具有混合反馈的高Q和/或高fs开关电容带通滤波器

本文提出了一种减少电容分布和总电容的高Q和/或高f_s开关电容(SC)带通滤波器。在传统的双二次SC滤波器结构中,引入部分正反馈并改变前馈网络可使总电容和电容分布得到大幅度的减少。举例说明了二阶高Q(=50)SC带通滤波器设计,并比较了不同滤波器结构的性能参数。     

Estimation of Aliasing Effects Due to Periodical Nonuniform Individual Sampling in High-Q Switched-Capacitor Filters

The periodical nonuniform individual sampling scheme has been shown suitable for capacitance spread and total capacitor area reduction in high quality (Q) factor switched-capacitor (SC) filters. However, the use of periodical nonuniform clock signals results in additional aliasing components in the output spectrum. This paper presents a simple model to analyze the generation of such alias components and gives practical expressions to estimate their power. The results are verified through circuit simulation of a 10.7-MHz second-order SC bandpass filter in a 0.35-mum CMOS technology. Implications on the use of this technique in the design of intermediate-frequency filters are discussed     

Accurate SI filters using RGC integrators

The design and implementation of single-ended and fully-differential switched current (SI) biquadratic high-Q bandpass filters to meet the specifications of the dual-tone multiple-frequency (DTMF) system are presented. Both designs use the regulated-gate cascode (RGC) dynamic current mirror to obtain center frequency accuracy of 0.1% and a quality factor of 24. Compared to the equivalent switched capacitor (SC) implementation of these filters, the single-ended SI filter requires 30% less area for the same minimum-sized capacitance, power dissipation and performance     

单一单位增益放大器的Q增强SC滤波器

本文阐述了采用单位增益放大器的SC滤波器的设计方法。基于无源Q增强技术,由Sallew Key有源RC电路导出了一系列Q增强的二阶SC低通、高通和带通滤波器。设计表明,本文提出的Q增强SC电路比文献给出的电路需要小得多的电容分散度。本文考察了这些电路灵敏度和有限GB对SC电路的影响。用分立元件做了实验,实验结果与理论计算相吻合。     

Economical design of SC coupled-biquad filters

The economic design of SC coupled-biquad bandpass filters can be improved using pairs of biquads with different types of bandpass functions, and by properly correcting the resulting phase error in each feedback loop.     

An integrated CMOS switched-capacitor bandpass filter based on N-path and frequency-sampling principles

A new combined switched-capacitor (SC) frequency-sampling N-path filter is presented, which allows the implementation of very narrow bandpass filters. The included frequency-sampling (FS) filter suppresses undesirable passbands of the SC N-path filter. The center frequency f/SUB m/ of the bandpass filter is identical to the circuit clock frequency f/SUB c/. Experimental results are presented for a CMOS SC frequency-sampling four-path filter with second-order filter cells, a center frequency of 1 kHz, and -3-dB passband bandwidth of 11.5 Hz.     

A CCD wave filter with low sensitivity

Starting with a double terminated Chebyshev LC ladder filter, a CCD wave filter has been implemented by using CCD resonators and charge amplifiers as basic building blocks. The bandpass filter which was realized on a test chip has a center frequency of 50 kHz, together with a relative Chebyshev bandwidth of 2.6 percent, 5 dB insertion loss, and more than 60 dB stopband attenuation. Compared to known SC filters, the advantages of the new approach are in extremely low sensitivity of the center frequency which is controlled by an external clock frequency, and a relative bandwidth which does not depend on the center frequency, but is controlled by capacitance ratios. Filter design, some aspects related to implementation, and experimental results are described.     

Passive CCD resonator filters

Novel passive recursive CCD bandpass filters have been realized using standard two-level-polysilicon gate NMOS technology. A Chebyshev bandpass (w/SUB rel,/ /SUB 3/ /SUB dB/=3.1 percent) and a fully integrated CCD signal filter with an extremely narrow 3 dB bandwidth of 97 Hz (Q=1350) at 131.85 kHz center frequency were implemented by means of cascaded CCD resonators. The latter chip contains the necessary clock generation and biasing circuitry realized with dynamic circuit techniques to achieve low power consumption (40 mW per filter). Performing all filtering operations exclusively in the charge domain ensures filter passivity. An extremely stable center frequency and a bandwidth independently controlled by a capacitance ratio are the special advantages of such filters.     

Design method for monolithic analogue filters

A new concept, compatible with m.o.s. or bipolar technology, for the design of monolithic analogue active filters is proposed. The method uses only ratioed capacitors as passive components and is especially suitable for the implementation of high-frequency filters. A high-Q, f0 = 1 MHz bandpass filter is presented as an example, using a total capacitance of only 58 pF.     

Novel switched-capacitor pseudo-N-path filter

The letter presents novel fully stray-insensitive switched-capacitor (SC) pseudo-N-path filters based on the theory of wave-flow networks. N-path filters are well suited for the realisation of narrowband bandpass and bandreject filters. The two main drawbacks of N-path filters, i.e. unwanted mirror frequencies due to path mismatch, and clock feedthrough located in the passband, are overcome by applying the pseudo-N-path principle. The design procedure will be demonstrated using an example of a 6-path filter based on a 3rd-order highpass prototype filter.     

Coaxial Bandpass Filter Design

A technique is described for synthesis of coaxial bandpass filters based on an improved design of impedance inverters. This technique is applicable to filters having bandwidths between approximately 1 percent and 20 percent of the center frequency. The inverter used to realize the filters is a section of either low-Z/sub 0/ line or high-Z/sub 0/ line and is synthesized as a distributed element rather than as a lumped shunt capacitance or lumped series inductance, respectively. Three methods of accommodating the discontinuity capacitance associated with an abrupt change in the characteristic impedance are reviewed. The first two methods are most useful for filters with a fractional bandwidth/spl gsim/ 10 percent and the third for a fractional bandwidths /spl lsim/10 percent. Numerical and experimental verification of the design procedure is provided.     

Compact Ultra-Wideband Bandpass Filters Using Composite Microstrip–Coplanar-Waveguide Structure

Compact ultra-wideband bandpass filters are proposed based on the composite microstrip–coplanar-waveguide (CPW) structure. In this study, the microstrip–CPW transitions and the CPW shorted stubs are adopted as quasi-lumped-circuit elements for realizing a three-pole high-pass filter prototype. By introducing a cross-coupled capacitance between input and output ports of this high-pass filter and suitably designing the transition stretch stubs, a compact three-pole ultra-wideband bandpass filter is implemented with two transmission zeros located close to the passband edges. To further improve the selectivity, two microstrip shorted stubs are added to implement a five-pole ultra-wideband bandpass filter with good out-of-band response. Being developed from the quasi-lumped elements, and not from the transmission lines, the proposed ultra-wideband filters have sizes more compact than those of the published wideband filters. The proposed ultra-wideband filters have the merits of compact size, flat group delay, good insertion/return loss, and good selectivity. Agreement between simulated and measured responses of these filters is demonstrated.     

A switched-capacitor preprocessor for speech recognition

A switched-capacitor (SC) preprocessing system (preprocessor) which extracts and emphasizes the local peaks of the spectrum in real time is proposed for speech recognition systems. Main components of the system are a specially designed bandpass filter bank, a low-pass decimation filter bank, two-dimensional local peak extraction (LPE) filters, and a LPE filter selection circuit. Furthermore, a SC cascaded integrator-comb filter design technique is proposed to realize the decimation low-pass filter and the LPE filter. Finally, the system is tested by using two speech recognition systems.     

Low-power CMOS continuous-time filters

A design technique for low-power continuous-time filters using digital CMOS technology is presented. The basic building block is a fully-balanced integrator with its unity-gain frequency determined by a small-signal transconductance and MOSFET gate capacitance. Integrator excess phase shift is reduced using balanced signal paths, and open-loop gain is increased using low-voltage cascode amplifiers. Two-pole bandpass and five-pole lowpass ladder filters have been implemented in a 1.2 μm n-well CMOS process. The lowpass prototypes provided 300 kHz-1000 kHz bias-current-tunable -3 dB bandwidth, 67 dB dynamic range with 1% total harmonic distortion (THD), and 30 μW/pole (300 kHz bandwidth) power dissipation with a 1.5 V supply; the bandpass prototypes had a tunable center frequency of 300 kHz-1000 kHz, Q of 8.5, and power dissipation of 75 μW/pole (525 kHz center frequency) from a 1.5 V supply. The active filter area was 0.1 mm²/pole for both designs     

Programmable CMOS switched-capacitor biquad using quasi-passivealgorithmic DAC's

This paper describes an electrically programmable switched-capacitor (SC) biquad using quasi-passive algorithmic digital-to-analog converters (DAC's). Since only two equal-valued capacitors are needed for programming each capacitance value, the proposed technique offers compact, cost-effective programmability when compared to traditional programming techniques employing binary-weighted capacitor-arrays (C-arrays). A demonstration prototype chip realized in a 1.2 μm CMOS double-metal double-poly technology, and which implements an 8 b programmable SC biquad giving a wide range of lowpass, bandpass and highpass filtering functions, occupies an active area of only 0.38 mm²     

Reduction of intermodulation distortion in microwave activebandpass filters-theory and experiments

This paper examines, both theoretically and experimentally, the dependency of the third-order intermodulation (IM) distortion and power saturation upon circuit and device parameters of an active bandpass filter using negative-resistance compensation. Nonlinear analysis is performed by means of the Volterra series formulation. We show that the IM distortion can be reduced by several orders of magnitude with suitable choice of external gate-source and feedback capacitance values. Measured performances of some 900-MHz experimental MESFET bandpass filters are presented     

Evolutionary-programming-based optimization of reduced-rank adaptive filters for reference generation in active power filters

We introduce an evolutionary-programming-based method for designing robust and computationally efficient adaptive bandpass filters. These predictive filters are optimized for generating current references in active power filters (APFs). The accuracy (phase/amplitude) of the reference current is crucial in current-injection-type systems, because it directly affects the harmonics reduction ability of the APF. Our digital filtering approach has the following advantages: selective bandpass response, efficient attenuation of specific harmonic components, capability to handle typical frequency alteration, small number of multiplications, and structural simplicity. In addition, practically no prior knowledge of the electricity distribution network and its loading characteristics is needed for designing the current reference generator. In an illustrative example, the total harmonic distortion of an artificial current waveform was reduced from 36.7% to less than 3.7% within the line frequency range 49-51 Hz. The proposed scheme is a combination of the hard-computing (HC)-type multiplicative general parameter method and evolutionary programming that, on the other hand, is a constituent of soft computing (SC). Such open-minded fusion thinking is emerging among researchers and engineers, and it can potentially lead to efficient combinations of HC and SC methodologies*both on the algorithm level and on the system level.     

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.     

HIGH SELECTIVITY SC BANDPASS FILTERS WITH LESS CAPACITOR SPREAD

Two novel switched-capacitor(SC)bandpass filters using a single operational am-plifier(op amp)are presented.Optimal designs for minimizing capacitor spread are also given.Gain-bandwidth product(GB)effects of op amps on the proposed SC circuits are taken intoconsideration.Comparisons with the proposed circuits and the circuits given by the literatureshow that the new circuits require less chip area in monolithic integration and are less sensitiveto the GB effects.     

T-cell SC integrator synthesises very large capacitance ratios

Very large pole/sampling-frequency ratios in SC filters require large capacitance ratios and thus result in inefficient area consumption. The use of a T-cell capacitance network allows one to integrate a very large time constant (VLT) integrator, which is, to the first order, insensitive to op-amp offset.