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Showing papers on "Band-stop filter published in 1978"


Patent
30 May 1978
TL;DR: In this article, a tracking band-pass filter was proposed for locking onto, and passing, an input signal which changes rapidly in frequency, using a frequency pass band controlled by a rectangular voltage waveform derived from the output signal passed by the filter.
Abstract: A tracking band-pass filter useful for locking onto, and passing, an input signal which changes rapidly in frequency. The filter has a frequency pass band controlled by a rectangular voltage waveform which is derived from the output signal passed by the filter. The filter output signal is translated from a sine wave to a pulse wave. The period between each two successive pulses is measured by counting the cycles of an oscillator during each respective period. The time-representing count is inverted to a frequency-representing count which controls the duty cycle of a rectangular wave used to make the filter track the changing frequency of the input signal.

91 citations


PatentDOI
TL;DR: In this article, a moving-average notch filter with a well-defined phase characteristic was proposed for eliminating oscillation frequencies in a sound amplification system, wherein this moving average filter was designed to have an output Y K in accordance with the system equation where b 1 are the weighting coefficients, X K-i are input samples, and K is a constant.
Abstract: A moving-average notch filter with a well-defined phase characteristic for use in eliminating oscillation frequencies in a sound amplification system, wherein this moving-average filter is designed to have an output Y K in accordance with the system equation ##EQU1## where b 1 are the weighting coefficients, X K-i are input samples, and K is a constant. This filter may be designed to have a linear phase characteristic. In one embodiment, the location of the notch in the frequency response of the filter may be made to automatically track the drift of an acoustic oscillation frequency.

39 citations


Patent
18 Jul 1978
TL;DR: In this article, an adaptive filter network comprising a controllable filter having an adjustable cut-off frequency and adapted for varying the pass-band of the network is presented, which includes a serial arrangement of an algebraic adder for generating control signals, connected to the controLLable filter; a weighting filter for converting the control signal spectrum in response to the load sensitivity variation with frequency; a threshold limiter for setting the noise reduction threshold level of the adaptive filter networks; a control signal frequency corrector; and an amplitude detector for shaping control signals applied to the control input
Abstract: An adaptive filter network comprising a controllable filter having an adjustable cut-off frequency and adapted for varying the pass-band of the network. The adaptive filter network further includes a serial arrangement of an algebraic adder for generating control signals, connected to the controllable filter; a weighting filter for converting the control signal spectrum in response to the load sensitivity variation with frequency; a threshold limiter for setting the noise reduction threshold level of the adaptive filter network; a control signal frequency corrector; and an amplitude detector for shaping control signals applied to the control input of the controllable filter. The network analysis of the input audio signal spectrum and the width of its pass-band is varied depending on the present frequency limit of the input audio signal wanted components.

20 citations


Patent
Enn Vali1
08 Jun 1978
TL;DR: In this article, a flexible notch filter for use in a servo system to eliminate natural mechanical resonance was proposed, where the in-phase output of the filter is fed back into the filter.
Abstract: This invention relates to a flexible notch filter for use in a servo system to eliminate natural mechanical resonance. The filter is an improved "twin-T" type where the "in-phase" output of the filter is fed back into the filter. Varying the feedback varies the bandwidth of the filter. The improved filter further provides for attenuation control in addition to control of the center frequency of the filter. The advantage of this filter over prior art designs is that one filter may be manufactured and adapted to be used in many servo systems since the filter can be easily adjusted to effectively eliminate the natural resonating frequency of the machine in addition to reducing phase lag at frequencies below the center frequency of the notch filter.

19 citations


Patent
05 Sep 1978
TL;DR: In this article, a citizens band transmitter employing negative overall envelope feedback in the final RF stage obtains the feedback signal from a filter in the antenna coupling network which has a phase shift of 90 degrees or an odd multiple thereof at the radio frequency.
Abstract: A citizens band transmitter employing negative overall envelope feedback in the final RF stage obtains the feedback signal from a filter in the antenna coupling network which has a phase shift of 90 degrees or an odd multiple thereof at the radio frequency. A pair of detector diodes have their cathodes connected to opposite ends of filter and their anodes connected to a low pass filter to provide an envelope of the higher of the two voltages at either end of the filter in the coupling circuit in negative feedback to the modulating signal.

14 citations


Patent
29 Sep 1978
TL;DR: In this article, an active filter which can achieve extremely high attenuation of frequencies outside the passband while maintaining a very low phase shift of signals within the pass band is described.
Abstract: An active filter which can achieve extremely high attenuation of frequencies outside the passband while maintaining a very low phase shift of signals within the passband. A preferred embodiment is described in which two, second-order, multiple-feedback, active filter circuits are cascaded and the output of the second filter is fedback to the input of the first filter to realize a fourth-order filter which has very high attenuation of signals falling outside the passband while providing very low phase shifts of signals within the passband.

13 citations


Patent
20 Oct 1978
TL;DR: In this paper, a cavity notch filter for series connection in a transmission line is disclosed which comprises a high Q cavity (2) containing an inductively coupled L-C series circuit (19).
Abstract: A cavity notch filter (1) for series connection in a transmission line is disclosed which comprises a high Q cavity (2) containing therein an inductively coupled L-C series circuit (19). The notch filter (1) acts as a high series impedance at the resonant frequency of the cavity. At frequencies off resonance, the filter is characterized by low impedance so as to produce broad lateral pass bands. A multicoupler (18) for connection of a plurality of signaling devices (15) to a single antenna (16) may be assembled to comprise two or more of the filters (1) inserted into the transmission line (17); each being tuned to resonate so as to produce a notch at the respective frequency of the signaling device (15). A different signaling device (15) is connected to each of the series connected notch filters (1) at a junction (7). Energy at all frequencies is then permitted to propagate down the line except the energy at the frequency of the respective signaling device (15). This frequency is blocked by the series notch filter (1) at the junction (7) and is diverted to the respective signaling devices (15).

10 citations



Journal ArticleDOI
TL;DR: In this article, the stationary Kalman filter is approximated by a notch filter together with a low-pass filter in cascade in order to remove unwanted wave motion signals in dynamic ship positioning systems.
Abstract: In dynamic ship positioning systems notch filters have been used mainly to remove the unwanted wave motion signals. Recently, Kalman filters have been introduced for this purpose. It is demonstrated that for this application the stationary Kalman filter is approximated by a notch filter together with a low-pass filter in cascade.

9 citations


Patent
06 Sep 1978
TL;DR: In this article, a frequency band dividing filter comprises a delay-line filter, which is supplied with an input signal and produces a divided frequency band signal as an output, a circuit for deriving a delayed signal in which the input signal has been delayed by a predetermined amount of time, and an adder for adding output signals of each of the coefficient multipliers.
Abstract: A frequency band dividing filter comprises a delay-line filter which is supplied with an input signal and produces a divided frequency band signal as an output, a circuit for deriving a delayed signal in which the input signal has been delayed by a predetermined amount of time, and a circuit for substantially performing subtraction of the delayed signal output signal of the delay-line filter, and producing another divided frequency band output signal. The delay-line filter comprises a plurality of delay circuits cascade connected, coefficient multipliers respectively supplied with the input signal and the output signal of the delay circuits and for multiplying specific coefficients to the signals thus supplied, and an adder for adding output signals of each of the coefficient multipliers.

8 citations


Patent
27 Nov 1978
TL;DR: In this article, temperature sensors are used to excite resonance tubes whose frequency response is a function of temperature, whose outputs of these sensors control a fluidic amplifier whose output is rectified and filtered to produce a D.C. fluid signal, which is then used to sense the difference between two temperatures.
Abstract: The temperature sensors shown utilize a constant frequency fluidic oscillr to excite resonance tubes, whose frequency response is a function of temperature. The outputs of these sensors control a fluidic amplifier, whose output is rectified and filtered to produce a D.C. fluid signal which is a function of the sensed temperature. Different embodiments utilize resonance tubes excited in phase or 180° out of phase to sense the difference between two temperatures or to provide increased sensitivity.

Patent
01 Nov 1978
TL;DR: In this article, a two-stage transmission notch filter was achieved with one stage of microwave circuitry by reflecting the microwave power back through a single stage device, and the phase shifter was inserted into one delay line for tuning and a non-reciprocal phase element was used to prevent reflected signals from emerging from the input port.
Abstract: A two stage transmission notch filter characteristic is achieved with one stage of microwave circuitry. Elimination of the second stage is accomplished by reflecting the microwave power back through a single stage device. Structurally, the adjacent ports of two 3 dB directional couplers are directly connected by delay lines of unequal delay times. The opposite adjacent ports of one coupler comprise the device input and output while the opposite adjacent ports of the other coupler are terminated in a manner that reflects microwave power back through the device. A phase shifter is inserted into one delay line for tuning and a non-reciprocal phase element is used to prevent reflected signals from emerging from the input port.

Patent
01 Nov 1978
TL;DR: In this paper, a magnetic bubble memory detector-amplifier for use with a bubble memory device having the dual output from an active and a dummy bubble detector in combination consists of a differential amplifier associated with constant current sources to drive the bubble detector elements, a notch filter coupled to the output of the differential amplifier to eliminate the rotating magnetic field frequency component, and, finally, a self-biasing detector coupled with a strobed output flip-flop.
Abstract: A magnetic bubble memory detector-amplifier for use with a bubble memory device having the dual output from an active and a dummy bubble detector in combination consists of a differential amplifier associated with constant current sources to drive the bubble detector elements, a notch filter coupled to the output of the differential amplifier to eliminate the rotating magnetic field frequency component, an amplifier coupled to the output of the filter which is controlled by a bias pulse at the fundamental frequency of operation to provide a reference for better discrimination between "ones" and "zeros," and, finally, a self-biasing detector coupled with a strobed output flip-flop.

Journal ArticleDOI
TL;DR: A new active R filter which realizes a second order bandpass transfer function is given and its design equations are given and experimental results are also included.
Abstract: A new active R filter which realizes a second order bandpass transfer function is given. The network employs only resistors and two operational amplifiers. Sensitivities to all passive and active circuit components are very low. Design equations are given and experimental results are also included.

Patent
25 Apr 1978
TL;DR: In this article, the group delay characteristics of band limiting filter 2 and interpolating filter 7 are made complementary each other, which makes it possible to reduce the generation of transmission waveform distortion even when both A/D conversion and D/A conversion are repeated several times.
Abstract: PURPOSE: To make it possible to reduce the generation of transmission waveform distortion even when both A/D conversion and D/A conversion are repeated several times in a signal processing system composed of an analog unit, a digital unit, a band-limiting filter and an interpolating filter. CONSTITUTION: After being band-limited by band-limiting filter 2, input video signal 1 is converted by sample holder 3 and A/D converter 4 into a digital signal, which is processed by digital signal processing part 5 and then recoverted into the analog signal by D/A converter 6 to obtain output video signal 8 through interpolating filter 7. Then, group delay characteristics of band limiting filter 2 and interpolating filter 7 are made complementary each other. COPYRIGHT: (C)1979,JPO&Japio

PatentDOI
TL;DR: In this article, a special effects circuit for use in an electronic musical instrument, preferably an electronic organ, including a filter circuit having variable bandpass characteristics and a tone source supplying a signal to the input of the filter circuit.
Abstract: A special effects circuit for use in an electronic musical instrument, preferably an electronic organ, including a filter circuit having variable bandpass characteristics and a tone source supplying a signal to the input of the filter circuit. The bandpass characteristics of the filter circuit are modified in accordance with a control signal. Upon the occurrence of an input signal, a control circuit provides the filter circuit with the control signal at a random or pseudo-random value. The instrument player may select the source of input signals from a variety of sources within the organ thereby determining the times or frequency at which the control signal changes but the value of the control signal is random or pseudo-random. The tone signal output from the filter circuit has randomly or pseudo-randomly attenuated frequency characteristics and is coupled to standard organ output circuits for audio presentation.

Proceedings ArticleDOI
01 Apr 1978
TL;DR: This paper discusses the use of a recursive nonlinear filter that is recursive, and synthesized in one of the two alternative structures, both the memory and computation requirements are low enough to permit efficient on-line implementation.
Abstract: The ill-posed nature of direct deconvolution has prevented its use in applications such as channel equalization or inversion of transducer distortion. In this paper we discuss the use of a recursive nonlinear filter. The design of the proposed filter is accomplished in two stages. First, a constrained least-squares technique is employed to obtain, off-line, a filtered signal from a typical distorted signal. Then this pair of signals is used in a model identification scheme, to arrive at the nonlinear recursive filter. Since the final filter is recursive, and synthesized in one of the two alternative structures, both the memory and computation requirements are low enough to permit efficient on-line implementation.

Proceedings ArticleDOI
01 Sep 1978
TL;DR: In this article, a theory for the design of coupled-line bandpass filters has been derived, which includes the possibility of altering the band-pass center frequency for a given length of the resonators.
Abstract: A theory for the design of coupled-line bandpass filters has been derived. The filter comprises cascaded sections of two-port stepped coupled-line sections of length ?/4 and with individual wave impedance parameters within each ?/8 section. The design includes the possibility of altering the band-pass center frequency for a given length of the resonators. Narrow-band maximally flat or equal-ripple filter can be designed. The flexibility in filter length can be exploited for reducing space at low frequencies or for increasing the transmission line length-width ratio at high frequencies where the effect of end capacitance can be troublesome.

Journal ArticleDOI
TL;DR: Multirate discrete ladder filter structures are proposed that, when implemented as a digital filter, achieve better passband accuracy than the corresponding uniform-rate filter and may be implemented without the use of digital multipliers and consequently with simpler hardware and reduced filter processing times.
Abstract: Multirate discrete ladder filter structures are proposed that, when implemented as a digital filter, achieve better passband accuracy than the corresponding uniform-rate filter and, of more importance, may be implemented without the use of digital multipliers and consequently with simpler hardware and reduced filter processing times.

Proceedings ArticleDOI
27 Jun 1978
TL;DR: In this article, an improved waveguide bandstop filter configuration with two realizable design examples is presented with the same dielectric resonators used in the original waveguide filter configuration.
Abstract: Waveguide bandstop filter structures utilizing dielectric resonators proposed in the literature have problems in realization. An improved filter configuration is presented with two realizable design examples.

Proceedings ArticleDOI
10 Apr 1978
TL;DR: An algorithm is presented for designing multi-band FIR digital filters to suppress wideband or bimodal clutter in MTI radars in which the passband edges are varied to maximize the usable bandwidth over which a signal is detected with acceptable probability while maintaining specified clutter rejection.
Abstract: An algorithm is presented for designing multi-band FIR digital filters to suppress wideband or bimodal clutter in MTI radars. The technique is an iterative process in which the passband edges are varied to maximize the usable bandwidth over which a signal is detected with acceptable probability while maintaining specified clutter rejection. The clutter-bandwidth tradeoff is shown to be a function of such interrelated filter parameters as number of taps, transition widths, passband ripple, variable stopband attenuation, and stopband width. A 25-tap bandstop filter design is presented which provides 70% usable bandwidth while maintaining 20 dB wideband clutter rejection. The design is then modified to include an additional 50 dB ground clutter attenuation. The resulting 26-tap multi-band filter meets all specifications while still retaining 60% usable bandwidth. An alternative technique for bimodal clutter rejection is presented which utilizes the natural null at dc for an N-even bandstop filter to attenuate the ground component.

Patent
16 Jun 1978
TL;DR: In this article, a trap filter is provided between the antenna and the FM multiplexer for arresting the 19 KHz stereo pilot signals, while the signals derived from the low-pass filter are introduced into the above mentioned circuit path.
Abstract: Information signals, 19 KHz stereo pilot signals and interference signals are received at an antenna and then applied to a low-pass filter and a high-pass filter. The interference signals derived from the high-pass filter control a gate which is disposed in a circuit path including the low-pass filter, a subcarrier generator and an FM multiplexer for the interference reduction purposes. A trap filter is provided between the antenna and the FM multiplexer for arresting the 19 KHz stereo pilot signals, while the signals derived from the low-pass filter are introduced into the above mentioned circuit path.

Proceedings ArticleDOI
01 Oct 1978
TL;DR: In this article, a generalized fin-line structure is analyzed, which shows several slots in the metal coating of the substrate, and possible applications of such a structure are e.g. directional couplers and 3 dB hybrids.
Abstract: A generalized fin-line structure is analyzed, which shows several slots in the metal coating of the substrate. Possible applications of such a structure are e.g. directional couplers and 3 dB hybrids. Out-off frequencies, phase constants, and electric and magnetic field patterns are calculated by a numerical approximation method. Results are presented for the specialized cases of isolated and earthed finlines both with one and two slots of varying width. As an application, the calculated and measured performance of a bandstop filter is given.

Proceedings ArticleDOI
10 Apr 1978
TL;DR: A filter structure based on digital incremental computers is proposed, which has low sensitivity and roundoff errors, and simple hardware implementation, and can be directly used on differentially pulse-code modulated signals.
Abstract: Narrow band digital notch filters have their poles near the unit circle. As the sampling rate is increased, the poles move towards z = +1. Implementing such filters requires long registers to overcome the sensitivity and roundoff errors. A filter structure based on digital incremental computers is proposed, which has low sensitivity and roundoff errors, and simple hardware implementation. The filter structure can be directly used on differentially pulse-code modulated signals. Hard-ware multipliers are not required as the poles approach z = +1, and excellent results can be obtained using multipliers with very short word lengths, or with small size read-only memories.

Journal ArticleDOI
TL;DR: In this article, a rational, two-port model for uniformly distributed-RC (URC) notch filters is presented, in the idealized case of absence of parasitics, the model accurately predicts the actual characteristics over a wide frequency range.

Patent
13 Sep 1978
TL;DR: In this article, a distortion measurement system for measuring distortion as low as 0.002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling.
Abstract: A distortion measurement system for measuring distortion as low as 0.002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling. The analyzer section included in the distortion system has a unique notch filter which provides low distortion. This is achieved by adding together two 90 DEG all pass phase shifters. In addition, automatic tuning is provided by two feedback control loops; one is responsive to out-of-phase signals which controls the RC filter circuits of the phase shifters and the other responds to the in-phase signals which controls the output summing junction of the notch filter. Finally, a feedforward type of simultaneous tuning is accomplished by ganging the oscillator frequency adjustment with the analyzer.

Journal ArticleDOI
TL;DR: In this article, a simple method of realizing the distributed RC () notch filter is discussed, which uses components which are readily available in an undergraduate laboratory, and experimental results obtained with the structure show reasonably good agreement with theory.
Abstract: In this communication, a simple method of realizing the distributed RC () notch filter is discussed. It uses components which are readily available in an undergraduate laboratory. Experimental results obtained with the structure show reasonably good agreement with theory.

Journal ArticleDOI
TL;DR: In this article, a second-order active all-pass filter is realized with three op. amp. biquad circuit, and the tunability of the filter is achieved by the use of periodically-switched conductances within the circuit in which the regulation of the switching parameter allows the independent adjustment of the delay characteristics.
Abstract: A second-order active all-pass filter is realized with three op. amp. biquad circuit. The tunability of the filter is achieved by the use of periodically-switched conductances within the circuit in which the regulation of the switching parameter allows the independent adjustment of the delay characteristics. It is shown that the maximum delay time and its corresponding frequency are adjustable independently by changing the ratio of the on-duration in a period to the period of switching. The electronically tunable active all-pass filter can be used for data transmission systems because of its sufficient flexibility of adjustment.