Patent US3795893A successfully refreshed from Google Patents.
US3795893A
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Doppler speed log
Assignee: Litton Marine Systems Inc
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Filing: 1971-07-06
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Granted: 1974-03-05
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Expires: 1991-07-06
Abstract
Abstract A doppler speed log for marine vessels transmits fore and aft pulses of high frequency sonic energy. The log normally operates in a mode such that a gating pulse permits signal processing circuits to respond only to signals derived from reflections from minute scatterers in the water occurring at a specified distance from the hull of the vessel. If the vessel is in shallow water, a variable threshold comparator permits the signal processing circuits to respond to reflections from the sea bottom when the magnitude of these reflected signals exceeds the threshold level. The processing circuit forms fore and aft enabling pulses each having a duration equal to the time required for the reception of a specified number of cycles of sonic energy reflected from the fore and aft directions, respectively. Pulses from a calibrated clock source are applied to an up-down counter during the time that only one of the enabling pulses exists. The readings corresponding to a specified number of transmitted pulses are accumulated and displayed on a suitable readout means.
Inventors
- 👤 J Kritz
- 👤 S Lerner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:21
CPC Classifications
G; G01; G01S; G01S15/00; G01S15/02; G01S15/50; G01S15/58; G01S15/60; Y; Y10; Y10S; Y10S367/00; Y10S367/90; Y10S367/902
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
167 words
A doppler speed log for a marine vessel comprising fore and aft downwardly-looking transducers, means to form periodic transmitting pulses, means for electrically exciting said transducers in response to said transmitting pulses so as to launch bursts of oscillatory sonic energy, said transducers being further constructed and arranged to produce electrical signals in response to reflected portions of said bursts of sonic energy, individual fore and aft channels for processing the respEctive fore and aft electrical signals, each of said processing channels including means for initiating a time gate, and means for terminating the time gate after the reception of a prescribed large number of oscillatory excursions of the received signal whereby the duration of said time gate is representative of the average period of the received oscillatory energy, said speed log further including means for determining the difference in duration of the respective time gates, and speed indicating means for displaying an indication of speed corresponding to said difference in the durations of said time gates.
Claim 2
Dependent Claim
167 words
A doppler speed log for a marine vessel comprising fore and aft downwardly-looking transducers, means to form periodic transmitting pulses, means for electrically exciting said transducers in response to said transmitting pulses so as to launch bursts of oscillatory sonic energy, said transducers being further constructed and arranged to produce electrical signals in response to reflected portions of said bursts of sonic energy, individual fore and aft channels for processing the respEctive fore and aft electrical signals, each of said processing channels including means for initiating a time gate, and means for terminating the time gate after the reception of a prescribed large number of oscillatory excursions of the received signal whereby the duration of said time gate is representative of the average period of the received oscillatory energy, said speed log further including means for determining the difference in duration of the respective time gates, and speed indicating means for displaying an indication of speed corresponding to said difference in the durations of said time gates.
Claim 3
Dependent Claim
60 words
The speed log of claim 1 wherein the means to initiate the time gate includes means to initiate such time gate at a prescribed time after the termination of a transmitting pulse, said prescribed time being equal to the time required for reflected energy to be returned to the transducer from a specified distance from the hull of the vessel.
Claim 4
Dependent Claim
33 words
The speed log of claim 1 further including means for accumulating the results of successive difference determinations, and distance indicating means responsive to said accumulation for displaying the distance travelled by said vessel.
Claim 5
Dependent Claim
114 words
The speed log of claim 3 wherein the means for initiating a time gate includes time responsive means for opening the channel to the reception of said electrical signals and means to maintain the channel in an open condition until the termination of a time gate, and wherein the means to determine the difference in duration of the respective time gates includes means in each channel to produce a direct enabling pulse during the time that the channel is in an open condition and means to produce a time difference signal during the occurrence of an enabling pulse in only one of said channels, said indicating means being responsive to said time difference signals.
Claim 6
Dependent Claim
129 words
The speed log of claim 4 wherein the means to maintain a channel in the open condition includes a flip-flop connected to produce a direct enabling signal while the channel is open and a complementary enabling signal while the channel is not open, and wherein said means for producing time difference signals includes an AND gate in each channel connected to receive a direct enabling signal from the flip-flop in the corresponding channel and a complementary enabling signal from the flip-flop in the opposite channel, said means for providing readout indications further including a source of clock pulses, each of said AND gates being connected to pass said clock pulses in response to simultaneous direct and complementary enabling pulses from the flip-flops in said corresponding and opposite channels respectively.
Claim 7
Dependent Claim
78 words
The speed log of claim 5 wherein the means to provide readout indications further includes an up-down counter connected to count in a first direction in response to time difference signals from one of said AND gates and in the opposite direction in response to time difference signals from the other of said AND gates, said readout indication means including speed indication means to accumulate the change in counter readings resulting from a predetermined number of transmission pulses.
Claim 8
Dependent Claim
53 words
The speed log of claim 6 wherein the clock source produces pulses at a repetition rate that is high with respect to the repetition rate of said transmit pulses, said speed log being further characterized in that said counter is coupled to each of said AND gates through an individual pulse rate divider.
Claim 9
Dependent Claim
42 words
The speed log of claim 7 wherein the repetition rate of the clock source is responsive to an external voltage, said speed log further including a water temperature sensing element and drive means to provide an external voltage to said clock source.
Claim 10
Dependent Claim
108 words
The speed log of claim 4 wherein the time responsive means includes means to produce a gating pulse after the lapse of a specified time interval following the termination of a transmit pulse, and gating means in each channel responsive to said gating pulses for passinG electrical signals applied to that channel after the occurrence of a gating pulse, and wherein said means to maintain the channel in an open condition includes overflow counter means responsive to electrical signals passed by said gating means, said counter means being connected to close said gating means after the counter has accepted a predetermined number of cycles of said electrical signal.
Claim 11
Dependent Claim
166 words
The speed log of claim 9 wherein each of said fore and aft channels includes a first sub-channel for forming fore and aft return signals respectively and a second sub-channel for forming fore and aft bottom return pulses respectively and wherein said time responsive means further includes a variable gain preamplifier in each channel for coupling electrical signals from a transducer to the corresponding sub-channels, variable threshold comparator means in each of said second sub-channels for forming bottom return pulses whenever a signal coupled from the corresponding preamplifier exceeds the instantaneous threshold established from the comparator, said time responsive means further including means to increase the gain of both preamplifiers linearly during the time interval between the termination of a transmit pulse and the following gating pulse, said time responsive means still further including means to decrease the threshold of said comparator exponentially during the same time interval and means to open said gating means in the corresponding channel in response to a bottom return pulse.
Claim 12
Dependent Claim
46 words
The speed log of claim 10 wherein the time responsive means further includes means to set the gain of both preamplifiers at the maximum level throughout a second time interval extending between the occurrence of a gating pulse and the initiation of the next transmit pulse.
Claim 13
Dependent Claim
152 words
The speed log of claim 11 wherein the means to form periodic transmitting pulses is a pulse repetition frequency oscillator, said oscillator containing a main capacitor and a constant current source connected thereacross so that said capacitor can be charged linearly with respect to time, a transmit pulse comparator connected to said capacitor and biased to a reference voltage whereby said comparator produces an output voltage whenever the capacitor voltage exceeds said reference voltage, a monostable multivibrator coupled to said comparator so that said multivibrator is triggered into its quasi-stable state in response to an output voltage from said comparator, said multivibrator being adjusted to have a quasi-stable state duration equal to the desired duration of a transmit pulse and being constructed to provide a transmit pulse during the time that the multivibrator is in said quasi-stable state, and switching means for shorting said capacitor throughout the occurrence of a transmit pulse.
Claim 14
Dependent Claim
95 words
The speed log of claim 12 wherein said means to produce gating pulses includes a gating pulse comparator in said oscillator, said gating pulse comparator being biased to a reference voltage of lower magnitude than said transmit pulse comparator, said gating pulse comparator being responsive to the voltage across said capacitor, whereby said gating pulse comparator produces an output signal at a predetermined time intermediate two successive transmit pulses, said means to produce a gating pulse further including a differentiating circuit to convert the output voltage of said gating pulse comparator into short duration pulses.
Claim 15
Dependent Claim
46 words
The speed log of claim 13 wherein the means for exponentially decreasing the threshold of the threshold comparator includes a parallel R-C network in said oscillator and switching means for connecting said R-C network across a source of voltage during the occurrence of a transmit pulse.
Claim 16
Dependent Claim
73 words
The speed log of claim 14 wherein the gain of said variable gain preamplifiers is responsive to a gain control voltage applied thereto, said oscillator including means to couple a voltage from said main capacitor to said preamplifiers until the occurrence of a gating pulse, said oscillator Further including means to couple a voltage indicative of the output of said gating pulse comparator to said preamplifiers after the occurrence of a gating pulse.
Claim 17
Dependent Claim
178 words
A doppler speed log for a marine vessel comprising fore and aft downwardly-looking transducers, means to form periodic transmitting pulses, means for electrically exciting said transducers in response to said transmitting pulses so as to launch bursts of oscillatory sonic energy, said transducers being further constructed and arranged to produce electrical signals in response to reflected portions of said bursts of sonic energy, individual fore and aft channels for processing the respective fore and aft electrical signals, each of said processing channels including time responsive means for opening the channel to the reception of said electrical signals, means to maintain said channel in an open condition for the reception of a specified number of oscillations of the electrical signal in that channel and means to produce an enabling pulse during the time that the channel is in the open condition, said speed log further including means for producing time difference signals during the occurrence of an enabling pulse in only one of said channels, and means to provide readout indications of the duration of said time difference signals.
Claim 18
Dependent Claim
178 words
A doppler speed log for a marine vessel comprising fore and aft downwardly-looking transducers, means to form periodic transmitting pulses, means for electrically exciting said transducers in response to said transmitting pulses so as to launch bursts of oscillatory sonic energy, said transducers being further constructed and arranged to produce electrical signals in response to reflected portions of said bursts of sonic energy, individual fore and aft channels for processing the respective fore and aft electrical signals, each of said processing channels including time responsive means for opening the channel to the reception of said electrical signals, means to maintain said channel in an open condition for the reception of a specified number of oscillations of the electrical signal in that channel and means to produce an enabling pulse during the time that the channel is in the open condition, said speed log further including means for producing time difference signals during the occurrence of an enabling pulse in only one of said channels, and means to provide readout indications of the duration of said time difference signals.
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) | 1977-03-04 | 1977-09-03 | 1978-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-04 | 1981-09-03 | 1982-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-04 | 1985-09-03 | 1986-03-05 | $7700.00 | Window Closed / Lapsed |