Showing papers on "Voltage-controlled filter published in 1974"

Transversal frequency filter

Abstract: A charge-transfer transversal filter and method of use is provided. In one aspect of the invention a handpass filter is provided where the center frequency of the bandpass is variable responsive to the clock rate applied to the charge-transfer devices. In a different aspect of the invention a matched filter for a chirp signal is provided. The filter requires a minimum number of Nyquist samples by including the provision of a clock rate which varies responsive to the frequency sweep of the input chirp signal. A method for detecting a chirp signal is provided which includes the step of selectively varying the clock rate applied to a charge-transfer shift register responsive to the frequency variations of a selected chirp signal.

An Algorithm for High-Speed Digital Filters

Abstract: This paper describes an algorithm that is suitable for fast implementations of nonrecursive and recursive digital filters. High speed is realized at the expense of memory; however, the memory-speed tradeoff is flexible so that many hardware and software implementations are practical. When memory is not limited, the time required to compute a filter output value is independent of the order of the filter.

Electronic musical instrument capable of generating tone signals having the pitch frequency, tone color and volume envelope varied with time

Abstract: In response to a pitch determining voltage obtained by key operation, a voltage controlled oscillator generates a tone signal having a pitch frequency corresponding to the note of the operated key. The tone signal, after a tone color is imparted by a voltage controlled filter, is supplied to a voltage controlled amplifier. The voltage controlled oscillator, voltage controlled filter and voltage controlled amplifier are controlled, during key depression and key release times, by control voltage waveforms varied with time. This causes the pitch, tone color and envelope of the tone signal to be transiently varied. An electronic musical instrument according to this invention may be constituted either as a monophonic type having a single voltage controlled oscillator or as a polyphonic type having a plurality of voltage controlled oscillators by using a key assigner.

Programmable Bandpass Filter and Tone Generator Using Bucket-Brigade Delay Lines

Abstract: Bucket-brigade devices have been used to build a new type of active filter that is equivalent to a second-order digital filter without the need for complex analog-to-digital conversion. The filter response characteristics, i.e., center frequency and bandwidth, depend on the circuit parameters of gain and clock frequency, both of which may be electronically controlled. By using a variable clock signal, 1023 frequencies can be accurately selected by the proper setting of ten switches. The selected clock frequency uniquely determines the center frequency of the bucket-brigade filter. The programmable feature of the clock circuit, therefore, allows the convenient selection of the center frequency of the bandpass filter. A slight modification to the programmable bandpass filter converts it into a programmable oscillator. Thus, any one of 1023 tones can be generated by the proper setting of the switches. A device that exhibits both filter and oscillator functions has been demonstrated in the laboratory.

Low pass nonrecusine digital filter

Abstract: A digital filter having a cut-off frequency of fc to which code words of a frequency fs are applied and which supplies code words at a frequency of f's The filter comprises a first digital filter section supplying numbers having a reduced frequency fm and whose output is directly coupled to an interpolating digital filter supplying the outgoing numbers of the filter at the frequency f's The first filter section and the interpolating digital filter are each built up as a digital filter having a cut-off frequency of fm/2

Wide dynamic range voltage controlled filter for electronic musical instruments

Abstract: A voltage controlled filter for an electronic synthesizer incorporates a plurality of individual voltage controlled filter stages connected in cascade with a variable feedback interconnecting the input and output stages. Each of the stages is controlled by application of a series of pulses, with the period between successive pulses determining the cutoff frequency of the filter. Application of pulses to the filter stages at different pulse repetition rates changes the cutoff frequency of the filter and modifies the relative amplitudes of different frequency components of an audio signal to be passed by the filter. The filter is suited for use with high level signals and provides an extremely wide dynamic range through a very high signal-to-noise ratio.

CCD selective transversal filter

Abstract: A charge coupled device to provide a multi-channel selective transversal filter in which a plurality (N) of channels are sequentially processed in a common transversal filter unit to provide a desired transfer function such as a high pass filter. The analog signals from a plurality of sources or channels are fed into the selective transversal filter in serial fashion with the signal from each channel being nondestructively sampled and multiplied by appropriate weighting coefficients as provided by split electrodes separated by (N-1) charge coupled device storage bits. By having storage electrodes between the split electrodes equal to the number of input channels, the split electrodes, which provide the output signals, operate upon signal information from one channel at a time. The displacement current differences between the two halves of all of the split electrodes provide output signals having the desired filter characteristics. The transversal filter devices in accordance with the invention may be operated in a single phase clock mode or in other clock modes. The filter may have a tuning capability to modify the filter response by providing a variation of the clock frequency applied to the electrodes.

Self-adaptive equalizer for multilevel data transmission according to correlation encoding

Abstract: A self-adaptive equalizer comprises a transversal filter wherein the attenuators are adjusted with reference to the output signals of the filter. For use in a multilevel data transmission system according to correlative encoding, a first filter removes the correlation encoding from the transversal filter outputs. Means is provided for producing binary signals representative of the signs of the first filter outputs. A second filter encodes the binary signals in accordance with the correlative encoding. The attenuators are adjusted in compliance with the respective products of the difference between one each of the second and transversal filter outputs and the signals derived from those taps of the delay line of the transversal filter to which the relevant attenuators are connected.

N-pole filter circuit having cascaded filter sections

Abstract: The n-pole filter preferably has four filter circuits cascaded in series. Each of the filter circuits is preferably a low-pass filter circuit and each has a controllable frequency response which is variably controlled from a common current or voltage source. Each filter circuit includes a transconductance circuit and inverting operational amplifier. A feedback resistor couples between the first and last filter circuits and is adjustable to provide different amounts of resonance.

Electrical current frequency filter circuit having parallel filter branches

Abstract: A filter circuit which comprises first and second parallel coupled filter branches each including a first multiplier, an intermediate frequency filter, and a second multiplier, respectively, coupled in series. A signal generator generates two output signals which are linearly independent of each other at a frequency which is equal to that of an input signal which is to be passed by the filter branches, and has a pair of output terminals coupled to the first multipliers of the filter branches for transmitting these output signals thereto. An adder is coupled to the second multipliers of the filter branches and generates an output signal which forms the output signal of the filter circuit. An adjustable signal feedback means is coupled to the output of the adder and to the inputs of the first multipliers of the filter branches for adjusting the bandwidth of the filter circuit. In an alternative embodiment of the invention, two pairs of identical filter branches are series coupled to form the filter circuit, with the adder of the second pair of filter branches generating the output signal of the filter circuit and being coupled to the signal feedback means of the circuit.

Arrangements for simulating inductance and filter networks incorporating such improvements

Abstract: A filter network particularly suitable for construction in micro-electronic circuitry for application in telephony systems is formed by simulating inductance in a circuit arrangement incorporating only resistance, capacitance and amplifying elements. The symmetry of the circuit arrangement and coupling into the filter network simplifies fabrication and reduces the number of amplifiers previously required to perform similar filter functions. The filter networks may be built up by coupling a chain of circuit arrangements each including two unity gain amplifiers having a series resistor/capacitor feedback network and a non-inductive element interconnecting the two amplifier feedback networks.

Filter arrangement for a converter circuit

Abstract: An improved filtering arrangement for a converter circuit in which a highpass filter, tuned to have a cutoff frequency which is less than the lowest harmonic to be filtered is provided instead of the customary plurality of filters tuned to individual harmonic currents. In a 12 pulse converter circuit, at least one highpass filter which is tuned to filter out harmonics starting with the fifth harmonic and which has a resonant frequency above the 11th harmonic is used.

Second-order canonical active filter

Abstract: A high-pass notch filter with variable gain that may be greater than unity is realized using a differential amplifier and only two capacitors that can be equal. The transmission zero and pole frequency are completely independent of the amplifier d-c gain. Three embodiments of the filter are illustrated, thus extending the available range of the gain to cover all requirements.

A Compact Channel-Dropping Filter for Stripline and Microwave Integrated Circuits

Abstract: A compact channel-dropping filter geometry is described that is particularly suited for stripline and microwave integrated circuits (MIC). The channel-dropping filter is comprised of a hairpin bandpass filter and a new bandstop filter, referred to herein as a folded-line bandstop filter. Design parameters for the latter filter for a range of bandwidths are tabulated. Analytical and experimental data for a trial channel-dropping filter are presented and discussed.

Electronic musical instrument capable of generating tone signals having pitch frequency, tone color and volume envelope varied with time

Abstract: An electronic musical instrument comprising a voltage controlled oscillator, a voltage controlled filter, a voltage controlled amplifier and envelope generators. An output envelope of the envelope generator has various parameters such as rise time and decay time or times. The envelope generator is of the voltage controlled type so that the parameters of the output envelope of the envelope generator are controllable in response to parameter controlling voltages from a parameter controlling voltage generator. In an attempt to enhance performance effects a switch circuit is provided, in accordance with the invention, to interchange between a rise time controlling voltage and a decay time controlling voltage which are both coupled from the parameter controlling voltage generator to the envelope generator.

A Class of Waveguide Filters for Over-Moded Applications

Abstract: As the frequency spectrum extends to the millimeter wave range, the rapid rise in intrinsic loss and the diminishing physical dimensions greatly curtail the usefulness of conventional waveguide filters in dominant mode waveguide The incentive for designing filters in over-moded waveguide is all too apparent However, filter design in over-moded waveguide faces challenging design criteria, such as mode conversion loss and intrinsic loss, ease of being analyzed and synthesized, and feasibility for economical fabrication A filter structure is presented which fulfills all aspects of the design objectives The structure involves a type of discontinuity which is not only free from mode conversion but also extremely simple to characterize analytically The latter renders feasible the use of available filter synthesis techniques While the proposed filter structure can be designed either as a bandpass filter, a bandstop filter or a low-pass filter in an over-moded uniform waveguide of arbitrary cross section, for illustration purposes only the low-pass filter in over-moded circular waveguide is discussed in great detail Design theories are presented which allow the proposed structure to be designed either by the image method or by operating parameter filter synthesis Excellent agreement between the theory and measurements made on filter models is shown

Aperture correction circuit for television

Abstract: A vertical aperture correction circuit for television in which two cheap narrow-band delay circuits are used for giving a line period delay by means of signal modulation. High-frequency video information is applied through a highpass filter to an adder stage to which furthermore the low-frequency video information delayed over one line period and the aperture correction signal are applied. The highpass filter may be formed with a third narrow-band delay circuit as a bandpass filter.

Active RC low-pass filter suitable for integration

Abstract: A canonic active RC low-pass filter having both capacitors earthed is given. The ω0 and the Q sensitivities with respect to all circuit components are derived. A unique feature of the circuit is that uo, is absolutely insensitive to the gain-bandwidth of the operational amplifiers.

Low pass filter apparatus

Abstract: The combination of a linear phase bandpass filter between a modulator and demodulator wherein the equivalent of a lowpass filter is produced by increasing the frequency of the signal to be lowpass filtered by carrier modulating it, bandpass filtering the increased frequency signal and demodulating the bandpass filtered signal to produce a lowpass filtered output having linear phase characteristics.

Navigation receiver with doppler filter gating

Abstract: A navigation guidance receiving system for use with a Doppler navigation beacon of the type comprising a commutated linear array for producing a simulated Doppler effect. The receiving system includes a wideband Doppler beat waveform information filter and measurement circuits. Means are also provided to gate the filter output synchronously to allow dissipation of the filter transient response. The result is reduced filter frequency "pulling" and reduced measurement error due to the effect of multipath signals having beat frequencies in the filter rejection band.

Active RC high selectivity notch filter

Abstract: A general configuration for realizing a high Q notch filter is given. The circuit has a very high input impedance and a very low output impedance. The frequency limitation equations based on the one-pole roll-off model of the operational amplifier are given.

Folded-Line and Hybrid Folded-Line Bandstop Filters

Abstract: The feasibility of a new, compact bandstop filter geometry is demonstrated theoretically and experimentally. The filter geometry is particularly suited for stripline and MIC fabrications in that grounding is not required for any part of the filter. Hybrid folded-line geometries allow the filter designer substantial flexibility in choosing a suitable shape factor without significantly effecting the filter's electrical characteristics. The filter geometry is suitable for narrow bandwidth (provided capacitive coupled stubs are used) to wide bandwidth applications.

Waveguide Filters for Over-Moded Applications

Abstract: As the frequency spectrum extends to the millimeter wave range, the rapid rise in intrinsic loss and the diminishing physical dimensions greatly curtail the usefulness of conventional waveguide filters in dominant mode waveguide. The incentive for designing filters in over-moded waveguide is all too apparent. How- ever, filter design in over-moded waveguide faces challenging design criteria, such as mode conversion loss and intrinsic loss, ease of being analyzed and synthesized, and feasibility for eco- nomical fabrication. A filter structure is presented which fulfills all aspects of the design objectives. The structure involves a type of discontinuity which is not only free from mode conversion but also extremely simple to characterize analytically. The latter renders feasible the use of available filter synthesis techniques. While the proposed filter structure can be designed either as a bandpass filter, a bandstop filter or a low-pass filter in an over-moded uniform wave- @de of arbitrary cro& section, for illustration purposes only the low-pass filter in over-moded circular waveguide is discussed in great detail. Design theories are presented which allow the proposed structure to be designed either by the image method or by operating parameter filter synthesis. Excellent agreement between the theory and measurements made on filter models is shown.

One Hundred Channel Selectable Surface Wave Bandpass Filter

Abstract: Surface wave multichannel bandpass filters such as the selectable filters, filter trees, or filter banks provide a large number of bandpass filter channels with relatively few transducers. Among major systems applications are frequency-hopped receivers, spread-spectrum equipment,and multichannel multiplex systems. Synthesis of more than 100 bandpass responses of varying center frequency and varying bandwidth with nominally 20 transducers is detailed.

Automatic Measurement System for a Multichannel Digitally Tuned Bandpass Filter

Abstract: A system is described that automatically and rapidly measures the electrical parameters for each channel in a multichannel digitally tuned bandpass filter. The performance of the filter over its entire tuning range is determined from the individual channel frequency characteristics. Channel frequency characteristics are displayed to summarize the overall performance of the filter and in such a manner as to indicate the channel tuning adjustments necessary to meet the filter specifications.

A programmable bandpass filter and tone generator using bucket-brigade delay lines

Abstract: Bucket-brigade devices have been used to build a new type of active filter that is equivalent to a second-order digital filter without the need for complex analog-to-digital conversion. The x It) filter response characteristics, i.e., center frequency and bandwidth, + I depend on the circuit parameters of gain and clock frequency, both e2(t- U of which may be electronically controlled. + By using a variable clock signal, 1023 frequencies can be ac- I e0%, curately selected by the proper setting of ten switches. The selected clock frequency uniquely determines the center frequency of the bucket-brigade filter. The programmable feature of the clock circuit, DELAND therefore, allows the convenient selection of the center frequency u It-T,) of the bandpass filter. A slight modification to the programmable bandpass filter converts it into a programmable oscillator. Thus, any one of 1023 tones can be generated by the proper setting of the switches. A device that ex- D hibits both filter and oscillator functions has been demonstrated in the laboratory.

A systematic method of generating biquadratic filter sections

Abstract: Biquadratic filter sections for use alone or as building blocks for higher-order active filters can be generated by a simple two-step synthesis technique The first step is aimed at synthesis of the poles realizing not only the polo-Q and resonant frequency, but also the type of feedback present in the circuit. Since the type of feedback can be specified, circuits with predictable gain and sensitivity properties can be synthesized. The second step results in realizing the appropriate numerator without affecting the polo-producing network, The technique has been used to realize numerous now active filter circuits.

Simulation of a voltage-controlled filter

Abstract: A new technique for voltage-controlled filtering is presented in this work. The results to be expected from the technique are analyzed by simulation since the filter can be described analytically only through approximations. The filtering technique is based on a linear system with periodically operated synchronous switches. A hardware model of the filter was built and the digital simulation outputs are compared with those obtained with the hardware. Filtering performances in the simulation and in the hardware were in close agreement. Though only Butterworth filters were considered, the method is expected to have much broader appli cations.

Active filter realization of biquadratic transfer function

Abstract: The realization of quadratic transfer functions by an active band-pass filter is described. The hybrid-integrated circuit used consists of a three-terminal passive network, connected to a high-gain inverting amplifier. A design procedure for minimizing the gain–sensitivity product is given. By interchanging two connections between the passive network and the amplifier, the band-pass is converted into a band-stop characteristic. A pair of such circuits may be cascaded to generate a generalized biquadratic transfer function. Parasitic singularities due to each circuit are eliminated through pole-zero cancellation between the cascaded filters. In this manner, a wide range of transfer functions is realizable. A low-pass or a notch filter can be obtained by adding an isolating stage.