US3714593A
Expired / Lapsed
US
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Synchronous demodulator having an improved driving circuit
Assignee: Keithley Instruments LLC
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Filing: 1971-11-24
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Granted: 1973-01-30
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Expires: 1991-11-24
Abstract
Abstract A driving circuit is disclosed for a synchronous demodulator having first and second actuatable switching means, such as field effect transistors, which are to be alternately actuated by the driving circuit at a reference frequency for purposes of demodulating an A.C. signal containing noise and a signal of interest. The driving circuit serves to receive a reference signal at the reference frequency and to provide therefrom first and second drive signals displaced in phase by 180* for alternately actuating the first and second switching means. The phase relationship between the drive signals and the reference signal is varied independently of variations in the reference frequency. This is accomplished with circuitry which serves to provide a ramp signal which varies from a first level toward a second level in synchronism with the reference frequency, and to provide an output pulse whenever the ramp signal attains a threshold level. The threshold level is adjustable to vary the phase relationship between the output signal pulse and the reference signal.
Inventors
- 👤 R Kime
- 👤 W Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 11:50
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/02; H03D3/18
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
189 words
A driving circuit for a synchronous demodulator having first and second actuatable switching means to be alternately actuated by the driving circuit at a reference frequency for demodulating an AC signal containing noise and a signal of interest at said reference frequency and providing a DC output signal representative of said signal of interest wherein said driving circuit includes: means for receiving a reference signal exhibiting said reference frequency and providing first and second drive signals displaced in phase by 180* and at said reference frequency for alternately actuating said first and second switching means, respectively, and including means for varying the phase relationship between said drive signals and said reference signal independently of variations in the frequency of said reference signal; said phase varying means including means for providing a ramp signal which varies from a first level toward a second level at a frequency in synchronism with said reference frequency, means for providing an output signal pulse when said ramp signal attains a threshold level, and means for varying said threshold level to thereby vary the phase relationship between said output signal pulse and said reference signal.
Claim 2
Dependent Claim
189 words
A driving circuit for a synchronous demodulator having first and second actuatable switching means to be alternately actuated by the driving circuit at a reference frequency for demodulating an AC signal containing noise and a signal of interest at said reference frequency and providing a DC output signal representative of said signal of interest wherein said driving circuit includes: means for receiving a reference signal exhibiting said reference frequency and providing first and second drive signals displaced in phase by 180* and at said reference frequency for alternately actuating said first and second switching means, respectively, and including means for varying the phase relationship between said drive signals and said reference signal independently of variations in the frequency of said reference signal; said phase varying means including means for providing a ramp signal which varies from a first level toward a second level at a frequency in synchronism with said reference frequency, means for providing an output signal pulse when said ramp signal attains a threshold level, and means for varying said threshold level to thereby vary the phase relationship between said output signal pulse and said reference signal.
Claim 3
Dependent Claim
189 words
A driving circuit for a synchronous demodulator having first and second actuatable switching means to be alternately actuated by the driving circuit at a reference frequency for demodulating an AC signal containing noise and a signal of interest at said reference frequency and providing a DC output signal representative of said signal of interest wherein said driving circuit includes: means for receiving a reference signal exhibiting said reference frequency and providing first and second drive signals displaced in phase by 180* and at said reference frequency for alternately actuating said first and second switching means, respectively, and including means for varying the phase relationship between said drive signals and said reference signal independently of variations in the frequency of said reference signal; said phase varying means including means for providing a ramp signal which varies from a first level toward a second level at a frequency in synchronism with said reference frequency, means for providing an output signal pulse when said ramp signal attains a threshold level, and means for varying said threshold level to thereby vary the phase relationship between said output signal pulse and said reference signal.
Claim 4
Dependent Claim
189 words
A driving circuit for a synchronous demodulator having first and second actuatable switching means to be alternately actuated by the driving circuit at a reference frequency for demodulating an AC signal containing noise and a signal of interest at said reference frequency and providing a DC output signal representative of said signal of interest wherein said driving circuit includes: means for receiving a reference signal exhibiting said reference frequency and providing first and second drive signals displaced in phase by 180* and at said reference frequency for alternately actuating said first and second switching means, respectively, and including means for varying the phase relationship between said drive signals and said reference signal independently of variations in the frequency of said reference signal; said phase varying means including means for providing a ramp signal which varies from a first level toward a second level at a frequency in synchronism with said reference frequency, means for providing an output signal pulse when said ramp signal attains a threshold level, and means for varying said threshold level to thereby vary the phase relationship between said output signal pulse and said reference signal.
Claim 5
Dependent Claim
27 words
A driving circuit as set forth in claim 1, including reference frequency measuring means for providing an output indication as to the frequency of said reference signal.
Claim 6
Dependent Claim
39 words
A driving circuit as set forth in claim 2, wherein said frequency measuring means includes a frequency to voltage conversion means for converting said reference signal into a DC level signal exhibiting a magnitude proportional to said reference frequency.
Claim 7
Dependent Claim
35 words
A driving circuit as set forth in claim 1, wherein said phase varying means includes means for providing a visual indication as to the phase relationship between said signal of interest and said reference signal.
Claim 8
Dependent Claim
29 words
A driving circuit as set forth in claim 1, including means for providing a second output signal pulse displaced in phase by 180* from said first output signal pulse.
Claim 9
Dependent Claim
30 words
A driving circuit as set forth in claim 5, including output means for providing said first and second driving signals in dependence upon said first and second output signal pulses.
Claim 10
Dependent Claim
47 words
A driving circuit as set forth in claim 4, wherein said visual indicating means includes a calibrated dial connected to said threshold varying means to provide a visual indication of the phase relationship between said driving signals and said reference signal and, hence, said signal of interest.
Claim 11
Dependent Claim
29 words
A driving circuit as set forth in claim 1, including means for controlling the slope of said ramp signal as a function of the frequency of said reference signal.
Claim 12
Dependent Claim
49 words
A driving circuit as set forth in claim 1 including means for providing a control signal dependent upon the frequency of said reference signal, and said ramp signal means being controlled by said control signal so that the slope of said ramp signal is dependent upon the reference frequency.
Claim 13
Dependent Claim
50 words
A driving circuit as set forth in claim 1 wherein said ramp signal providing Means includes an integrating capacitor which charges at a rate dependent upon the magnitude of a control signal applied thereto, and means for providing a said control signal having a magnitude proportional to the reference frequency.
Claim 14
Dependent Claim
36 words
A driving circuit as set forth in claim 10, wherein said control signal providing means includes a frequency to voltage converter for providing an output voltage having a magnitude which varies proportional to said reference frequency.
Claim 15
Dependent Claim
21 words
A driving circuit as set forth in claim 10, wherein said ramp signal providing means is a linear ramp generator means.
Claim 16
Dependent Claim
47 words
A driving circuit as set forth in claim 10, wherein said ramp signal providing means includes actuatable switching means for, when actuated, connecting said integrating capacitor to receive said control signal so as to be charged at a rate dependent upon the magnitude of said control signal.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-01-30 | 1976-07-31 | 1977-01-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-30 | 1980-07-31 | 1981-01-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-30 | 1984-07-31 | 1985-01-30 | $7700.00 | Window Closed / Lapsed |