A design for the additional members of the transitional Mucromaf-Mucroer filters

The design technique for transitional Mucromaf-Mucroer filters is extended to cover the complete set of transitional members. It provides a designer with an extensive, tradeoff between the sensitivity performance and the selectivity characteristics for active filters.     

Transitional Butterworth-Cheby?shev filters

A class of transitional Butterworth-Cheby?shev filters is presented. The filters show gradual transition and, at the same time, maintain the equiripple peaks.     

Predistortion techniques for increasing the element tolerances in equiripple passband niters revisited

A well established technique to increase the element tolerances in the design of selective passive filters, or to decrease the adverse effect of limited gain-bandwidth product of operational amplifiers is to use transfer function with a special type of magnitude response for which the passband ripple amplitude decreases with increasing frequency. Recently various techniques have been reported to construct this type of filtering functions but they are either entirely numerical or, at least, require numerical optimization of some relevant parameters. In this paper, an exact method is proposed to find the explicit expression for the predistorted characteristic function of these filters applicable to both polynomial filters and filters with finite attenuation poles of any degree. The ratio of the magnitudes of the first passband ripple to the last passband ripple can be prescribed in advance, according to the required specifications.     

Design of active ripple filters for power circuits operating in the1-10 MHz range

A fundamental analysis of active ripple filters for powder circuits operating in 1-10 MHz range is presented. The improved understanding derived from this analysis allows filter circuits with gains five to ten times higher than previously reported to be built. Besides providing further reduction in the size of 1 MHz ripple filters, these higher gains make the active filters valuable for power circuit switching near 10 MHz     

基于CSD编码遗传算法的FIR滤波器优化设计

本文主要研究了采用CSD(canonic signed digit)编码的遗传算法对FIR(Finite Impulse Response)滤波器系数进行的有限精度优化,并对传统的CSD编码方法进行了改进,使之能够更快地收敛到最优解.针对CSD编码经过交叉、变异后可能出现的问题,提出了解码替代的解决方法.在级联滤波器的设计中,采用了波纹互相抵消技术使设计的级联滤波器通带内纹波大大降低.     

Active Filters for 1-MHz Power Circuits with Strct Input/Output Ripple Requirements

As the switching frequency of a dc-converter is raised from 100 kHz to 1 MHz, one would expect the energy storage elements of the circuit to be correspondingly reduced in size. If the circuit must meet input and output ripple requirements of the nature of MIL-STD-461B CEO3, however, the advantage of a higher switching frequency is significantly offset by the higher filter attenuation levels required. The use of active filters, in conjunction with minimal passive filters, to achieve the required ripple levels with a much smaller overall volume is discussed. Working active filters with gains in excess of 100 at 1 MHz are also presented.     

Analysis of Jitter Peaking Effects in Digital Long-Haul Transmission Systems Using SAW-Filter Retiming

The new lightwave long-haul transmission systems typically use surface-acoustic-wave (SAW) filters for timing recovery, in place of the phase-locked loops favored in slower systems. We report here analytical studies of jitter phenomena allowed by two kinds of filter ripple. The ripple is capable of causing jitter to accumulate exponentially with the number of regeneratorsNin a repeatered line. Such behavior is well known in the case of phase-locked-loop retiming, where the "jitter peaking" that usually appears in the loop response must be carefully limited to avoid exponential jitter growth. We show that equivalent phenomena can appear when the SAW filters exhibit passband ripple, or, as previously reported in condensed form, When ripple-free filters are detuned by approximately one-half the full 3 dB bandwidth. Furthermore, in the case of ripply filters, exponential jitter accumulation is found to be much more pronounced for random jitter than for systematic jitter. In addition, the alignment jitter within each regenerator can grow exponentially along the chain of regenerators. Neither of these statements is true in the case of the ripple-free filters previously treated in the literature.     

Nonrecursive digital filters with crescent ripple

The letter describes the results obtained on designing nonrecursive digital filters having crescent ripple. It is shown that the geometric mean of the maximum passband ripple and the maximum stopband ripple, when plotted against the normalized transition bandwidth, give a similar curve to that obtained for equiripple designs.     

Performance comparisons for nonrecursive digital filters with nonlinear phase characteristics

This letter presents a comparison between the performance, in terms of ripple and transition bandwidth, of nonrecursive digital filters with arbitrary phase characteristics and those with a linear phase response. Results are given which show that filters can be designed to have an arbitrary phase response, yet give as good a gain response as filters with linear phase.     

Transitional Murromaf?Murroer filters

A new class of lowpass filters with all transmission zeros at infinity, having equal-ripple behaviour in the passband, is described. The transfer function of these filters, referred to as transitional Murromaf-Murroer filters, is obtained by adding the multiple real poles and reducing the number of complex pole pairs to realise a lowpass RC active filter with a reduced number of amplifiers with respect to the classical transitional Butterworth-Cheby?shev filters.     

Transitional multiple-pole transfer functions for active-filter design

A new class of all-pole transfer functions for the design of RC active filters is described. The transfer functions of these filters, which can be referred to as transitional Mucromaf-Mucroer filters, are of higher degree than the previously described transitional Butterworth-Cheby?shev filters satisfying the same specifications, but provide much lower values of the critical pole Q-factor.     

Comparative performance of some polynomial-based lowpass filters for microwave/digital transmission applications

This paper reports on the comparative performances of some polynomial based lowpass filters in the lumped elements, microstrip and defected ground structure (DGS) environment. The microwave designers are normally familiar with Butterworth, Chebyshev and Bessel filters. However, many more polynomials based, ripple and non-ripple types LPF have been suggested for the low-frequency applications. Some of these LPF, such as L-opt, H-type, Transitional Butterworth-Legendre (TBL), Pascal, Legendre group of LPF, are compared for their applications in analog microwaves, digital transmission, efficiency enhancement of the linear power amplifiers and five level partial response modulations. A method is reported to compute the ripple frequency for the Legendre group of LPF and Pascal LPF. Further, a design is suggested to significantly improve group delay performance of high selectivity filters.     

Interpolated narrowband lowpass FIR filters

The article describes a class of digital filters, called interpolated finite impulse response (IFIR) filters that can implement narrowband lowpass FIR filter designs with a significantly reduced computational workload relative to traditional FIR filters. Topics discussed include: optimum expansion factor choice, number of FIR filter taps estimation, IFIR filter performance modeling, passband ripple considerations, implementation, and filter design.     

Method for designing recursive digital filters with short wordlength

With specified passband ripple, stopband ripple and cutoff frequencies, this method employs Crochiere's 2-parameter optimisation to equalise the passband and stopband statistical wordlengths before optimising coefficients in a multi-dimensional discrete space. Better design can be obtained by investing more computational time. This method is applicable to any recursive digital filters.     

Piezoelectric thin film unidirectional SAW transducer and filter

Small passband ripple piezoelectric thin film unidirectional transducers and filters are presented. ZnO thin film deposited on a fused silica was used in the experiment. As the result, the characteristics of no pass-band ripple and minimum insertion loss of 5.2 dB, and also the directionality of 22 to 29 dB per one transducer are obtained.     

Dynamic erbium-doped fiber amplifier based on active gainflattening with fiber acoustooptic tunable filters

We describe the first demonstration of a dynamic erbium-doped fiber amplifier (EDFA) based on automatic feedback control of active gain equalizing filters. The filters are all-fiber acoustooptic tunable filters capable of generating controllable filter shapes. Wide dynamic-range gain/power control is achieved with <0.6-dB signal ripple over 30 nm in various operating conditions. We also show, by numerical simulation, an important advantage of the dynamic EDFA over a conventional EDFA in cascaded structures     

广义切比雪夫型LC滤波器的设计*

提出一种广义切比雪夫型LC滤波器的设计方法,带外传输零点可以是任意设定,其带外特性既可以对称,也可以不对称.采用此方法设计出的LC滤波器,其带内波动可以与最大平坦型滤波器一样很小,而矩形系数可以与椭圆函数型滤波器一样好.每一个传输零点的位置可以由一个元器件的取值大小控制.与椭圆函数型LC滤波器相比,相同数量的元器件,它可以实现更陡的截止特性.     

Tables of Element Values for the Distributed Low-Pass Prototype Filter

An exact general synthesis for the distributed stepped-impedance low-pass prototype filter is presented here. Tables of values of the step impedances of filters having Chebyshev equal-ripple characteristics are given for up to 21 elements over a wide range of bandwidths and ripple levels. The tables are usefuf for the design of short-line low-pass filters, direct-coupled cavity filters, stepped-impedance acoustic or optical filters, impedance transformers, and branched guide directional couplers, as described in the papers of L. Young.     

Synthesis of spatial filters with Chebyshev characteristics

A spatial filtering technique using layered dielectrics for the reduction of antenna grating lobes or sidelobes is introduced and developed. The filters are used as a radome at the array face, and can be synthesized to have Chebyshev behavior in the spatial domain. Data are given for the design of two, three, and four layer filters with various spatial passband ranges and ripple levels.     

Design and evaluation of Feedforward Active ripple filters

An active ripple filter is an electronic circuit that cancels or suppresses the ripple current and electromagnetic interference generated by the power stage of a power converter, thus reducing the passive filtration requirements. This paper explores the design of feedforward active ripple filters for current ripple cancellation, including the design tradeoffs, advantages, and limitations of different implementation methods. The design and performance of an active filter using a novel Rogowski-coil current sensor is discussed in detail. Experimental results from a prototype converter system using this approach are presented, and quantitative comparisons are made between a hybrid passive/active filter and a purely passive filter. It is demonstrated that substantial improvements in filter mass and converter transient performance are achievable using this active ripple filtering method.