass filter with good out-of-band response. Being developed from the quasi-lumped elements, and not from the transmission lines, the proposed ultra-wideband filters have sizes more compact than those of the published wideband filters. The proposed ultra-wideband filters have the merits of compact size, flat group delay, good insertion/return loss, and good selectivity. Agreement between simulated and measured responses of these filters is demonstrated.     

Compact size and low insertion loss Chebyshev-function bandpassfilters using dual-mode patch resonators

A compact Chebyshev-function bandpass filter using dual-mode patch resonators is proposed. The filter presents 75% size reduction compared with the conventional Chebyshev bandpass filter using two square patch resonators. Because of inset feeding and only one coupling gap being required, the new filters can achieve a low insertion loss of 1.1 dB and reduce the fabrication uncertainties     

Elliptic-type bandpass filter and bandstop notch filter inspired by metamaterial NRI-TL topology

Compact and highly selective filters can be implemented by loading a transmission line with series printed capacitors and shunt resonant λ/4 stubs resembling the familiar printed negative-refractive-index transmission- line topology. Simulation and experimental results of a microstrip two-stage bandpass filter and a bandstop notch filter are presented. The four-pole bandpass filter exhibits an elliptic-type response with 3% fractional bandwidth. The microstrip bandstop notch filter exhibits a 50 dB deep stopband and a notch /spl varrho/ of 50. Both filters were designed at an operating frequency of 2.0 GHz.     

A Low-Power Programmable Bandpass Filter Section for Higher Order Filter Applications

We present a programmable, continuous-time bandpass filter that is extremely compact, power efficient, and can cover a wide range of frequencies (10 Hz-10 MHz). This capacitively coupled current conveyor (C ⁴) has a second-order bandpass transfer function and is capable of being used as a basic bandpass-filter element to create high-order filters. The use of floating-gate transistors helps to ease the difficulties of effectively utilizing G _m-C filters by providing precise, programmable current sources that set the filter's time constants. Additionally, we provide an algorithmic design approach for constructing these bandpass filters to meet any given specifications. This bandpass filter is ideally suited to large filter-bank applications because of its small size and low-power demands.     

LTCC宽边耦合交指型超宽带滤波器设计

提出用交指型结构实现超宽带（UWB）带通滤波器的小型化,并给出了设计方法。该结构通过宽边耦合实现超宽带滤波器需要的较大耦合系数,并通过加宽带状线谐振器的宽度减少不必要的交叉耦合,简化了滤波器的设计。最终设计了一个中心频率为f0,相对带宽为58%的六阶交指带通滤波器,滤波器尺寸仅为8 mm×11 mm。从仿真结果看,该滤波器保持了传统交指型滤波器阻带特性好,寄生通带远的优点。     

A reduced capacitor spread algorithm for elliptic bandpass SC filters

A modification of a well-known algorithm for simulating elliptic LC ladder filters by switched-capacitor (SC) technique is presented, The filter terminations were realized without damped integrators. The modification was proven useful in reducing the capacitance spread and total capacitance in high-Q bandpass SC filters: improvements by factors of five and six were obtained in the design of sixth- and tenth-order bandpass filters, respectively. A chip, including four sixth-order bandpass filters in the audio range, was designed and found to function properly.     

Application of Dual TM Modesto Triple- and Quadruple-Mode Filters

The cylindrical cavity dual orthogonal transverse magnetic (TM) mode is introduced as a basic building block for the realization of microwave multiple-coupled-cavity bandpass filters. This concept is shown to offer significant advantages in the design of triple-mode filters and permits the design of the new quadruple-mode filter. Experimental verification is provided by the realization of a triple-mode, six-pole elliptic function bandpass filter with dual TM/sub 110/ and single TE/sub 211/ (transverse electric) modes and a quadruple-mode, eight-pole bandpass filter with dual TM/sub 110/ and dual TE/sub 112/ mode cavities. All units exhibit good agreement between theory and experiment.     

Narrow-bandpass filtering with modulation

To overcome the problems of carrier leak etc. experienced with N-path filters incorporating active lowpass filters, it has been suggested that N-path filters incorporating bandpass filters (which must be well matched) be used to produce a pair of passbands away from the carrier frequency, with another filter at the required final frequency to discriminate between the wanted and the image passbands. An alternative and practical solution is described here in which neither the well matched low-frequency filters nor the additional high-frequency filter are required; instead a single low-frequency bandpass filter and two pairs of elementary phase-shift networks are used. The circuit is well suited to realisation as a thin-film or hybrid integrated circuit, since all the frequency-selective circuits operate at the low frequency.     

Design techniques for tunable transresistance-C VHF bandpassfilters

In this paper, a tunable wideband linear transresistance (R_m ) amplifier is proposed and analyzed. Using the tunable R_m amplifier, a new transresistance-capacitor (R_m-C) differentiator is designed. Considering the intrinsic capacitances of the MOS transistors as filter elements, this R_m-C configuration can he regarded as a very high frequency (VHF) bandpass biquadratic filter. The proposed biquad has a simple structure and thus occupies a small chip area and consumes little power. Moreover, higher-order VHF bandpass filters can be realized by directly cascading the biquads. Experimental results have successfully proven the capability of the proposed new filter implementation method in realizing VHF bandpass filters with the center frequency higher than 100 MHz when C_d=1 pF. The deviations of the measured center frequency f _o and quality factor Q of the fabricated bandpass filter from the simulated results are less than 8%. The deviation of the center frequency can be post-tuned by adjusting the control voltages V_CN and V_CP of the tunable R_m amplifier. With 1 pF differentiating capacitor, the center frequency of the fabricated VHF R_m-C bandpass filters can be tuned in a wide range larger than 30 MHz. The measured maximum signal level is 25 mV_rms and the dynamic range is 47 dB. The chip area is 0.05 mm² and power consumption is 5.05 mW with ±2.5 V power supply     

Slow-wave bandpass filters using ring or stepped-impedance hairpinresonators

This paper proposes a new class of slow-wave bandpass filters that uses a microstrip line periodically loaded with microstrip ring or stepped-impedance hairpin resonators. The new slow-wave periodic structures utilize the parallel and series resonance characteristics of the resonators to construct a bandpass filter. Unlike conventional slow-wave filters, the proposed bandpass filters are designed to produce a narrow passband at the fundamental mode of the resonators. The new filters provide lower insertion loss than that of parallel- or cross-coupled ring and stepped-impedance hairpin bandpass filters. The calculated frequency responses of the filters agree well with experiments