Showing papers on "Butterworth filter published in 1971"

Equal-valued-capacitor active-RC-network realisation of a 3rd-order lowpass Butterworth characteristic

Abstract: The letter describes an active RC network which realises a 3rd-order lowpass Butterworth characteristic. It requires one active element and has the practical advantage that all capacitors have the same value. A design chart is included.

Variable bandpass dynamic noise filter

Abstract: A variable bandpass filter for a dynamic noise filtering effect that reduces the perceptible noise in an audio reproduction system. The variable bandpass filter responds to peak signal levels in relatively high and relatively low frequency portions of the audio spectrum to automatically and independently vary high and low frequency cutoff points for the filter in correspondence with the level of signals at those frequencies. Low distortion and wide dynamic range is achieved in a filter configuration which comprises a forward signal path and a reverse signal path, each having a variable integration response provided by temperature compensated and linearized field-effect transistor circuits. The integration response of the two paths imparts a high and low frequency filtering effect. A further constant gain feedback path establishes a uniform middle frequency amplification for the variable bandpass filter.

Transitional Butterworth-Chebyshev filters

Abstract: A function is presented which has properties that lie between those of the Butterworth and Chebyshev functions.

On maximally flat sharp cutoff low-pass filters

Abstract: Maximally flat (MF) low-pass filters with multiple pairs of coincident or distinct imaginary axis zeros are investigated and compared with the all pole Butterworth filters. It is shown that for the same order n , finite zero filters provide much sharper cutoff than Butterworth filters, and that the cutoff slope increases with increasing number of zeros. Expressions for cutoff slope and minimum attenuation in the stopband are derived in terms of n , the number of pairs of zeros ( m ) and their locations. In the case of coincident multiple zeros, the stopband performance is found to be an optimum for a particular value of m . The information required for design of finite zero filters is provided in the form of universal graphs and use of these graphs is illustrated by a design example.

Electrical filter circuit

Abstract: The present electrical filter circuit has a plurality of filter paths connected in parallel to each other between an input and an output. At the input side of each path there is arranged a bandpass filter which is then followed by logic circuit and bypass means interconnected in such a manner that only one path at a time is closed to the exclusion of all other paths in response to the signal level at the output of the respective bandpass filter means.

Distortion Analysis of Binary FSK

Abstract: The performance of the binary frequency-shift keying (FSK) data system employing a conventional limiterdiscriminator detector is analyzed. Both additive noise and distortion produced by the transmitter and receiver bandpass filters are taken into account. Performance tradeoffs with respect to transmitter frequency deviation, bandpass filter shape, and bandpass filter bandwidth are investigated. Intersymbol interference caused by distortion is taken into account for each bit sequence by calculating two distortion factors. The first factor is related to the actual baseband signal distortion produced by the bandpass filters. The second factor is related to the power distortion caused by the bandpass filters. It is shown that both factors must be considered in determining the detrimental effect of distortion on system error probability. Three particular bandpass filter shapes are considered. They are the first-, second-, and third-order Butterworth filters. For each of these filter shapes the binary FSK data system is optimized over transmitter frequency deviation and bandpass filter bandwidth. It is found that the third-order Butterworth filter operating at a 3-dB bandwidth of 1.1/T Hz, where T is the bit interval, coupled with a transmitter frequency deviation of 0.36/T Hz yields the best performance for the binary FSK system with limiterdiscriminator detection. This bandwidth (64 percent of the Carson's rule bandwidth) optimizes a tradeoff between additive noise and distortion effects. This frequency deviation optimizes a tradeoff between the spike and nonspike noise components of the discriminator output. It is shown that the performance of the optimized binary FSKlimiter-discriminator system closely approaches the performance obtained by using an optimum coherent detector on the FSK signal set.

Band pass filter with transmission line section

Abstract: A filter circuit formed of inductive and capacitive elements and arranged to pass a predetermined band of frequencies A transmission line section having a length equal to one-fourth of the wave length of a predetermined frequency above the pass band is connected either at the filter input, the filter output, or at each end of the filter to provide high attenuation at the predetermined frequency

Estimating frequency-response function using periodic signals and the f.f.t.

Abstract: A technique for estimating a frequency-response function using a periodic pseudorandom binary sequence which is compatible with the fast-Fourier-transform algorithm is presented. A method of synchronising the p.r.b.s. and the sampling for the f.f.t. using a single clock source and two binary counters is described. A simple check on the synchronisations and the identification of an 8th-order lowpass Butterworth filter is provided.

Highly selective filter circuit

Abstract: A filter circuit providing extremely sharp attenuation at a selected frequency cutoff point. The sharp attenuation is obtained through the use of several ganged or cascaded active filter sections whose characteristics are combined in an additive fashion to provide an extremely flat passband characteristic and a sharp attenuation curve at the desired frequency cutoff value. Filter circuits of this design may be used in combination in the electrocardiograph field to isolate the R-wave of the PQRS complex of an electrocardiogram resulting in trigger signals of a high degree of accuracy for purposes of R-wave detection and evaluation.

Method of designing orthogonal filters

Abstract: A method of designing an orthogonal filter for use in a speech synthesizing system wherein the filter is constructed from a series of linear filter sections. The poles in the complex plane of any section of the filter are cancelled by the zeros of the next section.

Radio-frequency band-pass filter wherein magic-tee arms are coupled to cavities and resonators

Abstract: A radiofrequency band-pass filter having a flat amplitude response and a substantially constant group delay characteristic in the passband, these being obtained by the integrated combination of a magic-tee terminated with reflecting cavities, and input and output transmission resonators, the integration of the components being essential to achievement of the above characteristics. For the same complexity this filter has a higher stop-band attenuation and smaller midband insertion loss than a conventional nonintegrated filter/phase-equalizer combination.

Extraction of signals from noise through Wiener filtering

Abstract: This paper deals with the problem of finding a Wiener filter when the length of the filter output in not larger than the length of the filter input. Measure for the efficiency of a filter is defined in terms of the relation between the desired filter output and the actual filter output. This measure, called the filter efficiency, is used to find the optimum length of the filter memory function. The relation between the signal-to-noise-ratio (SNR) of the filter input and the SNR of the filter output is discussed. It is shown that there is always some improvement in the SNR through the use of a Wiener filter.

Filter and substitute for resonant reed relay

Abstract: A monostable multivibrator is connected to a differential amplifier to perform the following functions: signal limiter, band-pass filter, low-pass filter, high-pass filter and frequency modulation detector.

An analysis of frequency distortion in digital filter design.

Abstract: The theory and background of the algebraic substitution synthesis method for the digital filters from continuous filter characterizations is presented with emphasis on the frequency distortion phenomenon. An analysis of the Forward Euler, Backward Euler and Trapezoidal numerical integration algorithms is undertaken and appropriate transformations are obtained. A general integration formula, encompassing the above algorithms as special cases, is analyzed and its application to the synthesis problem is pointed out. Direct transformations for discrete filter frequency response characteristics from continuous filter characterizations are derived. TABLE OF CONTENTS