The design and operation of practical charge-transfer transversal filters

Some of the design considerations for charge-transfer split-electrode transversal filters are discussed. Clock frequency, filter length, and chip area are important design parameters. The relationship of these parameters to filter performance and accuracy is described. Both random and tap weight quantization errors are considered, and the optimum filter length is related to tap weight error. A parallel charge-transfer channel, which balances both capacitance and background charge, and a coupling diffusion between split electrodes greatly improves accuracy. A one-phase clock is used to simplify the readout circuitry. Two off-chip readout circuits are described, and the performance of two low-pass filters using these readout circuits is given. Signal to noise ratios of 90 dB/kHz and an overall linearity of 60 dB have been achieved with this readout circuitry.     

Design of minimum-phase charge-transfer transversal filters

The interest of the minimum-phase charge-transfer transversal filters is pointed out in terms of sensitivity. When used in communication networks, such filters are indispensable for meeting the CCITT group-delay requirements. An experimental example for time-division multiplex equipment is described.     

Phase errors in transversal and recursive filters realised with charge-transfer devices

It is shown that nonideal amplitude transfer in charge-transfer devices can cause large phase errors in transversal and recursive filters using these elements.     

Minimum-phase CCD transversal filters

The calculated and measured response of a minimum-phase CCD low-pass transversal filter is compared to a linear-phase design with the same magnitude characteristics. It is shown that the minimum-phase design can offer up to an order of magnitude improvement in group delay, and is also less sensitive to transfer inefficiency and tap-weight error than the linear-phase design.     

Automatic equalization using transversal filters

The restriction that linear distortion imposes on the flow of information has been well known for some time. Consequently, means have been developed for reducing this distortion through the insertion of compensating linear devices. In the past this reduction has been achieved through the use of conventional lumped-parameter networks, quite static by nature. The use of the transversal filter, however, provides a more dynamic and flexible approach. This device is well suited to automatic and even adaptive operation, and thus it can meet the demands of a channel with time-varying distortion.     

Fast practical design of 2-D digital filters

This paper discusses a simple method for designing 2-D digital filters. The method can give linear phase 2-D filters with rather low computation cost, and can be generalized to multi-dimensional filtering applications. Examples are given to show its practicability. Northwest Telecommunication Engineering Institute     

High-frequency narrow-band single-mode fiber-optic transversal filters

A cascade synthesis procedure for constructing high frequency narrow-band (or high quality factor) single-mode optical fiber transversal filters usingj times j (j geq 2)bidirectional couplers is reported. Design and analysis of the cascade filters are described. Experimental results of many fabricated cascade filters with tap numbers up to 256 and the first-order passband frequencies up to 3.25 GHz are consistent with the mathematical analysis.     

Binary transversal filters with quantised coefficients

A binary transversal filter (b.t.f.) consists of a tapped shift register and a set of weighting resistors which determine its impulse response. B.T.F.s are discussed in which weighting coefficients are quantised, resulting in designs which are particularly suited to microcircuit implementation and digital programming of impulse responses. The precision to which frequency-response specifications may be made is determined as a function of the quantisation error. A number of possible applications are discussed.     

横向双模双频滤波器设计

基于横向滤波器耦合结构,采用支节加载双模谐振器,设计了中心频率位于1.57 GHz(GPS应用)与2.4GHz(WLAN应用)的双频微带滤波器。由短路支节加载双模谐振器形成第一个通带,开路支节加载双模谐振器形成第二个通带,两个谐振器被输入/输出馈线隔离,每个通带的中心频率与带宽可以单独调节。测试结果表明:两个通带内的最小插损分别为2.18,1.35 dB,3 dB带宽分别为5.2%,6.8%,回波损耗均小于16 dB,三个传输零点分别位于1.28,2.08,2.71 GHz处。该滤波器具有尺寸小、带外选择性好等优点。     

Distortion in rotating tap weight transversal filters

The distortion factors which presently limit the dynamic range and usability of transversal filters are described. In addition to fixed pattern noise and harmonic distortion, interaction noise due to rotation of the taps is found to be a major factor. The dynamic range of the device is analyzed and statistically estimated, with experimental verification.     

Yield modeling of acoustic charge transport transversal filters

This paper presents a yield model for acoustic charge transport transversal filters. This model differs from previous IC yield models in that it does not assume that individual failures of the nondestructive sensing taps necessarily cause a device failure. A redundancy in the number of taps included in the design is explained. Poisson statistics are used to describe the tap failures, weighted over a uniform defect density distribution. A representative design example is presented. The minimum number of taps needed to realize the filter is calculated, and tap weights for various numbers of redundant taps are calculated. The critical area for device failure is calculated for each level of redundancy. Yield is predicted for a range of defect densities and redundancies. To verify the model, a Monte Carlo simulation is performed on an equivalent circuit model of the device. The results of the yield model are then compared to the Monte Carlo simulation. Better than 95% agreement was obtained for the Poisson model with redundant taps ranging from 30% to 150% over the minimum     

面向运营的MPLS VPN网络设计研究

随着MPLS技术应用的普及,本文面向运营需要探讨MPLSVPN网络设计问题,首先对MPLSVPN技术实现模式进行对比分析,阐述BGP/MPLSVPN和L2MPLSVPN两种方式的技术特点,在此基础上,提出MPLSVPN路由及相关配置方案,并分别从链路连接、设备选择等方面阐述MPLSVPN网络部署方案,为MPLSVPN网络设计提供借鉴和参考。     

The design of fiber-optic filters

Fiber-optic filters can be used for processing wideband radio-frequency, microwave, and millimetric signals directly in the optical domain avoiding costly electrooptic and optoelectronic conversions. Because these filters sum signals on an intensity basis, they are bound to be positive and, hence, heavily restricted in their achievable performance. Nevertheless, such filters are the only choice because positivity is a consequence of the underlying physical mechanism. In this paper, the authors present a new design methodology to realize an arbitrary filter as a difference of two positive filters, thus overcoming any performance limitation     

Characterization of individual weights in transversal filters and application to CCDs

Time-domain sampling and averaging techniques for direct measurement of individual tap weights of transversal filters are considered. The essential features of the measurement and the corresponding instrumentation requirements are discussed from a general viewpoint; guidelines are determined for the implementation of measurement set-ups by using existing circuits and instruments. An application of the technique to the characterization of split-electrode CCD filters is then considered in detail and criteria for the analysis of experimental data are discussed. It is shown that separate evaluation of different sources of errors in the tap weights is possible. In particular, in the devices experimentally studied, three known error sources were quantitatively analyzed: charge-transfer inefficiency, mask misalignments, and uneven charge repartition. Application of the same techniques is also envisaged for the characterization of other CCD devices such as delay lines and imagers.     

Nonuniformly coupled microstrip transversal filters for analog signal processing

The Fourier transform relationship between frequency response and impedance profile for single nonuniform transmission lines is used to derive the time-domain step response of single and coupled nonuniform lines. The expression for the step response of a characteristically terminated nonuniformly coupled transmission line structure is shown to correspond to the characteristic impedance profile. By using this relationship, any arbitrary step response can be realizing by utilizing nonuniformly coupled strip or microstrip lines for possible applications as waveform-shaping networks and chirp filters. A numerical procedure to compute the step response of the nonuniform coupled line four-port is also formulated in terms of frequency-domain parameters of an equivalent cascaded uniform coupled line model with a large number of sections. Sinusoidal and chirp responses are presented as examples that are readily implemented using coupling microstrip structures. The step response of an experimental nonuniformly coupled microstrip structure is presented to validate the theoretical results.<>     

Modular and numerically stable fast transversal filters formultichannel and multiexperiment RLS

The authors present scalar implementations of multichannel and multiexperiment fast recursive least squares algorithms in transversal filter form, known as fast transversal filter (FTF) algorithms. By processing the different channels and/or experiments one at a time, the multichannel and/or multiexperiment algorithm decomposes into a set of intertwined single-channel single-experiment algorithms. For multichannel algorithms, the general case of possibly different filter orders in different channels is handled. Geometrically, this modular decomposition approach corresponds to a Gram-Schmidt orthogonalization of multiple error vectors. Algebraically, this technique corresponds to matrix triangularization of error covariance matrices and converts matrix operations into a regular set of scalar operations. Modular algorithm structures that are amenable to VLSI implementation on arrays of parallel processors naturally follow from the present approach. Numerically, the resulting algorithm benefits from the advantages of triangularization techniques in block processing     

Convolutional architectures for spectrum analysis employing CCD programmable transversal filters

Use of a Programmable analogue transversal filter, implemented as a monolithic charge-coupled device, as a basic signal processing element is presented. The application of such a device in waveform convolution is discussed and architectures which take advantnge of the programmable nature of the device are emphasized. Fourier transform algorithms which demand waveform convolution are shown to be efficiently realized with CCD technology and practical results are presented.     

A parallel binary structured LMS algorithm for transversal adaptive filters

The adaptation process in digital filters requires extensive calculation. This computation makes adaptation a slow and time consuming process. Simple, but versatile, parallel algorithms for adaptive filters, suitable for VLSI implementation, are in demand. In this paper a regular and modular parallel algorithm for an adaptive filter is presented. This parallel structure is based on the Gradient Vector Estimation Algorithm, which minimizes the Mean Square Error. In the parallel method, the tap weights of the adaptive filter are updated everys steps, whereas in the recursive algorithms, the tap weights are updated at each step. Fors step update, bit strings of lengths are used to derive the terms with which the tap weights of the adaptive filter are calculated. The algorithm presented computes the tap weights at timen+s as a function of the tap weights at timen, the inputs from timen+1 ton+s−1, and the desired output from timen+1 ton+s−1. The algorithm also can be mapped to a VLSI architecture that is both regular and modular and allows either expansion of the order of the filter or the degree of parallelism obtainable. A comparison between the performance of the sequential LMS algorithm, Fast Exact LMS algorithm, and the parallel binary structured LMS algorithm is presented.