Showing papers on "Butterworth filter published in 1975"

Programmable general purpose analog filter

Abstract: A programmable transversal filter employig two charge transfer delay lines one for sampling a reference function, the samples providing the weighting factors for the transversal filter; the other for sampling an input signal to the filter. Each sample of the input signal is then multiplied by the appropriate weighting factor obtained from the sampling of the reference signal and all products are summed to obtain a sample of the filter output.

Bidirectional constant impedance low pass/high pass filter circuit

Abstract: A bidirectional filter circuit having an input and an output and substantly constant input and output impedance characteristics over the desired frequency range. A low-pass filter network is connected between filter input and output and has identical low-pass filter half sections cascaded back-to-back with a symmetrical all-pass network interposed therebetween, the all-pass network providing isolation between the low-pass filter half sections and the desired terminating impedance therefor. First and second identical compensating networks are respectively connected to the filter input and output and have reciprocal characteristic functions with respect to the low-pass filter half sections to compensate for impedance changes in the low-pass filter half sections over the desired frequency range without affecting amplitude characteristics thereof. A high-pass filter network is connected between filter input and output and has identical high-pass filter half sections cascaded back-to-back with a symmetrical all-pass network interposed therebetween, the all-pass network providing isolation between the high-pass filter half sections and the desired terminating impedance therefor. Third and fourth identical compensating networks are respectively connected to the filter input and output and have reciprocal characteristic functions with respect to the high-pass filter half sections to compensate for impedance changes in the high-pass filter half sections over the desired frequency range without affecting amplitude characteristics thereof.

Band pass filter circuit with automatic bandwidth adjust

Abstract: Band pass filter circuit for a band pass filter which detects a phase difference between input and output signals of said band pass filter, and the detected output controls, via a low pass filter, a voltage controlled oscillator, the output of which controls first and second mixers connected respectively to an input side and an output side of the band pass filter, so that the output of the first mixer can be maintained at the center frequency of said band pass filter. Further, when an irregularly timed signal is received, before an input signal is pulled in the synchronized state, said band pass filter is provided with a wide pass band so as to pull the signal in the synchronized state in rapidly. After said input signal is pulled in said center frequency, the pass band of said band pass filter is changed to a narrow bandwidth so as to improve the quality of the noise and at the same time, a cutoff frequency of said low pass filter is changed to a lower frequency side so as to improve the stability of the band pass filter circuit.

An analysis of quantization error in digital filters based on interval algebras

Abstract: Interval algebras are introduced as media in which to simulate digital filters for the purpose of analyzing quantization effects due to finite wordlength. The theory presented forms the basis of a computer-aided analysis scheme which generates confidence interval error bounds on the time domain response of a digital filter. The techniques are applicable to filters of arbitrary order and configuration implemented in either fixed or floating-point arithmetic. Experimental data is presented for a fourth-order low-pass Butterworth filter realized with fixed-point arithmetic in the direct, canonical direct, parallel, cascade, and ladder configurations. An example of Parker and Hess is used to illustrate the bounding limit cycles with interval techniques.

Spatial recursive filter design via rational Chebyshev approximation

Abstract: The computer implementation of a numerical algorithm for obtaining rational approximations is discussed. This method offers the promise of a comprehensive solution to the problems of two-dimensional recursive digital filter design. Combination of this technique with an easily implemented stability test avoids current stability problems in present methods and places no restrictions as to type on filters that may be designed. Both one- and two-dimensional filters may be designed with this technique.

Wide-Band Frequency-Shift Keyed Receiver Performance in the Presence of Intersymbol Interference

Abstract: The noncoherent binary frequency-shift keyed (FSK) receiver analyzed in this concise paper employs predetection filters with bandwidths much larger than the symbol rate. Wide-band predetection filtering is used in order to trade performance for simplicity and reduced costs. In this analysis bit-error rate (BER) degradation due to wide predetection filter bandwidths and intersymbol interference caused by postdetection filtering is determined. The postdetection filters considered are single-pole RC and two-pole Butterworth filters. The receiver performance using these filters is compared with the performance achieved when using integrate-and-dump postdetection filtering. Experimental and simulation results are presented which agree well with the analysis.

Active filter with inverse option

Abstract: An electronic filter circuit comprised of summing circuits and integrating circuits is interconnected such that the filter may use the same components to serve either as a band-reject or a band-pass filter having the same natural frequency. Changing of the filter operation between the two modes is accomplished simply by the interchange of two component values.

Class of optimum spatial filters

Abstract: A new class of optimum spatial filters is developed. This class is optimum for filters with a magnitude constraint on the filter transfer function. Some special cases of this class are found to be similar to the Wiener filter, matched filter, and probability-weighted spatial filter. The derivation of the probability-weighted spatial filter is extended to include complex-valued signals.

A tunable filter using amplifier pole

Abstract: A circuit consisting of two periodically operated switches, potentiometers, resistors, and compensated operational amplifiers, but not containing external capacitors, is proposed for the realization of a second-order bandpass and low-pass filter. The filter is electronically tunable and the natural frequency of the filter varies linearly with the width of the pulses controlling the FET switches.

Electromechanical branching filter

Abstract: An electromechanical branching filter capable of branching an input electrical signal into two output signals having different frequency components. It includes a wide bandpass filter section and a narrow bandpass filter section, both sections being mechanically connected to a common input transducer through coupling means including a coupler whose coupling coefficient is in the range of ±30 % of the geometric mean value of the fractional bandwidths of the two filter sections.

Some aspects of band-pass filter design pertaining to amplifier imperfections and mass production†

Abstract: A multiple feedback single amplifier realization of a second order band-pass filter is considered, with certain assumptions made on the amplifier imperfections. The required component values are derived explicitly in terms of the desired filter parameters, the amplifier's open loop finite gain and a degree-of-freedom. The feasible range of the degree-of-freedom is derived. It is then used to either minimize variations of filter parameters due to changes in passive and active components (assuming properties pertaining to hybrid technology components), or minimize the variance of the filter parameters relative variations, in order that all mass produced filter sections of the same type will be similar to each other. For the first case, some useful observations are made concerning the behaviour of the filter under environmental changes, and the allocation of gain to various sections of a cascade filter. Experimental results are reported and compared to anticipated ones.

Performance of a Biphase Bandpass Communication System

Abstract: A binary bandpass communications system is considered, in which the ratio of bandwidth to intermediate frequency (IF) is not necessarily small. Closed-form expressions are given in the case when the receiver (IF) filter has N distinct poles. Explicit results, namely probabilities of error, are computed when the filter is a bandpass Butterworth filter. The effect of k = f_{0}/f_{r} (ratio of half filter bandwidth to IF), f_{0}T (product of half filter bandwidth and bit duration), N , phase and time jitter on probability of error, is investigated.

Purely recursive and non-recursive digital filter - has structure which can be switched over from purely recursive to non-recursive

Abstract: The structure of the digital filter is switched over to give connection in cascade during multiplexing of computers for system parts; it is switched over to the alternative configuration to perform the filter multiplexing for different channels of pulse code modulated transmission systems. The signals being filtered are quantised in time and amplitude. The filter in the pure recursive configuration is used as a low pass filter. In its non recursive form it is used as an echo filter. The filter contains addition, multiplication and division units.

Effect of a high-pass filter on triple correlation measurements

Abstract: An experimental investigation has been made of the effect of a high-pass filter on triple correlation measurements. A random noise signal with a non-symmetrical distribution is generated and passed through a variable high-pass filter. The triple correlation (originally symmetric in time) is measured as a function of cut-off frequency using a modified averaging device. It is found that the high-pass filter introduces a perturbation, anti-symmetric in time, of order ωt / ω0 , where ωt is the filter frequency and ω0 the typical power spectrum frequency. These results agree with an approximate mathematical analysis. It is concluded that the symmetric part of the triple correlation observed in some measurements of fluid turbulence cannot be due to a high-pass filter.

Simple Elliptic-Function Filters Made of Rectangular Waveguide and Semi-Rigid Cables

Abstract: A semi-rigid cable makes a conventional waveguide filter into an elliptic-function filter. A four-resonator elliptic-function filter having a simple construction and a selectivity equivalent to that of a ten-resonator Butterworth filter has been developed by adding a semi-rigid cable to a conventional rectangular waveguide bandpass filter. Although using semi-rigid cable, this filter is equivalent to a rectangular waveguide bandpass filter in unloaded Q. In this filter, two signal portions having passed through different routes offset each other at attenuation poles. Also, a six-resonator filter has been constructed with two semi-rigid cables.

Linear Filter Theory

Abstract: There is frequent need in thermal imaging practice to describe the responses of a system to various signals, to predict spatial resolution, and to devise image enhancement schemes. A tool which is useful for this purpose is linear filter theory1,2, a branch of Fourier transform analysis used for analyzing the signal response of the class of linear, invariant, stable systems. Linear filter theory is applicable to optical, electro-optical, mechanical, and electronic devices. It originated in the description of electrical networks and servomechanisms and was extended to optical systems. Linear filter theory forms an indispensible part of image analysis and is necessary to every thermal imaging system design evaluation.

Delay discriminator for Coran-C radio navigation system - is able to suppress echo and scattering pulses using specified elliptic and two pole filters

Abstract: The delay discriminator, for LORAN-C and other radio navigation systems, discriminates between rapidly following pulses in the same frequency band as well as between pulses in different bands but close together is allows the suppression of echoes and scattering effects. The navigation receiver output is coupled to an elliptic filter (A) whose own output is amplified and passed to a two-pole synchronous filter (B). The latter filter consists of two one-pole filters which are separated by an amplifier. The elliptic filter has a step characteristic centered on the centre frequency whilst the two-pole filter has a continuous curve enclosing the step characteristics of the elliptical filter.

Design of moving-target-indicator filters using a quadrature channel

Abstract: The letter presents a design method for moving-target indicators (m.t.i.) with minimal transient response time. We shall show that the conventional linear-phase real-coefficient digital filter (type A) may be tranformed to an equivalent nonlinear-phase real-coefficient filter (type B), but having half the passband order. Further, the type-B filter can be transformed to obtain a filter of an identical magnitude response, but having half the transient response time (type C).

IF Filter Optimization for CW-FM Radar.

Abstract: : A continuous-wave frequency-modulated radar receiver and the IF filter are described. IF filter responses are investigated from the output of the narrow bandpass filter for various target ranges. The effects of the IF signal pulse width and the duty cycle on the IF filter output including the change of the sidelobe levels out of the filter are examined. Optimum parameters are obtained from the experimental study and from an analytical solution.

Comparison of Finite Zero Butterworth and Chebyshev Filters

Abstract: An accurate expression is derived for the minimum order of a finite-zero Butterworth filter (Dutta Roy 1971) which has a steeper cut-off slope than the corresponding Chebyshev filter (Agarwal et al. 1972). The inaccuracy occurring in the latter is illustrated by a numerical example.