US3900847A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Satellite aided vehicle avoidance system
Assignee: National Aeronautics and Space Administration
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Filing: 1972-01-21
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Granted: 1975-08-19
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Expires: 1992-01-21
Abstract
Abstract An improved satellite aided vehicle avoidance system (SAVAS) is described in which exact range from a protected vehicle to an intruding vehicle with mutual-collision heading and velocity is derived without signal transmission by the protected vehicle or use of synchronized time reference devices. The improved SAVAS enables the practicing of a novel method which comprises the steps of: broadcasting a repeated signal sequence from a satellite to participating vehicles; transponding portions of the sequence in turn by the vehicles with an additional signal; receiving in the protected vehicle the direct satellite signal, the transponded satellite signal and the additional signal; measuring in the protected vehicle the propagation delay between the received direct and transponded satellite signals, the Doppler frequency difference between the received direct and transponded satellite signals, and the Doppler shift of the received additional signal; and determining the range between the protected vehicle and the intruding vehicle which transponded the satellite signal and added the additional signal by multiplying the propagation delay by the velocity of light and further by the ratio of the obtained Doppler shift of the additional signal to the obtained Doppler difference between the direct and transponded satellite signals. Additional steps of measuring time-to-collision from the delay and Doppler measurements, establishing ordered time-slots from the form of the satellite signal may be included.
Inventors
- 👤 Ernest R Steele
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:08
CPC Classifications
G; G01; G01S; G01S11/00; G01S11/02; G01S11/10
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
187 words
A method of measuring range from a protected vehicle to an intruding vehicle with the aid of a signal transmitted by a satellite to a population of vehicles comprising the steps of: receiving in each of the vehicles the satellite transmitted signal; transponding the satellite transmitted signal by said intruding vehicle; receiving the transponded signal in said protected vehicle; utilizing in said protected vehicle the satellite transmitted signal, directly received by said protected vehicle, and the satellite transmitted signal transponded by said intruding vehicle, to derive a propagation delay of the transponded satellite signal relative to the directly received satellite signal and a Doppler difference between the directly received satellite signal frequency and the transponded satellite signal frequency; transmitting by said intruding vehicle an additional signal; receiving said additional signal in said protected vehicle; measuring in said protected vehicle the Dopper shift of said additional signal; and deriving in said protected vehicle the range from said protected vehicle to said intruding vehicle as the product of the said propagation delay, the speed of lignt, and the ratio of the said Doppler shift to the said Doppler difference.
Claim 2
Independent Claim
187 words
A method of measuring range from a protected vehicle to an intruding vehicle with the aid of a signal transmitted by a satellite to a population of vehicles comprising the steps of: receiving in each of the vehicles the satellite transmitted signal; transponding the satellite transmitted signal by said intruding vehicle; receiving the transponded signal in said protected vehicle; utilizing in said protected vehicle the satellite transmitted signal, directly received by said protected vehicle, and the satellite transmitted signal transponded by said intruding vehicle, to derive a propagation delay of the transponded satellite signal relative to the directly received satellite signal and a Doppler difference between the directly received satellite signal frequency and the transponded satellite signal frequency; transmitting by said intruding vehicle an additional signal; receiving said additional signal in said protected vehicle; measuring in said protected vehicle the Dopper shift of said additional signal; and deriving in said protected vehicle the range from said protected vehicle to said intruding vehicle as the product of the said propagation delay, the speed of lignt, and the ratio of the said Doppler shift to the said Doppler difference.
Claim 3
Dependent Claim
40 words
The method as recited in claim 1 wherein said protected vehicle transponds the satellite signals received thereby and transmits an additional signal for use by another of said population of vehicles in computing the range of said protected vehicle therefrom.
Claim 4
Dependent Claim
23 words
The method as recited in claim 2 wherein the vehicles transpoNding said satellite signals transmit therewith coded information pertaining to said transponding vehicles.
Claim 5
Dependent Claim
27 words
The method as recited in claim 3 wherein said coded information is one of the group of information consisting of vehicle altitude, vehicle identity and vehicle maneuver.
Claim 6
Dependent Claim
41 words
The method as recited in claim 1 further including the step of computing the time-to-collision between said protected vehicle and said intruding vehicle as a function of said propagation delay, the frequency of the satellite transmitted signals and said Doppler difference.
Claim 7
Independent Claim
215 words
A system for measuring range between a protected vehicle and an intruding vehicle, both vehicles being part of a vehicle population to which signals are transmitted from an earth-orbiting satellite, the system comprising: first and second receiving means in said protected and intruding vehicles respectively for receiving therein the signals transmitted by said satellite; transponding means in said intruding vehicle for transponding the satellite signals received by said second receiving means; third receiving means in said protected vehicle for receiving the transponded satellite signals transponded in said intruding vehicle; transmitting means in said intruding vehicle for transmitting an added signal; fourth receiving means in said protected vehicle for receiving said added signal; and computing means including means for deriving a relative propagation delay, designated as T, which is the difference in the times of reception of said satellite signals by said first receiving means and of said transponded satellite signals by said third receiving means, means for deriving a Doppler difference, designated as DR, which is the difference in the frequencies of the signals received by said first and third receiving means, means for deriving a Doppler shift, designated as DT, of the frequency of the received added signal, and means for computing the range, designated as R, between said protected and intruding vehicle, where
Claim 8
Independent Claim
215 words
A system for measuring range between a protected vehicle and an intruding vehicle, both vehicles being part of a vehicle population to which signals are transmitted from an earth-orbiting satellite, the system comprising: first and second receiving means in said protected and intruding vehicles respectively for receiving therein the signals transmitted by said satellite; transponding means in said intruding vehicle for transponding the satellite signals received by said second receiving means; third receiving means in said protected vehicle for receiving the transponded satellite signals transponded in said intruding vehicle; transmitting means in said intruding vehicle for transmitting an added signal; fourth receiving means in said protected vehicle for receiving said added signal; and computing means including means for deriving a relative propagation delay, designated as T, which is the difference in the times of reception of said satellite signals by said first receiving means and of said transponded satellite signals by said third receiving means, means for deriving a Doppler difference, designated as DR, which is the difference in the frequencies of the signals received by said first and third receiving means, means for deriving a Doppler shift, designated as DT, of the frequency of the received added signal, and means for computing the range, designated as R, between said protected and intruding vehicle, where
Claim 9
Dependent Claim
28 words
The arrangement as recited in claim 6 further including means in said protected vehicle for transponding the satellite signal received therein and means for transmitting an added signal.
Claim 10
Dependent Claim
31 words
The arrangement as recited in claim 7 further including means in each vehicle for transmitting coded information pertaining to said vehicle with the transponded vehicle signals or with the added signal.
Claim 11
Dependent Claim
31 words
The arrangement as recited in claim 8 wherein means in each vehicle for transmitting coded information comprise means for transmitting information related to either vehicle altitude, vehicle identity or vehicle maneuver.
Claim 12
Dependent Claim
45 words
The arrangement as recited in claim 6 further including means in said protected vehicle for computing a time-to-collision between the protected and intruding vehicles as a function of T, f and DR, where f is the frequency of the satellite signal, time-to-collision being equal to
Claim 13
Independent Claim
245 words
A method of assessing a threat of collision by determining the range between two vehicles on mutual collision courses comprising the steps of: transmitting signals from a satellite to said vehicles; receiving said signals by each of said vehicles; coherently transponding said signals by each of said vehicles; receiving the transponded signals from one vehicle by the second vehicle; measuring the Doppler difference between the direct satellite signal frequency and the transponded satellite signal frequency from the said one vehicle by the said second vehicle; measuring the propagation delay of thE said received transponded signal relative to the said received direct signal at the said second vehicle; transmitting an additional signal at a known frequency by each of said vehicles; receiving the said additional signal by the said second vehicle; measuring the Doppler shift in the received additional signal by the said second vehicle; adjusting the said Doppler shift in the received additional signal frequency by multiplying the said shift by the ratio of the said satellite signal frequency to the said additional signal frequency when the said frequencies differ sufficiently to cause unacceptable error; and finally multiplying the said measured propagation delay by the velocity of light and further multiplying by the ratio of the said adjusted Doppler shift in the received additional signal to the said Doppler difference between the said received direct satellite signal and the said received transponded satellite signal to obtain a measurement of range between the said two vehicles.
Claim 14
Independent Claim
245 words
A method of assessing a threat of collision by determining the range between two vehicles on mutual collision courses comprising the steps of: transmitting signals from a satellite to said vehicles; receiving said signals by each of said vehicles; coherently transponding said signals by each of said vehicles; receiving the transponded signals from one vehicle by the second vehicle; measuring the Doppler difference between the direct satellite signal frequency and the transponded satellite signal frequency from the said one vehicle by the said second vehicle; measuring the propagation delay of thE said received transponded signal relative to the said received direct signal at the said second vehicle; transmitting an additional signal at a known frequency by each of said vehicles; receiving the said additional signal by the said second vehicle; measuring the Doppler shift in the received additional signal by the said second vehicle; adjusting the said Doppler shift in the received additional signal frequency by multiplying the said shift by the ratio of the said satellite signal frequency to the said additional signal frequency when the said frequencies differ sufficiently to cause unacceptable error; and finally multiplying the said measured propagation delay by the velocity of light and further multiplying by the ratio of the said adjusted Doppler shift in the received additional signal to the said Doppler difference between the said received direct satellite signal and the said received transponded satellite signal to obtain a measurement of range between the said two vehicles.
Claim 15
Dependent Claim
30 words
A method of assessing a threat of collision as claimed in claim 11 including the additional step of encoding pertinent information onto the transponded satellite signal by a transponding vehicle.
Claim 16
Dependent Claim
31 words
A method of assessing a threat of collision as claimed in claim 11 including the additional step of encoding vehicle altitude information onto the transponded satellite signal by a transponding vehicle.
Claim 17
Dependent Claim
30 words
A method of assessing a threat of collision as claimed in claim 11 including the additional step of encoding vehicle identity onto the transponded satellite signal by a transponding vehicle.
Claim 18
Dependent Claim
31 words
A method of assessing a threat of collision as claimed in claim 11 including the additional step of encoding vehicle maneuver information onto the transponded satellite signal by a transponding vehicle.
Claim 19
Dependent Claim
60 words
A method of assessing a threat of collision as claimed in claim 11 including the additional step of obtaining a time-to-collision by multiplying the said propagation delay by the frequency of the said satellite signal and dividing by the said Doppler difference between the direct satellite signal frequency and the received transponded satellite signal frequency at the said second vehicle.
Claim 20
Dependent Claim
32 words
A method of assessing a thread of collision as claimed in claim 11 wherein the step of transmitting signals from a satellite comprises transmitting continuous wave signals with timing signals modulated thereon.
Claim 21
Dependent Claim
36 words
A method of assessing a threat of collision as claimed in claim 11 wherein the step of transmitting signals from a satellite comprises the step of transmitting interrupted continuous wave signals with timing signals modulated thereon.
Claim 22
Dependent Claim
38 words
A method of assessing a threat of collision as claimed in claim 17 wherein the step of transmitting signals from a satellite comprises the step of transmitting continuous wave signals with the timing signals being phased modulated thereon.
Claim 23
Dependent Claim
46 words
A method of assessing a threat of collision as claimed in claim 17 wherein the step of transmitting signals from a satellite comprises the step of transmitting interrupted continuous wave signals with timing signals which include an epoch-start signal followed by the time-slot-start signals modulated thereon.
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) | 1978-08-18 | 1979-02-17 | 1979-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-18 | 1983-02-17 | 1983-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-18 | 1987-02-17 | 1987-08-19 | $7700.00 | Window Closed / Lapsed |