Patent US3757203A successfully refreshed from Google Patents.
US3757203A
Expired / Lapsed
US
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Magnetometer for detection and indentification of immersed bodies
Assignee: Commissariat à l'Énergie Atomique et Aux Énergies Alternatives
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Filing: 1971-09-21
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Granted: 1973-09-04
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Expires: 1991-09-21
Abstract
Abstract A device for use with a differential magnetometer which is carried or towed by an aircraft is intended to determine whether a signal indicates the presence of a wreck or sub marine. The device comprises several bandpass filters whose frequencies are so selected that one of the filters provides an output higher than that of any filter outside a pre-determined frequency range which corresponds to the frequency spectrum of a typical body for a pre-determined speed of the aircraft, if such a body is present.
Inventors
- 👤 A Salvi
- 👤 G Chiron
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:05
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/15; G01V3/165
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
206 words
A system for processing the signal delivered by a differential magnetometer displaced by an aircraft along a level path and for detecting and indicating the presence of an immersed magnetic body, comprising: N stages connected in parallel to the output of said magnetometer, N being a predetermined integer greater than one, each of said N stages comprising in series: band pass filter means, first means coupled to said band pass filter means for detecting the envelope of the signals provided by said band pass filter, and second means coupled to said first means for detecting the maximum of said envelope; said band pass filter means of said N stages operating to divide a predetermined frequency band fo - f''o into sub-bands selected as a function of the altitude of said magnetometer and of the horizontal speed thereof; means coupled at the output of said N stages for comparing the maximum of said envelope as detected by said second means of each of said N stages and for indicating which maximum is the greatest; and decision means responsive to the occurence of the greatest maximum at a predetermined subrange in the band fo - f'' o for indicating the likelihood of the presence of an underwater body
Claim 2
Independent Claim
206 words
A system for processing the signal delivered by a differential magnetometer displaced by an aircraft along a level path and for detecting and indicating the presence of an immersed magnetic body, comprising: N stages connected in parallel to the output of said magnetometer, N being a predetermined integer greater than one, each of said N stages comprising in series: band pass filter means, first means coupled to said band pass filter means for detecting the envelope of the signals provided by said band pass filter, and second means coupled to said first means for detecting the maximum of said envelope; said band pass filter means of said N stages operating to divide a predetermined frequency band fo - f''o into sub-bands selected as a function of the altitude of said magnetometer and of the horizontal speed thereof; means coupled at the output of said N stages for comparing the maximum of said envelope as detected by said second means of each of said N stages and for indicating which maximum is the greatest; and decision means responsive to the occurence of the greatest maximum at a predetermined subrange in the band fo - f'' o for indicating the likelihood of the presence of an underwater body
Claim 3
Dependent Claim
20 words
A system ccording to claim 1, wherein all filters have the same ratio between their central frequency and their bandwidth.
Claim 4
Dependent Claim
54 words
A system according to claim 1, wherein the frequency bands of the filters are adjacent, the first filter covering a range of frequencies below fo and having an upper band limit equal to fo, and the same filter covering a range of frequencies higher than f''o and having a lower limit equal to f''o.
Claim 5
Dependent Claim
56 words
A system according to claim 3, wherein an aeroplane flies the magnetometer at a speed of about 100 meters per second and at an altitude between 100 and 400 metres, the frequency fo is 0.037 cps., the frequency f''o is 0.47 cps the filters have a sharpness of 2.5, and the number of filters is 8.
Claim 6
Dependent Claim
53 words
A system according to claim 1, wherein each band-pass filter consists of a low-pass filter and a high-pass filter in series, each of said low-pass and high-pass filters comprising RC cells in series connected by impedance matching means to a high-gain DC amplifier having a RC reaction loop providing a square gain curve.
Claim 7
Dependent Claim
71 words
A device according to claim 1, wherein each stage for detecting the envelope of the signals from each filter comprises a double wave rectifier unit, a differentiating unit, energized by said differentiating unit a trigger circuit a monovibrator controlled by said trigger and delivering opening pulses to a gate which charges a capacitor during the time when the gate is open as a result of signals supplied by the rectifier unit.
Claim 8
Dependent Claim
84 words
A system according to claim 1, wherein each stage for detecting the maxima Vi of the envelopes comprises an impedance matching unit fed by said unit, a gate differentiating means fed by said unit and which supplies opening pulses to a gate and actuates a flip flop, a monostable triggered by said flip flop and which delivers a pulse indicating the instant when the maximum is obtained, said gate when open enabling the signals delivered by the impedance matching unit to load a capacitor.
Claim 9
Independent Claim
131 words
A system accOrding toclaim 1, wherein the maxima-comparing and decision stage consists of (N - 1) double gates opened by pulses Ii switching the maxima Vi + 1 and Vi to the inputs of (N - 1) differential amplifiers outputting signals VI 1 - Vi to (N -2) monostables, each monostable having a predetermined switching time and being triggered by a negative pulse, that amplifier which delivers the signal V2 - V1 not being followed by a monostable, each monostable outputting to a two input AND gate whose second input is supplied by the signals Vi 1 - Vi , and each of the (N - 2) AND gates outputting to an (N - 2) OR gate which delivers a signal if the frequency fM is in the band fo -f''o.
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) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |