US 4,359,733 A · Satellite-based vehicle position determining system

Abstract

A system for determining the positions of a plurality of vehicles traveling on or above a defined sector of the earth's surface comprises a transponder carried by each vehicle for transmitting a uniquely coded beacon signal in response to a general interrogation signal, at least three repeater-carrying satellites at spaced orbital locations above the earth for receiving and retransmitting the beacon signals produced by the vehicles, and a ground station for periodically transmitting the general interrogation signal and for receiving and processing the beacon signals retransmitted by the three satellites in order to determine vehicle position. In order to avoid signal overlap and equipment saturation at the ground station, each vehicle transponder includes means responsive to the general interrogation signal for inhibiting the transmission of further beacon signals by the transponder for a predetermined time interval following the response of the transponder to the general interrogation signal. In a preferred embodiment of the invention, the inhibited interval of the vehicle transponders may be varied automatically in response to a command signal transmitted by the ground station.

Claims49

Dependent claims

A system for determining the positions of a plurality of vehicles traveling on or above a defined sector of the earth's surface, comprising:

(a) a transponder carried by each one of said vehicles for transmitting, in response to a general interrogation signal directed to said plurality of vehicles, a beacon signal coded with information uniquely identifying said one vehicle, said transponder including means reponsive to said general interrogation signal for inhibiting the transmission of further beacon signals by said transponder for a predetermined time interval following the response of said transponder to said general interrogation signal;
(b) three satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the beacon signals transmitted by said vehicle transponders, said three satellites thereby collectively producing three retransmitted beacon signals for each beacon signal produced by each one of said vehicle transponders;
and
(c) a ground station for periodically transmitting said general interrogation signal and for receiving and processing said retransmitted beacon signals, said ground station including:
(1) means for detecting the arrival time of each retransmitted beacon signal at the ground station;
(2) means for detecting the vehicle identifying information carried by each retransmitted beacon signal;
and
(3) means for calculating the instantaneous position of each one of said vehicles within said sector based upon the time of transmission of the interrogation signal from the ground station and the arrival times of the three retransmitted beacon signals which carry vehicle identifying information identifying said one vehicle.

5 more elements

A method for determining the positions of a plurality of vehicles traveling on or above a defined sector of the earth's surface using three satellites at spaced orbital locations above the earth, each one of said vehicles carrying a transponder for transmitting, in response to a general interrogation signal directed to said plurality of vehicles, a beacon signal coded with information uniquely identifying said one vehicle, said method comprising the steps of:

(a) transmitting a general interrogation signal from a ground station to said plurality of vehicles in order to give rise to the transmission of beacon signals by said vehicle-carried transponders;
(b) inhibiting the transmission of further beacon signals by each of said vehicle-carried transponders for a predetermined time interval following the response of said transponder to the general interrogation signal;
(c) receiving said beacon signals at said three satellites and retransmitting said received beacon signals to the ground station from said three satellites, whereby three retransmitted beacon signals are produced by said satellites for each beacon signal produced by each of said vehicle transponders;
(d) receiving each of said retransmitted beacon signals at the ground station and detecting its arrival time;
(e) detecting the vehicle identifying information carried by each retransmitted beacon signal;
and
(f) calculating the instantaneous position of each one of said vehicles within said sector based upon the time of transmission of the interrogation signal from the ground station and the arrival times of the three retransmitted beacon signals which carry vehicle identifying information identifying said one vehicle.

4 more elements

Dependencies are inferred from the claim text.

Satellite-based vehicle position determining system

Life of this patent

Satellite-based vehicle position determining system

Life of this patent

Abstract

Claims49