US3764924A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Synchronous detection system
Assignee: United States Department of the Navy
•
Filing: 1972-05-08
•
Granted: 1973-10-09
•
Expires: 1992-05-08
Abstract
Abstract A periodic signal to be detected plus associated noise components are amplified, filtered and applied as an input to a pair of chopper switches gated synchronously with the signal to switchably chop the signal into phase-locked, complementary half wave portions. In effect, each of the chopper outputs has a direct current waveform with one of the outputs being opposite in sign to the other. The chopper outputs then are applied as separate inputs to the inverting and non-inverting inputs of a differential, low-pass, narrowband filter to eliminate random noise as well as any common errors present on both of half-wave inputs. The output of the low-pass filter is a single-polarity dc voltage which being proportional to the amplitude of the signal to be detected, provides the means for detecting the signal. A reference signal is used to gate the choppers and preferably it is processed by an integrated logic circuit to provide a pair of complementary gating signals one of which is with the input signal and the other 180* out of phase. The chopper switches may be MOSFET components interconnected in a series-shunt configuration which permits very rapid switching to provide distortion-free operation over a wide range of signal frequencies (1-5MHz).
Inventors
- 👤 L Caplan
- 👤 R Stern
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 00:59
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/02; H03D1/04
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
189 words
A synchronous detector for detecting a wide range of periodic input signals buried in a random noise background, comprising: continuously-active input signal and noise amplifying and frequency-filtering means for processing the entire periodic input to produce a narrow-band frequency signal and noise output corresponding to said entire input, a reference signal source providing a reference signal having a frequency corresponding to that of the input signal to be detected, reference signal processing means adapted to generate an output signal formed into a pair of complementary square-wave gating signals one of which is in phase with said amplified and filtered input signal and 180* out of phase with the other, and mixer-detector means controlled by said generated reference signal output for converting said narrow band signal and noise output into a direct current voltage output proportional to the input signal amplitude whereby said input signal can be detected by monitoring said proportional DC output, said mixer-detector including a pair of switches each being gateably-controlled by a separate one of said complementary gating signals for converting said signal and noise narrow band output into a pair of half-wave complementary signal outputs.
Claim 2
Dependent Claim
189 words
A synchronous detector for detecting a wide range of periodic input signals buried in a random noise background, comprising: continuously-active input signal and noise amplifying and frequency-filtering means for processing the entire periodic input to produce a narrow-band frequency signal and noise output corresponding to said entire input, a reference signal source providing a reference signal having a frequency corresponding to that of the input signal to be detected, reference signal processing means adapted to generate an output signal formed into a pair of complementary square-wave gating signals one of which is in phase with said amplified and filtered input signal and 180* out of phase with the other, and mixer-detector means controlled by said generated reference signal output for converting said narrow band signal and noise output into a direct current voltage output proportional to the input signal amplitude whereby said input signal can be detected by monitoring said proportional DC output, said mixer-detector including a pair of switches each being gateably-controlled by a separate one of said complementary gating signals for converting said signal and noise narrow band output into a pair of half-wave complementary signal outputs.
Claim 3
Dependent Claim
19 words
The detector of claim 1 wherein said means for forming said complementary gating outputs includes an integrated NAND-gate circuit.
Claim 4
Dependent Claim
38 words
The detector of claim 2 wherein said reference signal processing means includes a phase-adjust circuit having an output, and means for squaring the output of said phase-adjust circuit, said squaring means providing an input for said NAND-gate circuit.
Claim 5
Dependent Claim
49 words
The detector of claim 1 wherein said mixer-detector further includes: a differential low-pass narrow-band active filtering means having inverting and non-inverting inputs coupled one to one of said pair of half-wave signal outputs and the other to the other of said pair for producing said direct current voltage output.
Claim 6
Dependent Claim
38 words
The detector of claim 4 wherein each of said pair of switches includes a pair of chopper-mixer switching circuit elements interconnected in a series-shunt configuration for promoting rapid switching and for shunting stray signals passing the series element.
Claim 7
Dependent Claim
18 words
The detector of claim 5 wherein said switching elements are MOSFET components having gate, source and drain electrodes.
Claim 8
Dependent Claim
19 words
The detector of claim 5 wherein said means for forming said complementary gating outputs includes an integrated NAND-gate circuit.
Claim 9
Dependent Claim
70 words
The detector of claim 5 wherein said input signal and noise amplifying and filtering means includes: a variable band-pass active filtering means having an input signal frequency operating range extending from about 1 hertz to at least 5 megahertz, and manually-operable switch means for variably controlling the bandwidth of the bandpass to produce a relatively narrow-band filter output centered at about the frequency of the input signal to be detected.
Claim 10
Dependent Claim
76 words
The detector of claim 8 wherein said band-pass filtering means includes: an active low-pass filter, an active high-pass filter, and independently operable switch means for each of said active filters, each of said switch means being manually controllable for varying the cut-off frequency of each of the filters to produce a relatively narrow-band filter means output whereby an operator can select the band-pass center frequency and bandwidth and circuit Q while maintaining a relatively constant gain.
Claim 11
Dependent Claim
74 words
The detector of claim 8 wherein said pair of chopper-mixer switching elements are MOSFET components having gate, source and drain electrodes, said narrow-band filter output of the input signal and noise filtering means being applied to the source electrode of each of said MOSFET components, and said pair of complementary square-wave gating signals derived from said reference processing means being applied one to each of the gate electrodes of said pair of MOSFET components.
Claim 12
Dependent Claim
53 words
The detector of claim 10 wherein said input signal and noise amplifying and filtering means includes: a single variable-gain amplifier directly receiving the input signal to be detected, and an output amplifier having an input coupled to said band-pass filtering means output, said single amplifier providing an input for said band-pass filtering means.
Claim 13
Dependent Claim
17 words
The detector of claim 11 wherein said output amplifier includes manually-controllable means for zeroing the output voltage.
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) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |