Showing papers on "Butterworth filter published in 1988"

A 4-MHz CMOS continuous-time filter with on-chip automatic tuning

Abstract: A third-order elliptic low-pass continuous-time filter with a 4-MHz cutoff frequency, integrated in a 3- mu m p-well CMOS process, is presented. The design procedure is based on the direct simulation of a doubly terminated LC ladder filter by capacitors and fully balanced, current-controlled transconductance amplifiers with extended linear range. The on-chip automatic tuning circuit uses a phase-locked loop implemented with an 8.5-MHz controlled oscillator that matches a specific two-integrator loop of the filter. The complete circuit features 70-dB dynamic range (THD >

Design of a 4-MHz analog integrated CMOS transconductance-C bandpass filter

Abstract: A continuous-time eighth-order fully integrated CMOS transconductance-C bandpass filter is presented for operation at 4 MHz with 800 kHz bandwidth and 0.5 dB pass-band ripple. A phase-locked loop for frequency tuning and four-point amplitude-locking loop for Q-factor tuning at the reflection zeros of the filter are implemented. The transfer characteristics were found to be essentially within specifications: less than 1-dB passband attenuation, 75-dB stopband attenuation and S/N ratio, and 0.5% harmonic distortion for 0.5-V/sub p-p/ signal were observed. Offset of the transconductances was internally controlled by an offset-control loop to less than 4 mV. A temperature-insensitive transconductance design and the noise characteristics of the filter building blocks are also discussed. >

Determination of the Optimum Filter Function for SPECT Imaging

Abstract: An observer study was performed in order to evaluate several filters used in SPECT imaging. The filters were applied to the simulated projection data of a uniform activity density cylinder which contained a cold, spherical lesion, 2 cm in diameter. The data incorporated the effects of the detector and scatter response functions, photon attenuation, and noise. Reconstructed transaxial images were used in 2AFC and ROC observer studies testing lesion detectability. In the 2AFC experiment, the Hanning filter scored lowest and did not show a optimum cutoff frequency. The Butterworth filter performed better and showed a well-defined optimum cutoff frequency at 0.15 cycles/pixel. The Metz filter performed as well as the optimum Butterworth but did not show an optimum power factor. In the ROC study, a high power Metz filter demonstrated an ROC curve of lower Az index and different shape from a lower power Metz filter and the optimum Butterworth filter.

Secondary LC filter analysis and design techniques for current-mode-controlled converters

Abstract: Small-signal characteristics of current-mode-controlled PWM converters with a second-stage LC filter are analyzed It is shown that a secondary filter can be designed to provide good attenuation of the switching ripple while maintaining adequate stability margins with capacitive loading The resonant frequencies and damping coefficients of the second filter are derived, and design guidelines are given It is shown that the current-loop gain of the buck converter is not affected by the addition of the second-stage filters when a small filter inductance is used Three design examples are presented to demonstrate the use of analysis results Two filter examples are designed for a buck converter One of the second filters shows the problems that arise with a poor design A third example is the design of a second-stage filter for a buck-boost converter In each of the design examples, the small-signal analysis was performed using EASY5 software and the circuits were simulated using the state-space simulation program COSMIR >

Refinements to the theory of error rates for narrow-band digital FM

Abstract: The bit-error-rate performance of narrowband digital FM with limiter-discriminator detection is considered for the cases of integrate and dump postdetection filtering with partial-bit integration, and sample-and-hold bit detection at the discriminator output. Error rate curves are presented for Gaussian, six-element Butterworth, and two-stage synchronously tuned IF filters. The calculations illustrate just how much more E/sub b//N/sub 0/ is required as the partial-bit integration time goes from 100% down to the limiting case of sample and hold. The results show that it is important to have a well-designed IF filter especially if the entire bit time is not available for detection. >

Optimum processing protocols for volume determination of the liver and spleen from SPECT imaging with technetium-99m sulfur colloid.

Abstract: A study of the effects of processing parameters on the determination of liver and spleen volume from SPECT data was performed A method for volume determination using a threshold algorithm was calibrated against phantoms and applied to 60 patient studies Good reproducibility was found using different projections and computing the volume on separate days Variations of the measured volumes with the threshold value, reconstruction filter cutoff frequency and attenuation correction were investigated Reconstruction parameters producing best image quality were also determined A threshold of 25% of the maximum value in the organ was determined from phantom studies Changes of 1% around this value yielded changes of 2–3% in the computed volume No significant change was noted as cutoff frequencies varied between 04 and 085 of Nyquist(0031 to 0066 cycles/cm)for a third order Butterworth filter Attenuation correction produced a decrease of 9% and 6% in liver and spleen measured volume respectively Best image quality was obtained with 04 Nyquist (0031 cycles/cm)cutoff frequency for third order Butterworth filter and attenuation correction It is concluded that optimal parameters must be determined for any processing protocol, and must then be adhered to in future applications to insure clinical accuracy, especially those parameters demonstrating the most quantitative and qualitative sensitivity

A low-pass notch filter for bioelectric signals

Abstract: Many bioelectric signals have relatively low-frequency content, but measurement devices are susceptible to power-line interference. The Type II Chebyshev low-pass filter can simultaneously perform the required low-pass filtering and removal of the narrowband interference. This filter has transfer-function zeros which result in zero gain (- infinity dB) at specific 'null' frequencies. A procedure for the low-pass filter design makes the first null frequency a design parameter so that the notch can occur at the interference frequency. >

On the design of a diplexer having Butterworth characteristics

Abstract: In a recent paper, V. Belevitch (see Int. J. Circuit Theory Appl., vol.15, no.1, p.51-60, 1987) discusses the design of a diplexer using filter pairs with Butterworth characteristics, where the separation of the desired frequency bands are accomplished by using filters connected either in parallel or in series. Instead of using complementary techniques to modify the ordinary filters, an analytical technique for the design of the diplexer is proposed. >

Digital anti-aliasing filter

Abstract: An original analog signal is supplied to A/D converter 2 through analog LPF 1. LPF 1 has a cutoff frequency of fa/2 (fa is the frequency of a clock pulse supplied to A/D converter 2). LPF 1 limits a frequency band determined by filter characteristics. An output from A/D converter 2 is supplied to sample circuit 4 through maximum filter 3. An output from sample circuit 4 is supplied to a circuit of the next stage as final output Dout. Maximum filter 3 can arbitrarily set the number of sampling interval data (filter width). Maximum filter 3 is a nonlinear filter for outputting a maximum value of input data within a set filter width as a representative value of the width. The clock pulse of frequency fa is also supplied to maximum filter 3 so that input/output operation of data is synchronized with the clock pulse. The filter width of maximum filter 3 is determined in accordance with fa/fb (fb is the frequency of a clock pulse supplied to sample circuit 4 , and fa≧fb).

A new modular VLSI filter architecture using computationally efficient recursive digital filter topology

Abstract: The authors introduce a modular VLSI architecture for a novel linear-phase FIR (finite impulse response) filter structure. The proposed linear-phase FIR filters have a highly reduced number of general multiplications per sample compared to conventional FIR filters. The novel filter structure is based on an IIR subfilter whose infinite impulse response is truncated into a finite one. Although the subfilter has a nonlinear phase response, it can be made exactly linear by reversing the data stream in time and using the same filter again. Another possibility is to use a maximum-phase version of the FIR filter in cascade. The choice between different realizations depends on the filter specifications. In the general case the filter coefficients cannot be represented with the simple shift-and-add procedure and the time reversal technique should be used. The authors prefer the maximum-phase FIR alternative. >

Electronically tunable band-stop filter

Abstract: The design procedures for an electronically tuned band-stop filter are presented. A technique for realizing tunable band-stop filters with coupled lines is discussed. The physical design and electrical performance of a five-section band-stop filter tunable from 6.5 GHz to 10 GHz, with a constant bandwidth, is given. The circuit required to drive the band-stop filter and the calibration procedures are described. >

The Corrugated-Waveguide Sand-Pass Filter - A New Type of Waveguide Filter

Abstract: A new type of waveguide band-pass filter has been realized by combining a corrugated low-pass structure and a high-pass configuration based on the cut-off effect. Low-pass and high-pass functions depend on each other. Therefore after an initial standard synthesis of both functions the overall filter geometry is optimized using an accurate CAD model to obtain the required band-pass response. The filter is especially suited for wide-band applications due to its good far out of band selectivity.

Analog front-end circuit for full-duplex communication

Abstract: In the high-group passband filter of an analog front-end circuit for full-duplex communications, switches enable an all-pass filter, a high-pass filter, and a low-pass filter to be connected in the optimum series for different band assignments, thus improving S/N performance.

Sigma-delta modulation adaptive digital filter

Abstract: A novel approach to the realization of an adaptive transversal filter without multipliers is presented. In the realization, a modified least-mean-square (LMS) algorithm is used for updating the filter coefficients. The input signal is encoded by a sigma-delta modulator, thus it eliminates the need for complicated analog-to-digital converters and requires no multipliers for any filter length. Computer simulations are included to confirm the convergence of the mean-squared error. Performances of the filter as adaptive noise canceller and adaptive line enhancer were also demonstrated by computer simulations. >

Adaptive nonlinear frequency domain filter with low phase loss

Abstract: A nonlinear frequency domain filter serving for the suppression of unwanted signals which are superposed on a wanted signal variable in a given frequency range. The frequency domain filter comprises linear transmission members and a dead-zone member. With the filter, the zero point of the dead-zone member, to which the input signal to be filtered is supplied, follows proportionally the output signal of a pass-band filter connected in parallel with the dead-zone member. Further, the output signal of the pass-band filter is added to the output signal of the dead-zone member.

GaAs MESFET switched-capacitor linear-median hybrid filter

Abstract: A novel median-type filter, the linear median hybrid (LMH) filter with switched-capacitor subfilters, is presented. In the LMH filter, median operation is applied to the outputs of a few linear subfilters. Thus the implementation of the LMH filter is simple as compared to a standard median filter with approximately the same noise attenuation. The circuit was implemented with GaAs MESFET technology. >

Adaptive parameter estimation for a constrained low-pass system

Abstract: A novel algorithm is presented for adaptive parameter estimation for a constrained low-pass Butterworth system model. The algorithm will estimate the system cutoff frequency and gain online. When it is known that the true system has a low-pass Butterworth structure or some transfer function similar to it and its true order is used, the algorithm will lead to a substantial savings in computation and more accurate results than unconstrained algorithms. Potential applications include filter design and adaptive decision on Nyquist rate for systems. >

Design of nearly perfect non uniform QMF filter banks

Abstract: A method to design nonuniform QMF (quadrature-modulation filter) filter banks is presented. The method is based on polyphase quadrature filter techniques, and extends previous works on uniform QMF filter bands. The theory of operation is presented, showing that the original signal decomposed into unequally spaced subbands can be reconstructed with negligible distortion. A computationally efficient implementation is proposed, and some examples are discussed, exhibiting interesting characteristics of the method. It can be applied to speech and high-quality sound coding. >

Error probability of offset differential phase shift keying with intersymbol and adjacent channel interference

Abstract: We compute the error probability for conventional and for symmetric differential phase shift keying (CDPSK and SDPSK) with differential detection in systems with binary, ternary and quaternary symbols and with two kinds of filters. In the first system the system response is a Butter-worth filter with two, three and four poles, which causes both intersymbol interference (ISI) and noise correlation which depend on the normalised 3 dB filter bandwidth B. In the second system the system response is a Nyquist filter with excess bandwidth s. In this system we consider both ISI caused by errors in sampling time and adjacent channel interference (ACI) caused by a signal in a neighbouring channel with frequency separation f A . We show that for B<1.0 binary and ternary SDPSK is better than CDPSK, while for quaternary symbols the difference is negligible. The difference is also negligible for B⩾1.0 for all symbols. For B<1.0 the lowest error probability is achieved in a system with second order filter. For the latter system with binary symbols, B=0.7, and a signal to noise ratio of 12 dB we show that the best phase offset is π/2 (hence SDPSK is the best offset DPSK) and that SDPSK is better than CDPSK with optimal (and unequal) decision regions. In the system with Nyquist filter SDPSK is either better or the same as CDPSK when ISI is taken into account, but the opposite is true when ACI is considered. However, in the latter case the difference is small.

A simple design method for transitional Butterworth-Chebyshev filters

Abstract: Some properties of the Transitional Butterworth—Chebyshev (TBC) filters are studied and a simple design method to obtain such filters is given. For a magnitude specification, the order of the transitional filter obtained will be the same as that of, or at most one higher than that of, the corresponding Chebyshev filter. In addition, the linearity of the phase response is improved.

Performance of CPM using a discriminator based data detector

Abstract: It is demonstrated that the error rate performance of continuous phase modulation (CPM), when detected using a limiter discriminator followed by a 2-bit integrate-and-dump filter (IDF), is far superior to the performance obtained using a discriminator followed by a 1-bit IDF The performance obtained at a modulation index h=1/2 is quite comparable to that of the 2-bit differentially coherent detector A parameterized performance study shows that drastic improvements are achievable by properly selecting the modulation index and simultaneously optimizing the receive filter bandwidth The investigation also shows that the error performance is sensitive to the type of IF filter response, ie, the Butterworth response yields superior performance in comparison to the Gaussian filter response >

Adaptive nonlinear filter using fractal geometry

Abstract: A new filter is described which uses fractal geometry in its synthesis. The important characteristic of the filter is that it allows some wanted high frequency parts of time series data to pass while rejecting other unwanted parts of the data.

A VLSI systolic filter with ternary coefficients for delta-modulated signals

Abstract: The realization of a digital FIR (finite impulse response) filter for both input data and coefficients encoded with ternary levels by delta-sigma modulation (DSM) is described. Due to the ternary values, multibit calculations are not needed. The filter architecture is very regular, highly parallel, and pipelines. The filter is easily made adaptive, as coefficients can be changed during normal operation. It is composed of bit-level systolic arrays whose cells are designed to allow a working frequency and consequently a throughput rate close to the limit of the technology used. A filter with 160 taps was realized in a 3- mu m H-CMOS technology. >

Satisfying the Haar condition in halfband FIR filter design

Abstract: A reformulation of the FIR symmetric halfband filter design problem is described that allows elimination of the constraints on coefficients from the design, thereby facilitating the direct use of the Parks-McClellan design procedure. In this procedure, it is only necessary to use a single-frequency care-band for approximation with about one-half the filter order of the halfband filter. >

A low-distortion anti-aliasing/smoothing filter for sampled data integrated circuits

Abstract: The theory, the practical design, and the measurement results of a simple low-distortion continuous-time filter are discussed. The filter harmonic distortion and attenuation performances comply with the echo-cancelling MODEM specification. The circuit was designed in a conventional 4- mu m p-well double-poly CMOS technology. Based on the Sallen and Key structure, the proposed configuration achieves a second-order Butterworth low-pass transfer function with a minimum silicon area and a low parametric sensitivity. >

Spatial-domain design of three terms separable denominator two-dimensional digital filters

Abstract: A two-dimensional (2-D) digital filter named a three-terms separable-denominator (3TSD) filter is considered and its spatial-domain design techniques are presented. The transfer function of the approximated filter is obtained by solving a set of bilinear equations iteratively. The 3TSD filter also offers some benefits as an SD filter. For example, the stability of the SD filter is easy to check and the filter is simple to implement. An example is presented to illustrate the utility of the proposed technique. >

Implementation of bit-serial recursive digital filters

Abstract: A single-chip digital filter capable of realizing a single class of transfer function with programmable cutoff frequencies, stopband attenuation, and passband ripple has been designed and implemented. The filter is implemented using a pipelined bit-serial two's-complement arithmetic architecture. Six different recursive digital filter structures were analyzed to determine the minimum signal and coefficient wordlengths required to obtain the same performance with each of the filters. This information was then used to estimate the maximum sample rate possible and the number of gates that would be required to implement each filter structure using the same gate array fabrication technology. The bilinear LDI digital filter chosen for implementation required the least gates for an architecture in which on pipelined bit-serial multiplier is shared throughout the filter. >

On the Memory Length of the Optimal Nonlinear Filter

Abstract: Consider the standard one-dimensional nonlinear filtering problem with plant diffusion coefficient eγ and observation noise coefficient e1-γ, stationarity of the plant is assumed. Definitions for the memory length of the optimal non-linear filter are suggested and it is shown that the memory length tends to zero as e → 0 for γ 1/2. It is pointed out that while for e → 0, γ 1/2 and an approximate asymptotically optimal non-linear filter is suggested for a particular generic example.