US4250455A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Square wave/sine wave conversion
Assignee: Her Majesty the Queen in Right of Canada
•
Filing: 1978-08-25
•
Granted: 1981-02-10
•
Expires: 1998-08-25
Abstract
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.
Inventors
- 👤 Bryce D. Davis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:52
CPC Classifications
H; H03; H03B; H03B28/00
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
160 words
A square wave to sine wave converter having an input terminal adapted to receive a square wave at an input frequency and an output terminal adapted to provide a sine wave at an output frequency, comprising: a low pass filter connected between the input terminal and the output terminal, said low pass filter including an impedance whose effective value is determined by the input frequency of the square wave, the effective value of the impedance subsequently determining a cut-off frequency for said low pass filter; switching means connected to said impedance for modifying the value thereof, said switching means including a switch and said impedance in parallel with a series arrangement of a resistor and said switch; and generating means connected between the input terminal and the switching means, said generating means being operable to produce a train of narrow pulses for actuating said switch at a rate equal to a multiple of the input frequency of said square wave.
Claim 2
Dependent Claim
160 words
A square wave to sine wave converter having an input terminal adapted to receive a square wave at an input frequency and an output terminal adapted to provide a sine wave at an output frequency, comprising: a low pass filter connected between the input terminal and the output terminal, said low pass filter including an impedance whose effective value is determined by the input frequency of the square wave, the effective value of the impedance subsequently determining a cut-off frequency for said low pass filter; switching means connected to said impedance for modifying the value thereof, said switching means including a switch and said impedance in parallel with a series arrangement of a resistor and said switch; and generating means connected between the input terminal and the switching means, said generating means being operable to produce a train of narrow pulses for actuating said switch at a rate equal to a multiple of the input frequency of said square wave.
Claim 3
Dependent Claim
146 words
A square wave to sine wave converter, comprising: at least one low-pass filter connected in series to receive a square wave and produce a corresponding sine wave, each filter having a pair of composite resistor elements to determine the cut-off frequency; frequency multiplying means adapted to receive the square wave and provide a signal at a multiple of the frequency thereof; pulse shaping means responding to the aforesaid signal and producing a train of narrow pulses in synchronism therewith; and a switching circuit containing a plurality of switches each actuated in response to the occurrence of a pulse in said train of narrow pulses each composite resistor element consisting of a first resistor in parallel with a series arrangement of a second resistor and one of said plurality of switches whereby the cut-off frequency of each filter varies with the frequency of the received square wave.
Claim 4
Dependent Claim
146 words
A square wave to sine wave converter, comprising: at least one low-pass filter connected in series to receive a square wave and produce a corresponding sine wave, each filter having a pair of composite resistor elements to determine the cut-off frequency; frequency multiplying means adapted to receive the square wave and provide a signal at a multiple of the frequency thereof; pulse shaping means responding to the aforesaid signal and producing a train of narrow pulses in synchronism therewith; and a switching circuit containing a plurality of switches each actuated in response to the occurrence of a pulse in said train of narrow pulses each composite resistor element consisting of a first resistor in parallel with a series arrangement of a second resistor and one of said plurality of switches whereby the cut-off frequency of each filter varies with the frequency of the received square wave.
Claim 5
Dependent Claim
18 words
A converter as defined in claim 2 wherein each said low-pass filter is an active feedback low-pass filter.
Claim 6
Dependent Claim
145 words
A square wave to sine wave converter, comprising: a pair of active feedback low-pass filters connected in series to receive a square wave and produce a corresponding wave, each filter having a pair of composite resistor elements to determine the cut-off frequency. frequency multiplying means adapted to receive the square wave and provide a signal at a multiple of the frequency thereof, pulse generating means responsive to said signal to produce a train of narrow pulses in synchronism therewith, a switching circuit containing a plurality of switches each actuated in response to the occurrence of a pulse in said train of narrow pulses, each composite resistor element consisting of a first resistor in parallel with a series arrangement of a second resistor and one of said plurality of switches whereby the cut-off frequency of each filter varies with the frequency of the received square wave.
Claim 7
Dependent Claim
145 words
A square wave to sine wave converter, comprising: a pair of active feedback low-pass filters connected in series to receive a square wave and produce a corresponding wave, each filter having a pair of composite resistor elements to determine the cut-off frequency. frequency multiplying means adapted to receive the square wave and provide a signal at a multiple of the frequency thereof, pulse generating means responsive to said signal to produce a train of narrow pulses in synchronism therewith, a switching circuit containing a plurality of switches each actuated in response to the occurrence of a pulse in said train of narrow pulses, each composite resistor element consisting of a first resistor in parallel with a series arrangement of a second resistor and one of said plurality of switches whereby the cut-off frequency of each filter varies with the frequency of the received square wave.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-10 | 1984-08-11 | 1985-02-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-10 | 1988-08-11 | 1989-02-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-10 | 1992-08-11 | 1993-02-10 | $7700.00 | Window Closed / Lapsed |