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Patent

Square wave/sine wave conversion

TLDR
In this article, a low-pass filter is used to convert a square wave to sine wave converter using a low pass filter, whose cut-off frequency is variable in accordance with the frequency of the square wave applied to it.
Abstract
A square wave to sine wave converter using a low-pass filter. The cut-off frequency of the filter is variable in accordance with the frequency of the square wave applied to it. This is achieved by the effective value of a frequency-determining impedance in the filter varying with the square wave frequency. A resistor is switched in and out of circuit at a rate which is at least a multiple of 100 of the square wave frequency.

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Citations
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Patent

20 Hz ring generator using high frequency PWM control

TL;DR: In this article, a ring signal generator with a PWM circuit was proposed, which produces a VRMS ring signal from a DC power supply using a pair of switches controlled by pulse width modulation (PWM) circuit.
Patent

Double-balanced sinusoidal mixing phase interpolator circuit and method

TL;DR: In this paper, a double-balanced sinusoidal mixing phase interpolator circuit is proposed, where the sinusoid weighting provides uniformly spaced phase steps in the phase interpolation (PI) output.
Patent

Programmable sound circuit for electronic games

Earl Vickers
TL;DR: In this paper, a sound generator for use with microprocessor controlled amusement games includes a programmable sound generator and programmable filters, which utilize duty-cycle-controlled resistors to provide analog filtering under microprocessor control.
Patent

Square to pseudo-sinusoidal clock conversion circuit and method

TL;DR: In this paper, a square wave to pseudo-sinusoidal clock conversion circuit comprises first and second stages, where the first stage includes a cross-coupled differential pairs input gain stage having positive and negative input sides.
Patent

Sine-shaping circuit

TL;DR: In this article, a circuit for converting a triangular waveform into a sinusoidal waveform using the non-linear transfer characteristic of a first transistor differential amplifier is presented. But the circuit is not suitable for the case of a single-input single-output (SIMO) circuit.
References
More filters
Patent

Voltage controlled electronic filter

TL;DR: In this paper, the response characteristics of an electronic filter are automatically adjusted as a function of the magnitude of an applied DC voltage to permit the same filter to be used for varying applications.
Patent

Active filter network having a variable center frequency

G Hurtig
TL;DR: In this article, the authors considered an active filter network with a variable center frequency, where the output terminal of the network is coupled to the first and second switching terminals of the active filter.
Patent

Adjustable time constant operating circuit

B Katz
TL;DR: In this paper, a switch means are provided to periodically interrupt the resistive feedback path of a differentiating circuit or input path of an integrating circuit to adjust the time constant of an operating circuit including an operational amplifier.