Showing papers on "Butterworth filter published in 1979"

Loss sensitivities in singly and doubly terminated filters

Abstract: The loss of a conventional doubly terminated filter is far less sensitive than the loss of a singly terminated filter to errors in the component values. This property, first pointed out in 1966, has motivated many new high quality RC-active and digital filter design techniques. It is not so widely appreciated, however, that this superiority of the doubly terminated filter also holds for errors in the terminating resistances as well as for errors in the components inside the filter. The nature of these sensitivities in both types of filter is discussed in some detail, and Illustrated by means of a numerical example.

Band-pass filter circuit

Abstract: A band-pass filter circuit comprising a band-pass filter for removing noise modulation components from an input signal comprising a carrier sine wave, a phase detector for detecting a phase difference between input and output signals of the band-pass filter, a loop filter supplied with the output from the phase detector, and automatic control means for effecting control by the output from the loop filter so that a difference between the frequency of the input sine wave and the center frequency of the band-pass filter is reduced to zero. For carrier recovery in a burst mode, the loop filter is selected for each particular case so that high-speed pulling-in is possible even if a narrow-band filter is employed as the band-pass filter for the removal of noise components. Also, high-speed and high-precision pulling-in is achieved when many bursts of different frequencies are applied in one frame period. Further, when common and individual frequency variations occur at the same time, high-speed pulling-in is also achieved for each burst.

Tracking filter for FM threshold extension

Abstract: A tracking filter suitable for use in the IF stage of FM receiver circuitry incorporates a bandpass filter the components of which yield a characteristic that permits the filter to provide substantially the entirety of a required 90° phase shift for phase detection control circuitry that rapidly actively tunes capacitive components of the filter without imparting unacceptable group delay behavior to the configuration. The filter is a two-pole pair, single zero at the orgin, bandpass filter inserted in the signal path between a pair of signal power splitters. Part of the input signal is applied from the first splitter to one input of a phase comparator the other input of which is derived from the output signal via the second power splitter. The output of the phase comparator is applied through a broadband control amplifier to actively adjust the center frequency of the bandpass filter. Advantageously, this configuration enables the filter to have its center frequency effectively coincide with the instantaneous frequency of the deviating input signal, whereby an increase in performance over conventional filter approaches is obtained.

CMOS switched-capacitor filter for a two-chip PCM voice coder

Abstract: This paper will cover a CMOS switched-capacitor filter for a PCM CODEC Circuit consists of an elliptic low-pass ladder, a biquadratic high-pass filter and a state-space elliptic low-pass filter with a built-in sin X/X corrector

Explicit design formulae for digital tan filters with low-pass, high-pass, band-pass, and band- stop characteristics

Abstract: Explicit expressions of transfer functions for digital tan filters with low-pass, high-pass, band-pass, and band-stop characteristics approximating given design specifications are advanced. The higher order transfer function satisfying the design specification is expressed as the product of first-order and second-order filter sections of identical forms but with different coefficient values. All coefficients of these low-order filter sections are expressed in explicit forms related simply to the specification values. Thus, the result developed can be easily applied for the cascade or time-sharing realization. The low-order filter section developed here can be implemented with the fewest multipliers. The design formulae for Butterworth, Chebyshev, inverse Chebyshev and elliptic approximations are included. The transfer functions for all these filters are expressed in the same form of low-order filter section with different coefficient values.

A comparison of different window formulations for two-dimensional FIR filter design

Abstract: Two-dimensional windows are generally derived by beginning with a one-dimensional window as a prototype and either rotating that window in the 2-D plane to produce a window with a round region of support or forming the outer product of that window with itself to produce a window with a square region of support. In this paper we present a comparison of results obtained using these two window formulations for 2-D FIR filter design. Design formulas are produced for estimating filter order for a given set of frequency domain specifications when a one-dimensional Kaiser window is used as the prototype window. The results suggest some interesting differences from the one-dimensional case.

Bandpass filter circuit

Abstract: An improved bandpass filter circuit for selecting a relatively narrow band portion of an input sinusoidal signal. The improved bandpass filter circuit produces an output signal whose phase deviation from the input signal is substantially constant for small variations in the frequency of the input signal. The improved bandpass filter circuit in accordance with the present invention does not use feedback control in its operation and therefore is free from the inherent delay time of a tracking type bandpass filter utilizing feedback control in handling transitory input signals.

Equivalent Statistical Bandwidths of Conventional Low-Pass Filters

Abstract: The equivalent statistical bandwidths of low-pass Butterworth filters up to ten poles and Chebyshev filters up to eight poles for six different passband ripple levels have been computed and are tabulated along with the corresponding noise bandwidths. The results should be useful for evaluating the statistical error arising from power spectrum measurements such as encountered in the sensitivity analysis of microwave radiometer systems.

Adjustable passband filter

Abstract: An adjustable passband filter comprises at least one reentrant section in shunt with a transmission line, which section can be electronically switched between different conditions. The reentrant section, when in at least one condition acts, to reduce the band of frequencies passed by the transmission line by increasing the effective capacitance of the filter and when in another condition, operates as an open circuit, whereby the filter exhibits a broader passband.

Active high-power bandpass filter

Abstract: An active power-line filter which provides bandpass filtering and transientuppression. The high-power signal to be filtered is modulated to form a chopped waveform within an envelope defined by the input waveform and the modulation is removed by passing the chopped signal through a low-pass filter. The output of the low-pass filter is then compared in a differential amplifier with a low-power reference signal which is phase-locked to the primary component of the high-power signal. The output of the differential amplifier is phase-compensated for the effects of the low-pass filter and is compared to the reference in a phase-detection multiplier to produce an error signal to adjust the duty cycle of the chopped waveform so that the waveform at the output of the low-pass filter is identical to the reference waveform. For periods when the high-power signal is out of phase with its primary component, the polarity of the high-powered signal is reversed at the input of the active filter to allow the filter to compensate for this situation.

High pass filter and method of making same

Abstract: There is provided a high pass switched capacitor filter having low bandpass ripple. The present filter does not have peaking near its center frequency when sampled at switching frequencies used in communication systems. The high pass filter has three switched capacitor integrators providing a 3-pole Chebyshev high pass switched capacitor filter. A fourth switched capacitor integrator is used to provide an output for the filter. A method of implementing the high pass filter from a set of parameter requirements is also provided. The capacitors used in this filter are ratios of each other and the filter readily lends itself to being implemented as a monolithic integrated circuit, particularly as a CMOS circuit.

Active filter for providing improved notch and band pass filters

Abstract: An active filter is disclosed for providing improved notch and band pass filters. The output to input frequency response of an active filter is mathematically expressed as a ratio of two polynominals in the Laplace operator S. In any notch filter, the coefficient of the S term in the numerator must be reduced to zero, while in any band pass arrangement the coefficient of the S term in the denominator is reduced to zero. The improved notch filter provides an input circuit for the operational amplifier portion of the filter which eliminates the S term in the numerator so that adjustments to reduce this term are unnecessary. Similarly, in the improved band pass filter, the S term in the denominator is eliminated in the feedback circuit provided for the operational amplifier, so that adjustment is unnecessary to eliminate the coefficient of S.

SAW Butterworth Contiguous Filters at UHF

Abstract: Abstruct-The design, fabrication, and testing of a set of 16 dualchannel contiguous surface acoustic wave (SAW) Butterworth filters is described. Each filter has a narrow-band (10.15 MHz) and wide-band (20.3 MHz) channel, and center frequencies vary from 248.8 MHz to 401.2 MHz. Theory for determination of finger overlap functions yielding Butterworth frequency responses is given. The SAW substrate used is the minimal diffraction cut of LiTa03 which has excellent bandpass filter properties. In addition to having diffraction suppressed by a factor of 20 over isotropic materials, these properties include superior spurious mode rejection when compared to other popular SAW substrates, and a coupling constant or kZ of 0.0154. An accurate transducer circuit model including parasitic elements is determined to allow optimum choice of matching elements for addressing insertion loss, VSWR, and triple transit suppression design goals. Direct optical projection onto the SAW substrate from 1OX negative masters in combination with the photoresist stripping technique was used for fabrication. Agreement between theory and experiment is good and double detection frequency measurement using SAW Butterworth filters is demonstrated.

Eigenvalues of a matrix inside an ellipse and Chebyshev filter

Abstract: The conditions for a matrix to have all its eigenvalues inside an ellipse are obtained and explained in terms of a vector norm. A set of functions orthogonal on the ellipse is obtained and the relation between the Chebyshev filter and these functions is presented. The Butterworth filter is derived as a particular case.

Commutating narrowband filter

Abstract: A signal to be filtered is applied to a commutating filter which is contred by a tunable oscillator tuned to a desired filter frequency. The commutating filter includes a plurality of RC networks to which the input signal is sequentially connected. The output of the commutating filter is a series of discrete voltages from the capacitor sections and of the RC networks which are fed to an analog to digital converter. The resulting digital words produced by the converter are stored in a microprocessor and used to compute the spectral content of the input signal by means of the Discrete Fourier Transform. The computed output from the microprocessor represents the effect of the cascaded filter sections of the system.

Minimal distortion video bandpass filter

Abstract: The present video bandpass filter passes a sinusoidal video output in response to a square pulse input. The video band-pass filter rejects d.c. and low frequency signal components as well as noise and spurious signals generated at the transmitting source. The video bandpass filter is comprised of an M-derived filter, a series-tuned notch filter, and a final d.c. blocking series-tuned filter which, together, pass the desired video with minimal distortion.

A 128-kHz mechanical channel filter with finite-frequency attenuation poles

Abstract: The paper describes the design and manufacture of a miniaturized 128-kHz pole-type mechanical channel filter for FDM communication systems. By introducing a new phase inversion structure to realize the finite attenuation poles, and by minimizing sensitivity in the circuit design, we have designed and manufactured a miniaturized high-performance mechanical channel filter. The filter volume is 10.7 cm3, which is about ⅙ that of conventional LC channel filters. The passband response satisfies the 1/20 CCITT Recommendation. With this filter, we have developed a channel modem compact enough to mount 900 channel units per standard bay. Manufacturing steps and material characteristics are described in some detail. We also briefly discuss some future considerations in further miniaturizing the channel filter.

Self-adjusting bell filter circuit for use in SECAM coders

Abstract: A method and circuit for adjusting the frequency response of a bell filter in a SECAM camera samples the output signal from the filter. A frequency control voltage is applied to the filter in accordance with the sampled voltage.

Switched capaciter filter and method of making same

Abstract: There ist provided a high pass switched capacitor filter having low bandpass ripple The present filter does not have peaking near its center frequency when sampled at switching frequencies used in communication systems The high pass filter has three switched capacitor integrators (10, 25, 40) providing a 3-pole Chebyshev high pass switched capacitor filter A fourth switched capacitor integrator (50) is used to provide an output for the filter A method of implementing the high pass filter from a set of parameter requirements is also provided The capacitors used in this filter are rations of each other and the filter readily lends itself to being implemented as a monolithic integrated circuit, paricularly as a CMOS circuit

Filter for separation of two frequency spectra - has resistances of RC filter sections switched between two values at high frequency

Abstract: The spectra are found in the output signal of a measurement sensor of a surface testing instrument. The filter comprises at least one RC section with adjustable pass-band. The resistance of the RC filters (8, 9, 18, 36) can be switched between two values at a frequency higher than the frequency to be separated. Switching-on times of the two resistances, determining the filter (8, 9, 18, 36) cutt-off frequency are adjustable.

A maximally flat filter design algorithm for quadrature mirror filters (QMF)

Abstract: This paper describes a numerical procedure for designing maximally flat quadrature mirror filters (QMF) for use in split-band voice coding systems. As originally proposed by Croisier, et al, the FIR filters used in QMF structures must possess certain characteristics in order to achieve perfect reconstruction of a decomposed signal (1). These constraints require that the elementary filter response exhibit an odd symmetric property about the quarter-band frequency and the 3 dB point. In addition, the filter must exhibit highly attenuated stop bands in order to orthogonalize the adjacent subbands. A filter design algorithm proposed by Herrman has been implemented and structured to satisfy these QMF constraints (2). A detailed analysis of this maximally flat FIR approach to QMF design will be discussed along with the problems associated with its implementation.

Noise cancellation and inverse filtering using a compact high-performance c.c.d. adaptive filter

Abstract: This letter describes results obtained from a compact adaptive filter based on a charge-coupled device, programmable, analogue transversal filter. The adaptive algorithm used was the Widrow l.m.s. algorithm and results are presented for the 64-filter-point system used as a self-tuning filter, a noise canceller and as an inverse filter. The results illustrate the high quality of performance possible using this structure.

Alternative approach to the design of switched-capacitor filters

Abstract: An alternative switched-capacitor filter design is shown to be possible using an economic form of c.c.d. A simple example of a biquadratic digital-filter section is included to illustrate the point. This leads to comment on the relationship between switched-capacitor filters, the N-path filter and the digital filter.

A design technique for transitional butterworth-Chebyshev filters

Abstract: For most of the given filter orders, the design technique reported recently [1] can generate neither a complete nor a gradual transition of filters between the Chebyshev and Butterworth extremes. An alternative design is proposed here without such difficulties.

A method for the design of phase equalizers

Abstract: A new method for the design of all-pass filters with arbitrary group delay characteristics is presented. Given the desired group delay, the magnitude of the corresponding minimum phase filter is found. The problem is then reduced to that of approximating a magnitude response by a stable all-pole filter or by a Finite-duration Impulse Response (FIR) filter with all its zeros outside the unit circle. It is shown with several examples that the resulting errors can present an almost equal ripple behavior. Comparisons with optimum L p designs are made.

Filter for converting pulse width modulation to amplitude modulation

Abstract: In a high efficiency amplitude modulation circuit. A pulse width modulation switch is arranged with a low pass filter to attentuate switching frequencies of the switch. A diode is connected in parallel with the input terminals of the low pass filter which diode provides a current discharge path for the filter while the switch is non-conductive. A further filter is also connected in parallel with the input terminals of the low pass filter, this further filter being arranged to provide cancellation of the input susceptance of the low pass filter over at least part of its pass band. The two filters in combination are such as to present a constant input conductance over at least part of the pass band of the low pass filter.

A maximally flat group delay recursive digital filter with improved passband magnitude response

Abstract: A technique is proposed for the design of a recursive digital filter with maximally flat responses in both magnitude and group delay. In comparison to the previous designs [1]-[3], the magnitude and group delay always show smooth responses no matter what the difference is in the polynomial degrees of the numerator and denominator.

Comments on "Lower Bounds on the Summed Absolute and Squared Voltage Transfer Sensitivities in RLC Networks

Abstract: Weyten's observation based on the worst case sensitivity study of a third-order Butterworth low-pass (LP) filter is questioned. For most practical purposes, the doubly terminated lossless ladder is less sensitive than the singly terminated lossless ladder.