Showing papers on "Butterworth filter published in 1999"

A broad-band tunable CMOS channel-select filter for a low-IF wireless receiver

Abstract: Researchers agree that the active filter for channel-selection limits the dynamic range in a fully integrated wireless receiver, which uses no external components. This paper describes a filter designed for a wideband wireless LAN receiver operating in the 2.4-2.48 GHz ISM band. The receiver converts the desired channel to a low IF to enable on-chip rejection of the image. The analog filter must pass up to a 10 MHz wide single-channel centered after downconversion to IF ranging from 5 to 10 MHz. The classic requirements on all RF IC's apply to this filter, namely how to achieve the desired frequency response with the highest linearity and lowest noise at a given current consumption. For a channel-select filter, linearity is specified as out-of-band 3rd order intercept (IP3), to limit the in-band intermodulation from large interferers lying in the filter stop band. This work addresses the problem in filter architecture and circuit implementation. The achieved dynamic range surpasses all other published filter designs, except those cases where gain is favorably interleaved with filtering.

On the development of superconducting microstrip filters for mobile communications applications

Abstract: This paper presents recent developments of an eight-pole planar high-temperature superconducting (HTS) bandpass filter with a quasi-elliptic function response. A novel planar filter configuration that allows a pair of transmission zeros to be placed at the band edges is described. The miniature HTS filter has a fraction bandwidth less than 1% and is designed for mobile communication base-station applications to increase sensitivity and selectivity. Design considerations including filter characteristics, design approach, sensitivity analysis and unloaded quality factor of resonators are addressed. The filter was fabricated using double-sided YBCO thin film on an MgO substrate of size 0.3/spl times/22.5/spl times/39 mm. Very good experimental results were obtained with the filter cooled using liquid nitrogen. The minimum passband loss was measured to be approximately 1 dB. The passband width at points 1 dB down from the minimum loss point was 12.8 MHz for a center frequency of 1738.5 MHz. High selectivity was achieved with a 30-dB rejection bandwidth of 16 MHz.

A Procedure for the Automatic Determination of Filter Cutoff Frequency for the Processing of Biomechanical Data

Abstract: This article presents and evaluates a new procedure that automatically determines the cutoff frequency for the low-pass filtering of biomechanical data. The cutoff frequency was estimated by exploiting the properties of the autocorrelation function of white noise. The new procedure systematically varies the cutoff frequency of a Butterworth filter until the signal representing the difference between the filtered and unfiltered data is the best approximation to white noise as assessed using the autocorrelation function. The procedure was evaluated using signals generated from mathematical functions. Noise was added to these signals so mat they approximated signals arising from me analysis of human movement. The optimal cutoff frequency was computed by finding the cutoff frequency that gave me smallest difference between the estimated and true signal values. The new procedure produced similar cutoff frequencies and root mean square differences to me optimal values, for me zeroth, first and second derivative...

Narrow-band filter including sigma-delta modulator implemented in a programmable logic device

Abstract: A narrow-band bandpass filter is implemented in a field programmable gate array (FPGA). An analog-to-digital converter quantizes an input analog signal with a high degree of precision to produce input data samples. A sigma-delta modulator re-quantizes the samples with a substantially lower degree of precision. The re-quantized samples are passed through a bandpass, lowpass, or highpass, finite impulse response (FIR) filter which operates at the lower degree of precision. The reduced degree of precision enables a substantial reduction in the number of resources required to implement the narrow-band bandpass, lowpass, or highpass filter in the FPGA. The modulator includes a predictor filter which has a center frequency coinciding with that of the FIR filter, and redistributes noise such that it is lowest within the passband of the FIR filter. The narrow-band filter design can be adapted to incorporate a single or multi-rate decimator configuration.

Mode-coupling analysis of multipole symmetric resonant add/drop filters

Abstract: Time-dependent mode-coupling theory is used to analyze a type of resonant add/drop filter based on the excitation of degenerate symmetric and antisymmetric modes. Flat-top transfer functions are achieved with higher order filters that utilize multiple resonator pairs, designed to satisfy the degeneracy conditions. The resulting analytic expressions lead to an equivalent circuit and the transfer characteristics of the filter are related to standard L-C circuit designs.

Low-pass filters realizable as all-pass sums: design via a new flat delay filter

Abstract: This paper describes a new class of maximally flat low-pass recursive digital filters. The filters are realizable as a parallel sum of two all-pass filters, a structure for which low-complexity low-noise implementations exist. Note that, with the classical Butterworth filter of degree N which is retrieved as a special case, it is not possible to adjust the delay (or phase linearity). However, with the more general class of filters described in this paper, the adjustment of the delay becomes possible, and the tradeoff between the delay and the phase linearity can be chosen. The construction of these low-pass filters depends upon a new maximally flat delay all-pole filter, for which the degrees of flatness at /spl omega/=0 and /spl omega/=/spl pi/ are not necessarily equal. For the coefficients of this flat delay filter, an explicit solution is introduced, which also specializes to a previously known result.

Insensitive current-mode universal filter with minimum components using dual-output current conveyors

Abstract: A novel universal current-mode active filter with four inputs and one output is presented, which contains only three dual-output current conveyors. Two grounded capacitors and two grounded resistors. The circuit is very advantageous from an integration point of view. The proposed active filter realises all filter responses without any matching conditions at high impedance output and has low passive and active sensitivities.

Design of low-order linear-phase IIR filters via orthogonal projection

Abstract: This paper presents an indirect linear-phase IIR filter design technique based on a reduction of linear-phase FIR filters. The desired filter is obtained by minimizing the L/sub 2/ norm of the difference between the original FIR filter and the lower order IIR filter. We first establish a relationship between the Hankel singular values of the discarded part of the FIR filter and the L/sub 2/ norm of the corresponding filter approximation error based on model truncation. This result motivates us to propose a simple finite search method that will achieve better approximation results than commonly used truncation methods such as the balanced truncation (BT) and the impulse response gramian (IRG) methods. We then develop an iterative algorithm for finding an optimal IIR filter based on a matrix projection of the original FIR filter. The convergence of the proposed algorithm is established. Filters designed using the proposed algorithm are compared with those obtained by other techniques with respect to the amplitude response and group delay characteristics in the passband. Numerical examples show that the proposed algorithm offers the best performance.

High-Q optical microwave filter

Abstract: A new photonic signal processor topology is presented, which achieves high-Q value microwave bandpass filtering. It significantly increases the Q by means of a small free spectral range passive filter, while still operating the active stage with a large gain margin. The filter response demonstrates very high resolution microwave signal filtering with a measured Q value of 983.

High-speed recursive filter structures composed of identical all-pass subfilters for interpolation, decimation, and QMF banks with perfect magnitude reconstruction

Abstract: High-speed recursive filter structures for interpolation and decimation with factors of two, and quadrature mirror filter (QMF) banks with perfect magnitude reconstruction, are proposed. The structures are composed of identical all-pass subfilters that are interconnected via extra multipliers. For the case of interpolation and decimation filters, the overall transfer function corresponds in the simplest case to several half-band infinite-impulse response (IIR) filters in cascade. To achieve a smaller passband ripple than for a cascade design, a design procedure that has been used earlier for single-rate filters is used. In this approach, the design is split into designs of a prototype finite-impulse response (FIR) filter and a half-band IIR filter. For the case of QMF banks, the design is again separated into designs of a prototype FIR filter and a half-band IIR filter. One major advantage of the proposed filter structures over the corresponding conventional (half-band filter) structures is that the required coefficient word length for the all-pass filters is substantially reduced, implying that the maximal sample frequency can he substantially increased for a given VLSI technology. Further, for interpolation and decimation, the arithmetic complexity may be reduced in comparison with both the conventional structures and straightforward cascade structures. Simple recurrence formulas for computation of the interconnecting multipliers, given the overall transfer function, are derived. Several examples are included which compare the proposed structures with the corresponding conventional and straightforward cascade structures.

Bandpass filters with automatic tuning adjustment

Abstract: A method and system for tuning a tunable bandpass filter includes a bandpass filter having a passband which is dependant on the value of a tuning signal. A data signal having a dominant frequency component is applied to the filter and the power of the signal passed by the filter is determined. The tuning signal is adjusted until the passed power is maximized, indicating that the filter is tuned to the dominant frequency. The tuning signal can then be applied to other tunable circuits, including an oscillator having an output used as a clock signal to extract data from the data signal applied to the filter.

Digital implementation of a new type of hybrid filter with simplified control strategy

Abstract: A new type of hybrid active filter to compensate harmonics of a nonlinear load is presented in this paper. The proposed topology of hybrid filter combines a shunt passive filter (PF) and a shunt active filter (AF). A series inductor between both the filters is introduced to create a harmonic voltage source at the input of nonlinear load. A diode bridge rectifier with R-C load is considered as a nonlinear load. An indirect current controlled voltage source inverter (ICC-VSI) is considered as an AF. A simple control algorithm based on proportional plus integral control of a self-supporting DC bus voltage of the shunt AF is implemented on a TMS320C31 DSP. The passive filter is tuned to compensate 5/sup th/ and 7/sup th/ harmonics, while the AF compensates the rest of harmonics of the load current. A laboratory prototype model of the proposed hybrid filter is developed and its performance is examined. Experimental results are given and discussed.

An extension of pulse shaping filter theory

Abstract: The article presents a simple alternative approach to pulse shaping filters with ISI-free matched (white noise case) and unmatched filter properties. A Nyquist (1928) 1 filter in closed form is proved to be ISI-free with or without matched filtering when its complex transfer function is derived from an initially given Nyquist 1 filter. The simplicity of the application of this procedure is illustrated by an example.

Filter structures composed of all-pass and FIR filters for interpolation and decimation by a factor of two

Abstract: This paper introduces filter structures for interpolation and decimation by a factor of two. The structures are derived by using the frequency-response masking approach, in which the overall filter makes use of a periodic model filter, its complementary filter, and two masking filters. The periodic model filters are obtained by replacing each delay element in a model filter with M delay elements in cascade. The model filter is a half-band infinite-impulse response (IIR) filter composed of two all-pass filters in parallel, whereas the masking filters are linear-phase finite-impulse response (FIR) filters. In the final interpolator and decimator structures the filtering takes plate at the lowest of the two sampling rates involved. The corresponding overall filter can be designed by separately optimizing a half-band IIR filter and a linear-phase FIR filter. Both nonlinear-phase and approximately linear-phase filters are considered. One advantage of the proposed filter structures over conventional half-band IIR filter structures is that their maximal sample frequency is M times higher, which may be utilized to increase the speed in an implementation and/or to reduce the power consumption via power supply voltage scaling techniques. In the case of approximately linear-phase filters, the computational complexity can be reduced as well. Several design examples are included demonstrating the properties and advantages of the proposed filter structures.

Filter unit comprising a wideband bandpass filter and one band-elimination filter

Abstract: A filter unit comprises a wideband bandpass filter; at least one band-elimination filter having a stop band within the passband of the bandpass filter, so that the passband is divided into a plurality of pass bands by the stop band; and the wideband bandpass filter and the band-elimination filter being disposed in a single dielectric member. Since the passband of a wideband bandpass filter is divided into a plurality of pass bands by stop bands of one or more band-elimination filters, signals having frequencies corresponding to these divided pass bands are able to pass through the filter unit simultaneously.

A comparison of various low-pass filter architectures for sigma-delta demodulators

Abstract: A comparison of various low-pass filter architectures that are commonly used in Sigma-Delta(/spl Sigma/-/spl Delta/) demodulators is presented in the paper. In this comparison the conventional demodulator filter architectures such as the optimal FIR filter, Sinc/sup k/ filter and non-linear Zoomer filter are considered. It is shown that the optimum FIR filter provides the most attractive properties among the conventional demodulator low-pass filters. As an alternative to the optimal FIR filter, optimal Laguerre IIR filter architecture is then proposed in the paper. A design scheme for the optimal IIR filter is presented via the use of orthonormal Laguerre functions. In comparison with the conventional FIR filter approach, this design offers several attractive features. The proposed IIR filter design problem is easy to solve and numerically robust. Furthermore, the optimal IIR filter is easy to implement because it needs only a small number of components and therefore well suited for VLSI implementations.

A design of the novel coupled line low-pass filter with attenuation poles

Abstract: In this paper, a novel low-pass filter structure using coupled lines is proposed. The design formula is derived using the equivalent circuit of coupled transmission line. The proposed low-pass filter structure provides compact size, low insertion loss and two attenuation poles in the stop band. The higher order low-pass filters can be realized by using the proposed structure as a unit element. Experimental results show the validity of the proposed low-pass filter structure and the design method.

Fir filter utilizing programmable shifter

Abstract: A circuit arrangement and method utilize a programmable shifter (48, 88) coupled downstream of a multiplier (36, 86) to shift the product of an input value and a pre-scaled filter coefficient that implements a predetermined filter function. Through the judicious selection of an appropriate pre-scaled filter coefficient and a shift distance to shift the product, truncation errors associated with a digital implementation of a filter may be minimized, offering improved filter response compared to other discrete filter implementations with like coefficient resolution, or in the alternative, permitting acceptable filter response to be maintained with reduced coefficient resolution. Moreover, where the coefficient resolution is reduced, a filter may be implemented using relatively less space, less power consumption and less delay than in comparable conventional designs.

Filter bank constituting method and filter bank apparatus

Abstract: A method and apparatus for constructing a filter bank designed to split the frequency spectrum of digital signals into plural bands. Specifically, a low-pass analysis filter unit (H0(z)), adapted to pass frequency components of an input signal not higher than a pre-set frequency, is determined by a high-pass analysis filter unit (H1(z)) passing frequency components of the input signal not less than the pre-set frequency and a phase-linear filter unit (f(z)) having phase-linear characteristics. This enables efficient wavelet splitting of the input signal.

A tunable, video-frequency, low-power, single-amplifier biquadratic filter in CMOS

Abstract: In this paper, a tunable single-amplifier biquadratic lowpass filter is presented. It consists of one balanced low-gain current amplifier and a second-order MOSFET-C feedback network. The filter was integrated in a double-poly 0.6 /spl mu/m CMOS process and operates from a 3.3 V power supply. The pole frequency is tunable from 15.2 to 17.2 MHz, the pole Q is 3, the spurious-free dynamic range is at least 60 dB, and the filter consumes only 2.4 mW per pole. Furthermore, the active area used per pole is only 0.06 mm/sup 2/. The filter is well suited for low-power video-frequency applications, and demonstrates that the MOSFET-C filter technique can be applied successfully to filters other than those based on integrator-connected topologies.

High-q optical microwave processor using hybrid delay-line filters

Abstract: A hybrid active-passive signal bandpass filter comprising an active filter arranged in use to operate at a fundamental frequency which is a sub-multiple of a desired filter frequency of the bandpass filter; and a passive filter arranged in use to eliminate any pass bands in the frequency response of the active filter other than at the desired filter frequency for providing the pass band signal of the bandpass filter.

An inductorless active notch filter for RF image rejection

Abstract: A CMOS inductorless active notch filter is discussed and designed with the emphasis on low-noise, low-power, and gigahertz-range circuits suitable for portable wireless equipment. The proposed filter utilizes two Q-enhancement techniques to circumvent the low Q characteristics inherent in the simple feedback circuit. The frequency tuning is almost independent of Q tuning, facilitating the design of the automatic tuning circuitry. The stability of the filter is also further discussed. Simulations using 0.5 /spl mu/m CMOS technology demonstrate the feasibility of the tunable notch filter for DECT wireless applications. Simulation results show 4.17 dB voltage gain and 69 dB input dynamic range at a passband centered at 1900 MHz. The image signal suppression is 70 dB at 1482 MHz and the power consumption is 34 mW.

Programmable low-voltage continuous-time filter for audio applications

Abstract: The implementation of a continuous-time filter (CTF) useful for audio frequency applications is presented in this paper. The filter functions can be programmed and tuned with two independent control variables. The filter here proposed has been designed to work at 1.5 V of power supply and at a maximum of 0.5 /spl mu/A/OTA for the worst case current consumption. Electrical simulations of a Tow-Thomas biquad (TTB) show the possibility of obtaining low-pass and band-pass filter functions over the 10 Hz-40 kHz frequency range by changing a control current over four decades.

Switched capacitor filter circuit having reduced offsets and allowing for offset compensation without a closed feedback loop

Abstract: A switched capacitor filter circuit having reduced offsets and providing offset compensation when used in a closed feedback loop includes a chopper stabilized amplified filter circuit which amplifies and low pass filters its input data signal to produce an output signal with an out of band signal frequency component which is at the chop signal frequency and represents an offset and 1/f noise of the chopper stabilized amplified filter circuit. An output switched capacitor filter circuit which is synchronized with the chopper stabilized amplified filter circuit filters this signal with a stopband filter frequency response that virtually eliminates such out of band signal frequency component. The resulting output signal is then converted to a digital signal by an analog-to-digital conversion (ADC) circuit. This digital signal, generated as a result of this amplification, low pass filtering, stopband filtering and conversion by the chopper stabilized amplified filter circuit, output filter circuit and ADC circuit, respectively, includes a residual offset within one least significant bit (LSB) of the value of the digital output signal.

Variable-sample-rate delayless frequency-adaptive digital filter for synchronized signal acquisition and sampling

Abstract: In this paper, a hardware-based variable-sample-rate delayless frequency-adaptive cascaded digital filter is proposed. The open-loop frequency-adaptive and delayless property of a cascaded filter consisting of a median filter of length 3, a Blackman bandpass filter of length 30 and a predictive filter of length 25 is experimentally verified. Simulation results illustrating the filter's output response to input disturbances, in a synchronization signal acquisition application, are also presented.

A DSP active filter for power conditioning

Abstract: This paper presents a DSP controlled active filter for power conditioning, The active filter is designed to cancel lower order harmonics generated by nonlinear loads using a series resonant LC tank tuned to a high frequency along with a pulse-width modulation (PWM) rectifier topology. The PWM control of the active filter allows for independent control of lower order harmonics, both in amplitude and in phase, to efficiently cancel load generated harmonics for power quality improvement. The active filter control algorithm is simulated in Matlab and the harmonic cancellation process is verified through PSpice.

Parallel Butterworth and Chebyshev dip filters with applications to 3-D seismic migration

Abstract: Dip filtering is a necessary part of accurate frequency‐space domain migration, so design and application of reliable and efficient filters are of practical as well as theoretical importance. Frequency‐space domain dip filters are implemented using Butterworth and Chebyshev algorithms. By transforming the product terms of the filter transfer function into summations, a cascaded (serial) Butterworth or Chebyshev dip filter can be made parallel, which improves computational efficiency. For a given order of filter, the cost of the Butterworth and Chebyshev filters is the same. However, the Chebyshev filter has a sharper transition zone than that of a Butterworth filter with the same order, which makes it more effective for phase compensation than a Butterworth filter, but at the expense of some wavenumber‐dependent amplitude ripples. Both implementations have been incorporated into 3-D one‐way frequency‐space depth migration for evanescent energy removal and for phase compensation of splitting errors; a sing...

Technique for designing biorthogonal wavelet filters with an application to image compression

Abstract: A technique for designing new symmetric biorthogonal wavelets from a given symmetric regular filter is presented. The main idea is to find a symmetric complementary filter of a given regular filter such that it has the least mean square (LMS) amplitude deviation from the ideal halfband lowpass filter. New biorthogonal wavelet filter pairs can be obtained via factoring the product of the complementary polynomial and the given binomial. By applying these new symmetric biorthogonal wavelet filters to the compression of some complicated images an improved result in reducing artefacts may be achieved.

Bessel low pass filter in mixed planar waveguide techniques

Abstract: This paper describes the design and results of a Bessel low pass filter at 7.5 GHz for high speed (optical) communication applications. The equivalent circuit of a lumped element filter is transformed into a planar circuit mounted in a rectangular waveguide channel Each reactance of the filter is realized by an electrically short transm on line. To this end, a combianation of microstrip line and suspended stripline had to be used to cope with the widely varying impedance levels and to achieve a compact low loss filter.