Design of high-temperature superconducting low-pass filter forbroad-band harmonic rejection

A new type of low-pass filter based on a coupled line and transmission line theory is proposed for suppressing harmonics and spurious frequency. The seventh-order coupled-line low-pass filter with strip line configuration was fabricated using a high-temperature superconducting (HTS) thin film on MgO(100) substrate. The seventh-order low-pass filter has five attenuation poles in the stop band. Its cutoff frequency is 1 GHz with a 0.01-dB ripple level. The fabricated filter exhibits a characteristic stop band in the range from 1 to 7 GHz. A measured insertion loss at the pass-band of the HTS low-pass filter is 0.2 dB at 77 K, while the maximum return loss is 17.1 dB. These results match well with those obtained by the EM simulation. The new low-pass filter structure is shown to have attractive properties such as compact size, wide stop band range, and low insertion loss     

Variable Digital Filter With Group Delay Flatness Specification or Phase Constraints

In this paper, we consider the design of finite-impulse response variable digital filters (VDFs) with variable cutoff frequency or variable fractional delay. We propose the design of VDFs with minimum integral squared error and constraints on the maximum error deviation in conjunction with flatness group delay specification or phase constraints. These specifications allow the VDFs to have approximately linear phase, especially in the passband. As these specifications are required to be satisfied for all the filters generated by the VDF with controllable spectral characteristics, the linear constraints resulting from the flatness specification are relaxed to inequality constraints. To make the optimization problem tractable for the phase constrained problem, suitable approximations are employed in the paper. The design problem is formulated as an optimization problem with a quadratic cost function and infinite number of constraints. A numerical scheme with adaptive grid step size is proposed for solving the optimization problem.     

Design tables for two active RC circuits realizing low-pass polyonimic filters

Realization of RC-active filters, as proposed by Sallen and Key, consists of cascade connection of suitable second- and first-order building blocks. The paper presents design tables for two active RC circuits realizing low-pass polyonimic filters. The functions realized are of second to eighth-order low-pass Butterworth, Chebyshev (with 0.1, 0.5, 1, 2 and 3 dB ripple) and Bessel variety. This method uses simple op-amp integrator blocks and can equally be applied to both continuous-time and switch-capacitor filter designs. The advantages of this method are: simple method of designing LP filters from second to eighth order using integrator blocks (e.g. MAX 274 and MAX 275); low sensitivity to component values; low spread in component values; good tuning; can tune parameter f ₁ (cutoff frequency). The disadvantages of this method are: no independent adjustment of the cutoff frequency and the Q-factor; fixed gain of unity.     

All-inkjet-printed low-pass filters with adjustable cutoff frequency consisting of resistors,inductors and transistors for sensor applications

Low-cost and flexible first and second order low-pass filters with adjustable cutoff frequency were designed and printed by inkjet printing technology. The all-inkjet-printed low-pass filters were characterized and an adjustable cutoff frequency feature in form of an inkjet-printed organic thin-film transistors (OTFTs) was added to the filters for application-oriented fine-tuning. The applicability of these small circuits was evaluated by signal filtering for sensor applications. As a result, low-pass filters with an adjustable cutoff frequency ranging from 82 Hz to 740 Hz were obtained, demonstrating their suitability in signal filtering and their promising applicability for tactile sensing characterized by low frequency signals.     

基于树状分形结构的半模基片集成波导带通滤波器

提出了一种基于分形结构的半模基片集成波导(HMSIW)滤波器。该设计将树状分形结构蚀刻在HMSIW的上金属表面,通过在其高频端引入宽阻带来产生带通效应。这种基于树状分形的HMSIW带通滤波器结构,随着迭代次数的增加,其相对带宽基本保持不变(S11<-15dB),但其带通边缘频响斜度变陡,且带外抑制特性不断增强。仿真结果与实验结果基本吻合,较好地验证了设计的可行性和有效性。     

A low power 8th order elliptic low-pass filter for a CMMB tuner

This paper presents an 8th order active-RC elliptic low-pass filter（LPF） for a direct conversion China Mobile Multimedia Broadcasting（CMMB） tuner with a 1 or 4 MHz -3 dB cutoff frequency(f_-3dB).By using a novel gain-bandwidth-product（GBW） extension technique in designing the operational amplifiers（op-amps）, the proposed filter achieves 71 dB stop-band rejection at 1.7f_-3dB to meet the stringent CMMB adjacent channel rejection（ACR） specifications while dissipates only 2.8 mA/channel from a 3 V supply,its bias current can be further lowered to 2 mA/channel with only 0.5 dB peaking measured at the filter’s pass-band edge.Elaborated common-mode（CM） control circuits are applied to the filter op-amp to increase its common-mode rejection ratio （CMRR） and effectively reject the large signal common-mode interference.Measurement results show that the filter has 128 dBμV_rms in-band IIP3 and more than 80 dB passband CMRR.Fabricated in a 0.35-μm SiGe BiCMOS process,the proposed filter occupies a 1.19 mm² die area.     

Quasi-static design technique for MM-wave micromachined filterswith lumped elements and series stubs

This paper describes micromachined, membrane-supported low-pass and bandpass filters which are suitable for microwave and millimeter-wave (MM-wave) application. The designs are realized in coplanar-waveguide (CPW) form using short- and open-end series stubs with integrated metal-insulator-metal (MIM) capacitors, and are compact in lateral and longitudinal dimensions. A computationally efficient analysis has been developed for the design and characterization of the filters. The technique is based on a quasi-static coupled-line (CL) treatment of the series stubs, and uses normal mode impedance parameters, which are calculated with the spectral-domain approach (SDA). Due to the broad TEM-bandwidth of the membrane-supported transmission lines, the method can accurately predict filter responses well into the rejection band. To demonstrate the above claims, the measured and simulated S-parameters of a 0.3 mm ×2.2 mm low-pass filter with a cutoff frequency at 17 GHz, and a second passband at 115 GHz, are presented. The new approach is also used in the design of bandpass filters which exhibit 1.5-2-dB insertion loss and bandwidths around 10%     

Miniature and tunable millimeter-wave lowpass filter with MEMS switch

In this paper, fully monolithic tunable millimeter-wave filters with tapped-line feedings are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass filters were designed, fabricated, and tested. The cascaded CPW-based periodic structures, with low-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. The measured results of the reconfigurable low-pass filter show the 3-dB cutoff frequency change from 19 to 11 GHz with very small change in the average insertion loss from 1.3 to 1.9 dB. The chip size of the low-pass is 4.0 mm × 1.6 mm.     

Efficient implementation of tunable ladder filters using multi-output current controlled conveyors

A methodology to realize continuous-time current-mode tunable ladder filters of any order has been presented. This proposed technique individually simulates signal flow graph (SFG) of each branch element from passive filter prototype using only multi-output second generation current controlled conveyors (MCCCIIs) and grounded capacitors. This leads to simple structure, ease of design and suitability for IC fabrication. A third-order Butterworth low-pass filter, a third-order elliptic low-pass filter and a sixth-order Chebyshev band-pass filter are employed to demonstrate the proposed realization scheme. These simulated filters retain minimum requirement of passive and active elements and provide the filter corner frequency tunability. Moreover, the method allows an implementation of the elliptic filters by simply adding floating capacitors to all-pole filter structures.     

一种分数阶巴特沃斯滤波器的有源电路设计

本文将分数阶的低通滤波器的传递函数通式近似设计为Butterworth滤波器,在确定阶数与截止频率之后计算得到传递函数的系数.继而,本文通过该传递函数设计电路,进行仿真并电路实现.本文设计的电路在任意阶数下都只需要修改小部分元件便可得到预计截止频率,具有很强的灵活性,方便对比研究各阶分数滤波器.     

A CMOS transconductance-C filter technique for very highfrequencies

CMOS circuits for integrated analog filters at very high frequencies, based on transconductance-C integrators, are presented. First a differential transconductance element based on CMOS inverters is described. With this circuit a linear, tunable integrator for very-high-frequency integrated filters can be made. This integrator has good linearity properties and nondominant poles in the gigahertz range owing to the absence of internal nodes. The integrator has a tunable DC gain, resulting in a controllable integrator quality factor. Experimental results of a VHF CMOS transconductance-C low-pass filter realized in a 3-μm CMOS process are given. Both the cutoff frequency and the quality factors can be tuned. The cutoff frequency was tuned from 22 to 98 MHz and the measured filter response is very close to the ideal response of the passive prototype filter. Furthermore, a novel circuit for automatically tuning the quality factors of integrated filters built with these transconductors is described     

Sharp Cutoff Microwave Filters

A class of sharp cutoff filters using combinations of lumped constant and distributed constant reactance have been analyzed and a test made of one type. The filters are developed in accordance with image parameter theory and are m-derived. Both high-pass and low-pass types are analyzed. The improvements over previous sharp-cutoff image parameter filters are predictable band limits and more predictable response. The derivations hold for all frequencies and are not approximations good only for short lengths of distributed constant reactance. Also, this class of filters have much sharper cutoffs than can be obtained with an equivalent number of sections designed using modern network theory. Some of these filters have fairly flat response close to the sharp-cutoff and are useful as end-matching sections. Curves and design equations are presented for three types---two high-pass and one low-pass filter. A seven-section high-pass filter was designed and tested. Its cutoff rate was 87db in a 3 per cent bandwidth located in the 300-Mc region. The pass-band width was greater than 30 per cent.     

Optimal Design of 2D FIR Filters with Quadrantally Symmetric Properties Using Fractional Derivative Constraints

In this article, an optimal design of two-dimensional finite impulse response (2D FIR) filter with quadrantally even symmetric impulse response using fractional derivative constraints (FDCs) is presented. Firstly, design problem of 2D FIR filter is formulated as an optimization problem. Then, FDCs are imposed over the integral absolute error for designing of the quadrantally even symmetric impulse response filter. The optimized FDCs are applied over the prescribed frequency points. Next, the optimized filter impulse response coefficients are computed using a hybrid optimization technique, called hybrid particle swarm optimization and gravitational search algorithm (HPSO-GSA). Further, FDC values are also optimized such that flat passband and stopband frequency response is achieved and the absolute \(L_1\)-error is minimized. Finally, four design examples of 2D low-pass, high-pass, band-pass and band-stop filters are demonstrated to justify the design accuracy in terms of passband error, stopband error, maximum passband ripple, minimum stopband attenuation and execution time. Simulation results have been compared with the other optimization algorithms, such as real-coded genetic algorithm, particle swarm optimization and gravitational search algorithm. It is observed that HPSO-GSA gives improved results for 2D FIR-FDC filter design problem. In comparison with other existing techniques of 2D FIR filter design, the proposed method shows improved design accuracy and flexibility with varying values of FDCs.     

基于开路T型结构的小型化超宽阻带滤波器设计

传统滤波器由于寄生通带的存在,其高频阻带性能较差。随着超宽带雷达系统和超宽带通信系统的发展,小型化宽阻带的滤波器已成为一项紧迫的技术课题。该文论述了一种普适性的基于开路T型结构的小型化超宽阻带滤波器结构,这种滤波器和传统滤波器相比,结构极为紧凑,5倍基频范围内的寄生通带均被抑制,而通带性能保持良好。基于此结构实际制作了一个截止频率为2.9 GHz的低通滤波器,测量得到的通带内平均插入损耗仅0.67 dB,带内平均驻波比为1.33,过渡带陡峭,40 dB矩形系数仅1.096,而所测得的阻带从3.23 GHz到10.30 GHz之内谐波抑制大于36 dB,从10.30 GHz到15 GHz之内谐波抑制大于27 dB;该滤波器的长度仅为传统的同类型滤波器的长度的37.1%,面积大大减小。仿真和测量结果表明该类型滤波器同时满足了小型化和宽阻带的性能需求。     

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.      

A Novel Class of Generalized Chebyshev Low-Pass Prototype for Suspended Substrate Stripline Filters

A novel class of low-pass prototype filters having an equiripple passband response with three transmission zeros at infinity and the remainder at a finite real frequency is presented. The prototypes are synthesized using the alternating pole technique to obtain directly the even-mode or the odd-mode admittance and little accuracy is lost for prototypes up to degree 15. Tables of element values for commonly used specifications are included. The tables are useful for the design of TEM-mode microwave broad-band filters, diplexers, and multiplexers, particularly for a printed circuit form a realization. A design example of a low-pass microwave broad-band filter designed and constructed in suspended substrate stripline (SSS) configuration is given and experimental results are also presented.     

Hierarchical Web caching systems: modeling, design and experimental results

This paper aims at finding fundamental design principles for hierarchical Web caching. An analytical modeling technique is developed to characterize an uncooperative two-level hierarchical caching system where the least recently used (LRU) algorithm is locally run at each cache. With this modeling technique, we are able to identify a characteristic time for each cache, which plays a fundamental role in understanding the caching processes. In particular, a cache can be viewed roughly as a low-pass filter with its cutoff frequency equal to the inverse of the characteristic time. Documents with access frequencies lower than this cutoff frequency have good chances to pass through the cache without cache hits. This viewpoint enables us to take any branch of the cache tree as a tandem of low-pass filters at different cutoff frequencies, which further results in the finding of two fundamental design principles. Finally, to demonstrate how to use the principles to guide the caching algorithm design, we propose a cooperative hierarchical Web caching architecture based on these principles. Both model-based and real trace simulation studies show that the proposed cooperative architecture results in more than 50% memory saving and substantial central processing unit (CPU) power saving for the management and update of cache entries compared with the traditional uncooperative hierarchical caching architecture.     

基于MMIC工艺的片上射频LC无源滤波器

设计、制作了几种基于MMIC工艺的片上LC低通/带通滤波器并进行了测试. 测试结果表明,一个3nH的MMIC电感在6.8GHz下品质因数达到13.8,自谐振频率达到15.5GHz;制作的LC低通/带通滤波器的截止频率或中心频率与设计偏差很小,分别为2%和3.3%;低通滤波器在各自通带内的插入损耗小于3dB,带通滤波器在中心频率的插入损耗为7.2dB.     

Post-CMOS Compatible Micromachining Technique for On-Chip Passive RF Filter Circuits

This paper reports on a post-CMOS compatible micromachining technology for passive RF circuit integration. The micromachining technology combines the formation of high-performance microelectromechanical systems solenoid inductors and metal—insulator—metal (MIM) capacitors by using a post-CMOS process on standard CMOS substrate. Utilizing this process, novel on-chip 3-D configured RF filters for 5 GHz band are integrated on-chip. Two types of compact filters are designed and fabricated, with the layout size of the bandpass filter as 0.65 $,times,$0.67 ${rm mm}^{ 2}$ and that of the low-pass filter as 0.77$,{ times },$1.25 ${rm mm}^{ 2}$. From the measurement results, the fifth-order low-pass filter shows less than 1.06 dB insertion loss up to 5 GHz and ${-}{rm 1.5}~{rm dB}$ cutoff frequency at 5.3 GHz. The bandpass filter is a second-order coupled-resonator type, with measured 4.3 dB minimum insertion loss and better than 13 dB return loss in the pass band. Both simulation and shock testing results have shown that the filters are almost free of influence from environmental vibration and shock. From the measured results in various temperatures, the bandpass filters were found to show lower loss under low temperatures, while the passband shift is negligible in the various temperatures. Together with the fabricated filters, the developed micromachining technique has demonstrated the potential of on-chip integration and miniaturization of passive RF circuits.      

Differential current-mode tunable wave active filters based on single-ended wave port terminators

A method for the design of differential current-mode wave active filters, which is based on the use of single-ended wave port terminators, is presented in this paper. The resulting filters are modular and very simple to design while their cutoff frequency is controlled by a dc current, giving them the ability of frequency tuning. As an example a wide-band bandpass filter is realized by cascading a low-pass and a highpass filter. The overall filter has been integrated using a standard 0.35-/spl mu/m CMOS technology.