US3555165A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Acoustic target simulator
Assignee: United States Department of the Navy
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Filing: 1969-01-29
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Granted: 1971-01-12
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Expires: 1989-01-29
Abstract
Abstract Apparatus for simulating acoustic echoes of sonar pulses from any selected target configuration including a hydrophone whose output signal is fed to a signal processor for modifying a received sonar pulse and generating an electrical echo analogue signal applied to a projector for transmission. The processor includes a modulator for down modulating the carrier frequency of the received pulse and delay devices for delaying the pulse by varying degrees equivalent to the travel times for the pulse between successive major echo producing discontinuities in the target whose echo is being simulated to form a series of pulses. The pulses are controlled in amplitude in accordance with the appropriate target strengths for the succession of discontinuities and are fed to fill-in and summing circuits for adding white noise of desired envelope characteristics in the intervals between successive pulses to form the echo analogue signal. A second modulator shifts the frequency band of the echo analogue signal upwardly and introduces a selected Doppler shift thereinto prior to its application to the projector for acoustic transmission. Feedback elimination circuitry delays and shifts the phase of the echo analogue signal and applies the resulting signal to a summer for eliminating the effect of acoustic feedback.
Inventors
- 👤 Kurt L Ettenhofer
- 👤 Francis E Huff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:20
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/52; G01S7/52004
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
93 words
A method of simulating the echo of a sonar pulse from an acoustic energy reflective target having reflection producing discontinuities positioned at different ranges along the path of the sonar pulse comprising the steps of: receiving the sonar pulse; delaying the sonar pulse received to provide at least one replica pulse displaced in time as a function of the difference in ranges of the discontinuities in the target along the pulse path; collecting the received pulse and the replica pulse to provide an echo analogue sIgnal; and acoustically projecting the echo analogue signal.
Claim 2
Independent Claim
93 words
A method of simulating the echo of a sonar pulse from an acoustic energy reflective target having reflection producing discontinuities positioned at different ranges along the path of the sonar pulse comprising the steps of: receiving the sonar pulse; delaying the sonar pulse received to provide at least one replica pulse displaced in time as a function of the difference in ranges of the discontinuities in the target along the pulse path; collecting the received pulse and the replica pulse to provide an echo analogue sIgnal; and acoustically projecting the echo analogue signal.
Claim 3
Dependent Claim
31 words
A method according to claim 1 further comprising the step of attenuating both the received pulse and the replica pulse in accordance with the relative target strengths of the corresponding discontinuities.
Claim 4
Dependent Claim
30 words
A method according to claim 2 further comprising the step of adding white noise to the echo analogue signal during the interval between the received pulse and the replica pulse.
Claim 5
Dependent Claim
48 words
A method according to claim 2 further comprising the steps of: generating a fill-in noise envelope during the interval between the received pulse and the replica pulse; amplitude modulating white noise with the fill-in noise envelope; and summing the amplitude modulated white noise with the echo analogue signal.
Claim 6
Dependent Claim
80 words
A method according to claim 2 further comprising the steps of: modulating the received pulse to provide a received pulse having a down-shifted frequency band; and modulating the echo analogue signal to provide for projection of an echo analogue signal having an up-shifted frequency band corresponding to the sum of that of the received pulse and a selected shift attributable to the Doppler effect wherein the simulated target appears to be moving relative to a source of the sonar pulse.
Claim 7
Dependent Claim
62 words
A method according to claim 2 further comprising the steps of; providing a delayed image of the echo analogue signal shifted 180* in phase with respect to the projected echo analogue signal being received during said step of projecting; and summing the image signal with the received signal to provide a received pulse unaffected by acoustical feedback during said step of projecting.
Claim 8
Dependent Claim
91 words
Apparatus for simulating the sonar signal echo from a target of predetermined configuration comprising: hydrophone means for receiving a sonar signal and providing an input signal; processing means connected to said hydrophone means for receiving said input signal and providing an echo analogue signal having said input signal and at least one replica signal displaced from each other in time as a function of the range difference in reflection producing discontinuities of the target; and projector means connected to said processing means for receiving and for projecting said echo analogue signal.
Claim 9
Dependent Claim
91 words
Apparatus for simulating the sonar signal echo from a target of predetermined configuration comprising: hydrophone means for receiving a sonar signal and providing an input signal; processing means connected to said hydrophone means for receiving said input signal and providing an echo analogue signal having said input signal and at least one replica signal displaced from each other in time as a function of the range difference in reflection producing discontinuities of the target; and projector means connected to said processing means for receiving and for projecting said echo analogue signal.
Claim 10
Dependent Claim
100 words
Apparatus according to claim 7 wherein said processing means comprises: delay means connected to receive said input signal for providing a plurality of replica signals successively displaced in time; a plurality of amplitude control means each connected for receiving a respective one of said input and said replica signals, said control means adjusting the relative amplitudes of said input and said replica signals in accordance with the relative target strengths of discontinuities in the target; and summing means connected to said amplitude control means for receiving and summing said input and said replica signals for providing said echo analogue signal.
Claim 11
Dependent Claim
49 words
Apparatus according to claim 8 wherein said processing means further comprises means connected to receive said electrical echo analogue signal for providing to said projector means said electrical analogue signal having amplitude controlled noise superimposed thereon during the intervals between successive ones of said input and said replica signals.
Claim 12
Dependent Claim
77 words
Apparatus according to claim 7 wherein said processing means further comprises: delay means connected for receiving said input signal and providing at least one replica signal delayed in time; a plurality of attenuator means each connected for receiving and attenuating a respective one of said input signal and said replica signal; and first summing means connected to said attenuator means for receiving and summing said input and said replica signals and for providing said echo analogue signal.
Claim 13
Dependent Claim
49 words
Apparatus according to claim 10 wherein said processing means further comprises superimposing means connected to receive said echo analogue signal for superimposing amplitude controlled noise on said echo analogue signal during the interval between said input and said replica signals and providing said analogue signal to said projector means.
Claim 14
Dependent Claim
63 words
Apparatus according to claim 11 wherein said superimposing means further comprises: fill-in circuit means receiving said echo analogue signal for providing amplitude modulated noise during the interval between said input and said replica signals; and second summing means connected to receive said echo analogue signal and said amplitude modulated noise for providing said echo analogue signal having superimposed noise to said projector means.
Claim 15
Dependent Claim
110 words
Apparatus according to claim 12 wherein said fill-in circuit means comprises: envelope detector means connected to said first summing means for receiving said echo analogue signal and providing a DC output signal indicative of the envelope of said echo analogue signal; decay means connected to receive said DC output signal for imposing an exponential decay of the trailing ends of pulses in said DC signal to provide a fill-in noise envelope signal; generator means providing a white noise signal; and modulator means connected to receive said white noise signal and said fill-in noise envelope signal for amplitude modulating said white noise signal and providing said amplitude modulated white noise signal.
Claim 16
Dependent Claim
62 words
Apparatus according to claim 13 wherein said fill-in circuit means further comprises: said modulator means being responsive to an inhibit signal for providing no output signal; and current direction sensing means interposed between said envelope detector and said decay means for providing said inhibit signal to said modulator during the occurrence of said input and replica signals in said echo analogue signal.
Claim 17
Dependent Claim
25 words
Apparatus according to claim 14 wherein said decay means comprises a resistor and a capacitor connected in parallel across the input of said modulator means.
Claim 18
Dependent Claim
61 words
Apparatus according to claim 15 wherein said fill-in circuit means further comprises: threshold detector means connected to receive the last occurring replica signal for providing in response thereto an inhibit signal; and OR gate means connected to receive said inhibit signals of said threshold detector means and said current direction sensor means for providing said inhibit signal to said modulator means.
Claim 19
Dependent Claim
112 words
Apparatus according to claim 10 wherein said processing means further comprises: oscillator means for providing an oscillator output signal having a first frequency; first modulator means connected to receive said oscillator output signal and being interposed between said hydrophone means and said delay means for providing said input signal having a down-shifted frequency band to said delay means; variable oscillator means for providing a variable oscillator output signal having a frequency equal to the sum of said first frequency and a Doppler shift frequency; and second modulator means interposed between said summing means and said projector means for providing said echo analogue signal having an up-shifted frequency band to said projector means.
Claim 20
Dependent Claim
48 words
Apparatus according to claim 17 wherein said processing means further comprises: a bypass switch interposed between said first modulator means and said delay means; and variable delay means connected to said bypass switch for imposing upon said input signal a time delay corresponding to a selected range difference.
Claim 21
Dependent Claim
66 words
Apparatus according to claim 18 wherein said processing means further comprises: relay means interposed between said hydrophone means and said delay means for normally transmitting said input signal to said delay means and being responsive to a control signal for interrupting said transmission; and threshold means connected to receive said echo analogue signal and being responsive thereto for providing said control signal to said relay means.
Claim 22
Dependent Claim
79 words
APparatus according to claim 10 wherein said signal processor further comprises: feedback elimination means connected to receive said echo analogue signal for providing a time delayed replica of said echo analogue signal shifted pi radians in phase; and second summing means connected to receive and sum said echo analogue replica signal and said input signal from said hydrophone for providing to said delay means said input signal substantially free of the component contributed by said projected echo analogue signal.
Claim 23
Dependent Claim
86 words
Apparatus according to claim 20 wherein said feedback elimination means comprises: second delay means connected to receive and delay said echo analogue signal a period of time which is a function of a separation distance between said hydrophone means and said projector means; phase shift means connected to said second delay means for imposing a phase shift of pi radians upon said delayed echo analogue signal; and attenuator means interconnecting said phase shift means and said second summing means for providing said echo analogue replica signal.
References Cited (Backward Citations)
US2881535A
Cited
US3008244A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-01-11 | 1974-07-13 | 1975-01-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-01-11 | 1978-07-13 | 1979-01-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-01-11 | 1982-07-13 | 1983-01-12 | $7700.00 | Window Closed / Lapsed |