级联开关电流滤波器设计

本文提出了一种新的有源器件开关电流运算放大器(SIOA)。新元件的引入大大减化了电路的作图,十分便于开关电流(SI)电路的分析和综合。以开关电容(SC)电路为原型,导出了若干新的全极点和椭圆(二阶或三阶)SI电路。这些电路既可作为滤波节单独使用,也可用于级联设计以实现高阶转移函数。为了说明设计方法,给出了一个五阶SI低通滤波器设计例子。     

Architecture for low-voltage switched-current complex bandpassfilters

An architecture for the switched-current (SI) realisation of complex filters is presented, based upon the signal flow-graph method. Also briefly discussed is a practical design flow for SI complex filters, based on that for traditional real SI filter designs. A verification of the architecture is given via the design and simulation of a fifth-order complex SI bandpass filter with 1 MHz centre frequency and bandwidth, implemented using a low-voltage class AB neutralised SI scheme     

A NEW MULTIFUNCTION SWITCHED-CURRENT FILTER

A new switched-current(SI)biquadratic filter is presented which can simultaneouslyprovide the low-pass,high-pass and band-pass filters in a single building block.A symbol torepresent the universal SI integrator is also introduced.It can simplify the analysis and synthesisof SI networks.     

Analog wavelet transform using multiple-loop feedback switched-current filters and simulated annealing algorithms

A new approach for implementing continuous wavelet transform (CWT) based on multiple-loop feedback (MLF) switched-current (SI) filters and simulated annealing algorithms (SAA) is presented. First, the approximation function of wavelet bases is performed by employing SAA. This approach allows for the circuit implementation of any other wavelets. Then the wavelet filter whose impulse response is the wavelet approximation function is designed using MLF architectures, which is constructed with SI differentiators and multi-output cascade current source circuits. Finally, the CWT is implemented by controlling the clock frequency of wavelet filter banks. Simulation results of the proposed circuits and the filter banks show the advantages of such new designs.     

一种新的开关电流双二次滤波器

本文阐述了开关电流(SI)和开关电容(SC)电路的相似性原理,由此提出了一个新的SI双二次滤波器电路,该电路是由文献[5]的三运放SC双二次电路为原型导出的。该电路的一个重要特征是:它在单一积木块上能同时获得低通、带通和高通滤波功能。据此,得到了SI电路的一般双二次实现。     

开关电流梯形滤波器的双线性变换设计

本文提出了一种用双线性变换进行开关电流（ＳＩ）梯形滤波器设计的方法。该方法不经ＳＣ滤波器，而直接用提出的ＳＩ模块－双线性／差分（ＢｉＤ）积分器去精确模拟全极点及有限零点ＬＣ原型。从而使滤波器设计步骤及电路结构得到简化。     

A simple structure wavelet transform circuit employing function link neural networks and SI filters

Signal processing by means of analog circuits offers advantages from a power consumption viewpoint. Implementing wavelet transform (WT) using analog circuits is of great interest when low-power consumption becomes an important issue. In this article, a novel simple structure WT circuit in analog domain is presented by employing functional link neural network (FLNN) and switched-current (SI) filters. First, the wavelet base is approximated using FLNN algorithms for giving a filter transfer function that is suitable for simple structure WT circuit implementation. Next, the WT circuit is constructed with the wavelet filter bank, whose impulse response is the approximated wavelet and its dilations. The filter design that follows is based on a follow-the-leader feedback (FLF) structure with multiple output bilinear SI integrators and current mirrors as the main building blocks. SI filter is well suited for this application since the dilation constant across different scales of the transform can be precisely implemented and controlled by the clock frequency of the circuit with the same system architecture. Finally, to illustrate the design procedure, a seventh-order FLNN-approximated Gaussian wavelet is implemented as an example. Simulations have successfully verified that the designed simple structure WT circuit has low sensitivity, low-power consumption and litter effect to the imperfections.     

基于信号流图的开关电流滤波器设计

开关电流（SI）是有望取代开关电容（SC）的一种新型的取样数据技术，鉴于SC技术发展的成熟性及其与SI技术的紧密联系，即SC和SI滤波电路具有互易性，可采用信号流图转置的方法，将SC综合法直接用于SI滤波器设计，而无须提出新的设计方法。本文以二阶巴特沃思开关电容带通滤皮器为例给出了该方法的具体应用。     

Automated design of switched-current filters

This paper describes the automated design and synthesis of switched-current (SI) filters using SCADS, a flexible CAD system integrated in a major VLSI design suite. With this system, the nonspecialist can produce high performance analog filters suitable for mixed signal CMOS IC's fabricated using only standard digital processes. To achieve high levels of performance on silicon, filter designs are realized using an enhanced differential circuit technique (S²I) in its integrators and sample-and-hold cells. The design system is described in terms of the embedded circuits, its integrated tool set, the filter design flow and the engineering procedures for ensuring reliable circuit operation. Examples of high performance video frequency filters are presented, each generated automatically by SCADS within one day. Fabricated in a 0.8 μm standard CMOS process, they demonstrate state-of-the-art performance     

连续小波变换开关电流电路的实现

提出了一种用开关电流电路实现连续小波变换的方法,将连续小波变换转化为用带通滤波器组对信号进行处理,并用开关电流电路实现该带通滤波器组.文章采用基于第二代开关电流技术的带通滤波器组实现了8通道的Marr小波.仿真结果表明该滤波器组具有恒Q值,且每个带通滤波器的中心频率与理论值大致相符,从而证实了该方法的可行性.     

CMOS switched-current ladder filters

The design and implementation of switched-current (SI) ladder filters is described. The basic current-mode circuits, including the SI differential integrator/summer are developed. The SI integrator/summer is shown to be directly analogous to the switched-capacitor (SC) integrator/summer; thus, all the synthesis techniques developed for the design of SC filters can be used to synthesize SI filters. Signal flowgraph synthesis of SI ladder filters is presented. The nonideal characteristics of SI ladder filters that limit their accuracy are evaluated. Clock-feedthrough and device mismatch induced errors are more severe in the present SI circuit configurations than in SC circuits. A standard digital 2-μm n-well CMOS process has been used to implement two high-order ladder filters. Simulations accurately predict the measured results of the first integrated SI filters. The area and power dissipation are comparable to those obtained with the switched-capacitor technique     

基于改进差分进化算法的连续小波变换电路

提出一种基于改进差分进化算法和开关电流微分器的连续小波变换实现的新方法。引入混沌初始化种群、自适应变异和指数递增交叉概率因子,提高差分进化算法的收敛速度和精度,构造小波函数逼近模型,并利用改进差分进化算法,求得小波逼近函数及频域传递函数。采用开关电流微分器作为基本单元,设计冲激响应为小波逼近函数的开关电流滤波器组,通过调节小波滤波器的时间常数,获得多尺度小波函数,实现连续小波变换。实验结果表明该方法可行。     

Digitally programmable switched-current FIR filter for low-voltageapplications

In this paper, we describe a switched-current (SI) finite-impulse response (FIR) filter, suitable for equalizer architectures. The basic cell of the FIR filter is a SI sample-hold (S/H) circuit, appropriate for low-voltage operation. The programmability of the FIR filter structure is achieved via MOSFET-only current dividers. The FIR filter has been designed and implemented using a 0.8 μm CMOS process and operates at a power-supply voltage of 2 V     

Switched-Current Filters Revisited: Square-Root Domain Sampled-Data Filters

In this brief, the well-known switched-current (SI) filtering technique is revisited using the concept of the square-root domain (SRD) filtering. It is proved that SI filters are a subclass of the SRD filters, where sampled-data signal processing is performed. This is achieved by considering typical lossless and lossy SRD sampled-data integrator configurations, using a set of complementary SRD operators which are based on the quadratic I-V relationship of MOS transistor operated in the saturation. Circuit examples are given, where linear-domain integrator and third-order filter configurations were derived using appropriate SRD sampled-data building blocks     

Implicit functional testing of switched current filter based on fault signatures

This article aims at defining an efficient test strategy for switched-current (SI) circuit testing. By checking the constructed signatures (impulse response samples) against the derived tolerance ranges, we can infer the correctness of the device under test without explicitly measuring the original performance parameters. We also describe a technique of mapping the tolerance ranges in the performance space to its associated tolerance ranges in the signature space (We call such a procedure implicit functional testing). Taking into account the specificity of SI circuit, catastrophic and parametric fault model for testing are constructed. A fifth order Butterworth low-pass filter and a sixth order Elliptic band-pass filter have been used as test benches to assess the effectiveness of the proposed technique. Test results demonstrate that high fault coverage can be achieved with low cost test equipments.     

Realization of wavelet transform using switched-current filters

A method for realizing wavelet transform (WT) is presented, in which the WT is synthesized by a bank of switched-current (SI) filters whose impulse responses are the basic wavelet function and its dilations. SI circuits are well suitable for this application since the dilation constant across different scales of the transform can be precisely implemented and controlled by the sampling frequency. In this article, the wavelet base is approximated by a systematic algorithm with all the involved approximation parameters taken into account. Also, the SI filter employing the follow-the-leader feedback (FLF) multiple-loop feedback (MLF) structure is proposed to synthesize the approximation function. The Gaussian wavelet is selected as an example to illustrate the design procedure. Simulation results indicate that the proposed method has the merits of high approximation accuracy, strong stability and low sensitivity.     

A Current-to-Frequency Converter for Switched-Current Circuits

A current-to-frequency converter using switched-current (SI) circuits is proposed. The SI integrator with a hold-and-reset switch can control integration by the output signals. In the proposed circuit the oscillation frequency can be controlled by the input current, and the circuit is operated in the current domain. This is verified by HSPICE simulations.     

耦合二次节型开关电流带通滤波器的改进双线性设计

本文采用改进双线性变换，以一种新型双二次节为基块进行开关电流（ＳＩ）带通滤波器的设计。这种双二次节是用本文提出的双抽样方式ＳＩ改进型通用积分器构成的。文中介绍了耦合二次节型全极点及有限传输零点带通滤波器的设计方法。用该方法设计的ＳＩ滤波电路具有较好的高频特性，并能保持无源原型的低灵敏度特点。文中给出了Ｃｈｅｂｙｓｈｅｖ和Ｅｌｌｉｐｔｉｃ带通滤波器设计的实例。     

Analog Implementation of Wavelet Transform in Switched-Current Circuits with High Approximation Precision and Minimum Circuit Coefficients

This paper presents a novel procedure for analog implementation of wavelet transform in switched-current (SI) circuits. An improved hybrid PSO–SQP optimization is employed to precisely approximate the impulse response of a filter to the wavelet base function in time domain. The SI first- and second-order section circuits with minimum coefficients are designed based on infinite-impulse-response digital filter technology. Cascode techniques are occupied to reduce the effects of parasitic elements. Based on these SI first- and second-order section circuits, a parallel wavelet circuit structure is presented to synthesize the approximated wavelet base function. By adjusting the switch clock frequency, the wavelets at different scales can be realized. The Gaussian wavelet is selected as an example to illustrate the design procedure. Simulation results demonstrate the feasibility of the proposed procedure for analog wavelet transform in SI circuits.     

Analog VLSI implementation of wavelet transform using switched-current circuits

For applications requiring low-voltage low-power and real-time processing, a novel scheme for the VLSI implementation of wavelet transform (WT) using switched-current (SI) circuits is presented. SI circuits are well suited for these applications since the dilation constant across different scales of the transform can be implemented, and controlled by both the aspect-ratio of the transistors and the clock frequency. The quality of such implementation depends on the accuracy of the corresponding wavelet approximation. First, an optimized procedure based on differential evolution algorithm (DE) is applied to approximate the transfer function of a linear steady-state system whose impulse response is the required wavelet. The proposed approach significantly improves the accuracy of approximation wavelets. Next, the approximation of time-domain wavelet function is implemented by the SI analog filters. Finally, the design of the complete SI filter based on first-order and biquad section as main building block is detailed. Simulations demonstrate the performance of the proposed approach to analog WT implementation.