A Quasi-Elliptic Function Dual-Band Bandpass Filter Stacking Spiral-Shaped CPW Defected Ground Structure and Back-Side Coupled Strip Lines

A quasi-elliptic function dual-band bandpass filter (BPF) stacking spiral-shaped coplanar waveguide defected ground structure and back-side coupled strip lines is proposed, which allow two transmission paths to radio frequency signals. Each of them has quasi-elliptic characteristics and results in a respective passband. This can provide convenience to change one passband operating frequency independently of the other one. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed BPF. Theoretical and experimental results with good agreement are presented     

基于SIW技术的毫米波滤波器研究与设计

基于基片集成波导（substrate integrated waveguide,SIW）结构设计了两款四阶的耦合带通滤波器,使用三维全波电磁场仿真软件HFSS对设计的两款滤波器进行了仿真设计和优化.由仿真结果分析得出,两款滤波器的工作频率均位于毫米波频段.第一款SIW滤波器实现了切比雪夫型响应,中心频率为20 GHz,带宽为2 GHz,通带内的插入损耗低于1.5 dB,回波损耗低于-20 dB,在阻带中对信号的衰减程度可以达到50 dB.第二款SIW滤波器实现了准椭圆函数型的响应,中心频率为29.1 GHz,带宽为300 MHz,通带内的插入损耗低于1 dB,回波损耗低于-20 dB,在通带到阻带的过渡中实现了两个陷波点.仿真结果表明,在毫米波滤波器设计中引入SIW结构,有利于优化滤波器尺寸,得到较好的滤波器性能指标,是毫米波滤波器发展的一个重要方向.     

E-Plane Integrated Circuit Filters with Improved Stopband Attenuation (Short Papers)

Improved stopband attenuation is achieved by thick strips, by reduced waveguide sidewall dimensions, and by double planar integrated circuits. In contrast to thick strips which may cause high passband insertion losses and filters with reduced waveguide dimensions which require additional tapers, double planar E-plane integrated circuit filters combine the advantages of low costs, high stopband, and low passband insertion losses. Computer-aided design of a four-resonator Ka -band double metal insert filter achieves a calculated stopband attenuation between 40 and 60 GHz of more than 50 dB, the calculated minimum passband insertion loss is 0.43 dB (measured 1.8 dB). Higher order mode excitation and finite thicknesses of the inserts are included in the calculations.     

70 MHz surface-acoustic-wave resonator notch filter

A 70 MHz notch filter employing a surface-acoustic-wave resonator in a hybrid-coil circuit to produce a notch depth of 50 dB has been developed. The notch frequency is tunable over a 40 kHz range and the passband attenuation is approximately 7 dB.     

A high-frequency fifth order switched-current bilinear ellipticlowpass filter

Design considerations for and measured results of a prototype high-frequency fifth order switched-current bilinear elliptic lowpass filter are presented in this paper. The prototype filter was implemented on a standard 1.2 μm double-metal single-polysilicon CMOS process and occupied a total die area of 1.5 mm². When clocked at 2 MHz, the filter achieved a passband edge of 350 kHz, a stopband edge of 420 kHz, a passband ripple of 0.6 dB and a minimum stopband attenuation of 26 dB. With a single 5 V power supply the filter consumed 28 mW     

Quasi-Optical Low-Pass Filters Which Attenuate by Absorption

A type of filter structure is discussed which has application for quasi-optical systems using focused beams or oversized waveguide. The filter structure consists of a number of focusing reflectors which in the passband of the filter focus the energy from one reflector to the next so that the energy is beamed in a zig-zag fashion. However, the focusing reflectors are made from arrays of spaced-apart metal plates with the edges of the plates parallel to the E field. The focusing face of each reflector is thus formed by the front edges of the plates, When the frequency is suffcientIy high so that the spacing between the plates is greater than a half-wavelength, the energy passes between the plates and is absorbed by dissipative material placed therein. Thus above a certain frequency the reflectors are absorptive and a stopband is formed. A trial three-reflector structure was fabricated and tested with very encouraging results. The minimum loss points in the passband were about 1 dB, and the stopband was broad and free from spurious responses. There were 3- or 4-dB attenuation spikes in the passband due to "trapped modes," but it should be possible to eliminate these by improved mode launchers.     

Design of some 2-D filters through the transformation technique

The transformation technique is a powerful tool for designing 2-D FIR filters. However, it is not useful for the design of specially shaped filters with passband/stopband regions not centred around the origin. The authors extend this technique to design two types of filters. A notch filter has a stopband centred about a small region in the 2-D frequency plane. The authors propose an extension to the transformation technique with the windowing concept to achieve the design of notch filters. A directional filter has a passband extending fully along a straight line passing through the origin. The transformation technique is further extended to yield such directional filters. Design and application examples for both these filters are also presented     

High-resolution photonics-based interference suppression filter with wide passband

A new topology for a photonic signal processor, which overcomes the basic recursive frequency response problem that limits the passband range, is presented. The structure is based on a new multiple-wavelength offset-cavity structure that is cascaded with a series of unbalanced delay line structures. This not only can synthesize a very narrow notch response with good shape factor but also permits a multifold extension of the free spectral range (FSR) and passband width. Results on the interference mitigation filter demonstrate a stopband of 1% of center frequency and a fourfold increase in the FSR and passband width, while also having a very small shape factor, in excellent agreement with predictions.     

Classes of Sub-Miniature Microwave Printed Circuit Filters with Arbitrary Passband and Stopband Widths

Four new classes of microwave bandpass filters are defined herein. They are realized in triplate stripline and are exceedingly small devices as a result of using transmission line elements which are a quarter-wavelength well above the frequency of the passband. Each filter corresponds to a bandpass S-plane prototype which is derived using exact synthesis procedures from a specification of transmission zero locations. Passband and stopband widths may be independently specified and an extremely high degree of selectivity can be achieved when necessary. The slope of a filter skirt can he chosen to be such that 60 dB of attenuation is reached at a frequency < 3 percent from the comer of the passband.     

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。     

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.     

Design of nonrecursive digital filters with minimum phase

A method is described of transforming nonrecursive filters with equal-ripple attenuation in the passband, stopband and linear phase into those with minimum phase and half the degree, but again with equal-ripple attenuation in the passband and stopband.     

A new method for the design of IIR filters with flat magnitude response

This paper presents a new direct design of infinite-impulse response (IIR) filters with a flat magnitude response in both passband and stopband (Butterworth filters). The design specifications are passband and stopband frequencies and passband droop and stopband attenuation. The approach is based on an allpass filter with flatness at frequency points /spl omega/=0 and /spl omega/=/spl pi/. Depending on the parity of the IIR filter order, the allpass filter is either real or complex. However, in both cases, the resulting IIR filter is real.     

Sharp-Rejection Ultra-Wide Bandstop Filters

In this letter, a modified optimum bandstop filter (BSF) design is presented. Broad stopband and sharp rejection characteristics are achieved by realizing three transmission zeros near the passband edges. Stopband rejection depth and bandwidth can be controlled by the impedances of the configuration. A lossless transmission line model analysis is used to derive design equations. Further, a compact geometry is chosen by replacing the low impedance section with its equivalent dual-high impedance lines, which facilitates convenient folding. To validate the theoretical prediction, a single unit sharp-rejecting prototype BSF having a 20 dB rejection bandwidth of 126% at 1.5 GHz has been fabricated.      

Periodic stepped-impedance ring resonator (PSIRR) bandpass filter with a miniaturized area and desirable upper stopband characteristics

A periodic stepped-impedance ring resonator (PSIRR) is proposed to design dual-mode bandpass filters with a miniaturized area and desirable upper stopband characteristics. Design parameters of a PSIRR include impedance ratio R of the hi-Z to low-Z sections, their lengths, and number of impedance steps 2N. The resonant characteristics of PSIRRs with various N and R values are investigated by both the transmission-line theory and electromagnetic simulation. Proper choice of the above parameters leads to an optimal reduction of circuit area and extension of upper rejection bandwidth. Two extra transmission zeros exist in the upper stopband and are tunable via changing the arm lengths of the line-to-ring coupling structure. Realized by the standard microstrip technology, the dual-mode PSIRR bandpass filter has not only the first spurious response at higher than 3.7/spl times/ the passband frequency, but also an area reduction of better than 60% against a conventional ring filter. Experimental results of several fabricated circuits validate the analysis and theoretical prediction.     

Waveguide Sandwich Filters

A new class of waveguide filters is introduced, constructed from several thin plates sandwiched together. The combination of alternate plates having large and small rectangular apertures leads to a propagating structure which possesses a bandstop response and prescribed characteristic impedance. This basic element may be used as a simple compact bandstop filter, particularly where the main passband and stopband are well separated, such as in harmonic rejection. For filters with many stopbands, combinations of several waveguide sandwich filter elements are used to provide the main passband and the required attenuation characteristics in the prescribed stopbands. Although the filter is ideally suited for bandstop filtering due to its small size, low cost, low loss, and high power handling capability, additional applications to bandpass filtering and dispersive delay line operation are also cited.     

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.     

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.     

以ⅡR滤波器作补偿的CIC滤波器设计

为解决积分梳状(CIC)滤波器通带失真大和阻带衰减小对其应用的限制,在分析传统CIC滤波器幅频特性的基础上,给出一种用二阶ⅡR滤波器作为补偿滤波器级联CIC滤波器的改进方法。仿真结果表明,它与同级数规模的内插二阶多项式CIC滤波器、锐化CIC滤波器(SCIC)相比,通带和阻带的性能得到较大改善,实现复杂度较低。因此,它适用于对通带、阻带性能和实现复杂度要求较高的多采样率转换系统。     

Compact Elliptic-Function Low-Pass Filter Using Defected Ground Structure

A novel elliptic-function low-pass filter (LPF) is presented, which consists of a dumb-bell-shaped defected ground structure (DB-DGS), a spiral-shaped defected ground structure (SP-DGS) and a broadened microstrip line. The DB-DGS provides the required wideband attenuation in stopband, while the SP-DGS provides steep transition from passband to stopband. A 2.4 GHz five-pole LPF is developed and experimental results show that it has a sharp cutoff frequency response. The measured passband insertion-loss is below 0.3 dB, and the rejection band over 20 dB is from 2.95 to 8.25 GHz.