Voltage-controlled filter

About: Voltage-controlled filter is a research topic. Over the lifetime, 5514 publications have been published within this topic receiving 70872 citations. The topic is also known as: VCF.

Electronically controlled high input and low output impedance voltage mode multifunction filter with grounded capacitors

Abstract: In this study, a three-input single-output voltage-mode biquadratic filter employing voltage differencing differential input buffered amplifier (VD-DIBA) is presented. The proposed filter uses two VD-DIBAs and two grounded capacitors without any external resistors, which is well suited for integrated circuit implementation. The circuit provides five standard transfer functions, namely, low pass, high pass, band pass, notch and all pass filters with electronic control of quality factor and pole frequency. Each transfer function can be selected by suitably selecting input signals via digital method. The filter does not require inverting of the input voltage signal. Moreover, the circuit possesses high input and low output impedances and thus it enables simple voltage-mode cascading. The PSPICE simulation and also experimental results are included, verifying the workability of the proposed filter. The given results agree well with the theoretical anticipation.

History and progress of the tow–thomas bi-quadratic filter part i: generation and op amp realizations

Abstract: The history of Tow–Thomas second-order filter is reviewed. Two alternative generation methods of the Tow–Thomas filter are discussed. The first is a generation method from the second-order passive RLC filter and the second is from the multiple feedbacks inverting low-pass filter using a single op amp. Several forms of the circuit are briefly reviewed. Passive and active compensation methods to improve the circuit performance for high-Q designs are summarized. Spice simulation results are included.

Cochlear filter bank with switched-capacitor circuits

Abstract: A parallel dilating-filters switched-capacitor filter bank is described in simulation of the cochlea. Area-saving is achieved by filter-sharing, effective sum-gain amplifier designs, and using area efficient nth-order filter designs, and in particular using a biquadratic filter design using charge-differencing. The structure is easily expandable to include more channels by extending with additional filters and output amplifiers, or by using several chips with different sampling frequencies in parallel connection. An offset-compensated area-efficient switched-capacitor sum-gain amplifier circuit design is described and can be used in the filter bank.

FIR filter design methodology for hardware optimized implementation

Abstract: This paper presents a novel method of FIR filter design for optimized hardware implementation. The FIR filters are extensively employed in a variety of consumer devices like TVs, mobile phones and docking stations. The optimized implementations of FIR filter furnish high quality signal processing at reasonable cost. The paper first analyzes the effects of quantization on frequency response of a filter by successively reducing the number of bits in each coefficient. Empirical analysis of coefficient quantization reveals a relationship between the number of bits, number of coefficients and the frequency response. The paper then presents a methodology for an optimized design of an FIR filter for hardware implementation. The proposed approach first designs a filter with certain parameters and then redesigns the same filter with tighter constraints resulting in higher filter order. The coefficients of the improved or over designed filter are then quantized successively with lesser number of bits by an iterative algorithm to a level where its frequency response matches to the original requirements. The synthesis results show that a significant reduction in hardware resources can be achieved using this methodology. The proposed approach has so far not been reported for reduction in hardware resources.

Design and evaluation of an active ripple filter with Rogowski-coil current sensing

Abstract: An active ripple filter is an electronic circuit which cancels or suppresses the ripple current and EMI generated by the power stage of a power converter, thus reducing the passive filtration requirements. This paper presents the design and evaluation of a feedforward active ripple filter which employs a Rogowski coil for ripple current sensing. The design of the active filter is discussed in detail, including the advantages, tradeoffs, and limitations of the approach. 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 can be achieved using the proposed active ripple filtering method.