US4542346A
Expired / Lapsed
US
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Wide-range lock-in amplifier
Assignee: United States, AS REPRESENTED BY UNITED STATED DEPARTMENT OF ENERGY
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Filing: 1982-12-07
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Granted: 1985-09-17
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Expires: 2002-12-07
Abstract
Abstract A lock-in amplifier is provided which allows detection of a signal buried in noise without preprocessing of the input signal. An analog signal multiplier is used to obtain a dc output which is the product of the signal being detected and a high-purity sine wave signal. A reference signal of a known selectable frequency is applied to a sine-wave generator to generate the sine wave of the same frequency. The sine wave is applied to a multiplier through a phase shift arrangement to allow the detection of both amplitude of the detected signal and the phases relative to the reference signal. The multiplier output is filtered by a low-pass filter to eliminate unwanted frequency components from the output signal.
Inventors
- 👤 David R. McNeilly
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:59
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/22; H03D1/2245; H03D1/2254
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
249 words
A lock-in amplifier for detecting a particular frequency component of an input signal, comprising: a first sine wave generating means responsive to an input reference signal at an input thereof having a frequency equal to the frequency of said component of said input signal to be detected for generating a first sine wave reference signal at an output thereof which is equal in frequency to and 90° out-of-phase with said input reference signal; a second sine wave generating means responsive to the output of said first sine wave generating means for generating a second sine wave reference signal at an output thereof which is equal in frequency to and in phase with said input reference signal; a first multiplier means having a first input for receiving said input signal and a second input for receiving said first sine wave reference signal for generating a first dc signal at an output thereof which is a product of said component of said input signal to be detected and said first sine wave reference signal; a second multiplier means having a first input for receiving said input signal and a second input for receiving said second sine wave reference signal for generating a second dc signal at an output thereof which is a product of said component of said input signal to be detected and said second sine wave reference signal; and first and second low-pass filtering means connected respectively in series with the outputs of said first and second multiplier means.
Claim 2
Dependent Claim
249 words
A lock-in amplifier for detecting a particular frequency component of an input signal, comprising: a first sine wave generating means responsive to an input reference signal at an input thereof having a frequency equal to the frequency of said component of said input signal to be detected for generating a first sine wave reference signal at an output thereof which is equal in frequency to and 90° out-of-phase with said input reference signal; a second sine wave generating means responsive to the output of said first sine wave generating means for generating a second sine wave reference signal at an output thereof which is equal in frequency to and in phase with said input reference signal; a first multiplier means having a first input for receiving said input signal and a second input for receiving said first sine wave reference signal for generating a first dc signal at an output thereof which is a product of said component of said input signal to be detected and said first sine wave reference signal; a second multiplier means having a first input for receiving said input signal and a second input for receiving said second sine wave reference signal for generating a second dc signal at an output thereof which is a product of said component of said input signal to be detected and said second sine wave reference signal; and first and second low-pass filtering means connected respectively in series with the outputs of said first and second multiplier means.
Claim 3
Dependent Claim
16 words
The lock-in amplifier of claim 1 wherein said first and second multiplier means are analog multipliers.
Claim 4
Dependent Claim
34 words
The lock-in amplifier as set forth in claim 2 wherein a variable frequency reference signal generator is connected to the input of said first sine wave generating means to provide said input reference signal.
Claim 5
Dependent Claim
102 words
The lock-in amplifier as set forth in claim 1 wherein each of said first and second sine wave generating means includes means for generating a square wave signal in phase with the input signal applied thereto, a phase-locked loop connected to receive said square wave signal, and a voltage controlled oscillator coupled with said phase-locked loop so that a sine wave signal is generated at the output of said voltage controlled oscillator having a frequency equal to the frequency of said square wave applied to the input of said phase-locked loop and phase shifted 90° relative to said square wave input signal.
References Cited (Backward Citations)
US4200801A
Cited
US4426622A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-09-16 | 1989-03-18 | 1989-09-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-09-16 | 1993-03-18 | 1993-09-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-09-16 | 1997-03-18 | 1997-09-17 | $7700.00 | Window Closed / Lapsed |