SPREAD-SPECTRUM POSITION MONITORING SYSTEM

• US 3,714,573 A
• Filed: 05/06/1970
• Issued: 01/30/1973
• Est. Priority Date: 05/06/1970
• Status: Expired due to Term

• Current Assignee: Burton C. Grossman
• Original Assignee: Burton C. Grossman
• Inventors: Grossman, Burton C.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Birmiel, H. A.
• Application Number:
  US05/034,962
• Time in Patent Office: 1,000 Days
• Field of Search: 325/32,122,39,51,55,117,45,60 343/112R,112PT
• US Class Current: 342/387
• CPC Class Codes: G01S 3/46 using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

Disclosed are systems capable of monitoring the positions of vehicles even under the multipath transmission conditions as may exist in a city. In one such system each vehicle contains apparatus which, without being interrogated, repetitively transmits a uniquely coded spread-spectrum identification signal asynchronous to the repetitive identification signals transmitted by all other system vehicles. The signal from each vehicle is received at a plurality of antenna locations and supplied to a central station where it is pulse compressed by a matched filter set to provide information from which the identity of the vehicle can be determined. The received signals are additionally processed at the central station to determine relative differences in the time of arrival of the signals at each antenna in order to determine the vehicle'"'"''"'"'s position.

Claims

1. A position monitoring system in which a plurality of mobile transmitters transmit modulated spread-spectrum signals asynchronously and wherein said signals are received at a remote location for use in identifying and locating the transmitters and thereby monitoring their positions, said system comprising:

at least one mobile transmitter for transmitting spread-spectrum signals to a remote location for use in monitoring said transmitters'"'"''"'"' position, said transmitter comprising;

means for generating a modulating signal having a predetermined code unique to said transmitter for use in supplying information from said transmitter;

means responsive to said modulating signal for generating a modulated, spread-spectrum signal, said modulated signal having modulation components which are decodable for use in supplying information from and locating said transmitter; and

means for transmitting said modulated-spread spectrum signal asynchronously with respect to other transmitters in said system; and

signal receiving apparatus at said remote location for receiving a spread-spectrum signal, having unique decodable modulation components, from each of said transmitters, said receiving apparatus comprising;

a plurality of means, each at a different station and each for receiving the signals from said transmitters;

signal compression means responsive to the received signals for developing a coded signal representative of the decodable components of each of said received spread-spectrum signals, all signals received from the same transmitter having decodable components unique to that transmitter;

means responsive to the coded signals for generating timing signals, said timing signals being representative of the difference in the time of arrival, at pairs of said receiving stations, of the signal received from each transmitter; and

means responsive to the timing signals and the coded signals for processing said signals to determine the position of each transmitter and information supplied from each transmitter.

2. A position monitoring system in which a plurality of mobile transmitters transmit modulated spread-spectrum signals asynchronously and wherein said signals are received at a remote location for use in identifying and locating the transmitters and thereby monitoring their positions, said system comprising:

at least one mobile transmitter for transmitting spread-spectrum signals to a remote location for use in monitoring said transmitters'"'"''"'"' position, said transmitter comprising;

means for generating a modulating signal having first and second portions whose time spacing comprises a code unique to said transmitter for use in identifying said transmitter;

means for generating a carrier signal of prescribed frequency;

means responsive to said modulating signal and said carrier signal for generating a modulated, spread-spectrum signal, said modulated signal having modulation components which are decodable for use in identifying and locating the transmitter; and

means for transmitting said modulated spread-spectrum signal asynchronously with respect to other transmitters in said system; and

signal receiving apparatus at said remote location for receiving a spread-spectrum signal, having unique decodable modulation components, from each of said transmitters, said receiving apparatus comprising;

a plurality of means, each at a different station and each for receiving the signals from said transmitters;

signal compression means responsive to the received signals from each transmitter for developing coded signals representative of the decodable components of said received spread-spectrum signals, at least one of the coded signals having first and second portions whose time spacing corresponds to the spacing between said transmitted first and second portions, all signals received from the same transmitter having a spacing between portions unique to that transmitter;

recognition means responsive to the first and second portions of said coded signals for generating signals for use in identifying the transmitters associated with the respective coded signals;

means responsive to the coded signals for generating timing signals, said timing signals being representative of the difference in the time of arrival, at pairs of said receiving stations, of the signal received from each transmitter; and

means responsive to the timing signals and the identifying signals for processing said signals to determine the position and identity of each transmitter.

3. A position monitoring system in which a plurality of mobile transmitters transmit modulated spread-spectrum signals asynchronously and wherein said signals are received at a remote location for use in identifying and locating the transmitters and Thereby monitoring their positions, said system comprising:

at least one mobile transmitter for transmitting spread-spectrum signals to a remote location for use in monitoring said transmitters'"'"''"'"' position, said transmitter comprising;

means for generating a modulating signal having a first selected sequence of pulses and a second selected sequence of pulses, said second pulse sequence commencing a predetermined time unique to said transmitter after the commencement of said first pulse sequence for use in identifying said transmitter;

means for generating a carrier signal of prescribed frequency;

a phase modulator responsive to the carrier signal and the leading and trailing edges of each of the pulses in said first and second sequences for generating a phase-modulated, spread-spectrum signal whose phase changes a prescribed amount in response to each of said pulse edges, said modulated signal having modulation components which are decodable for use in identifying and locating the transmitter; and

means for transmitting said phase modulated spread-spectrum signal asynchronously with respect to other transmitters in said system; and

signal receiving apparatus at said remote location for receiving a phase-modulated spread-spectrum signal, having unique decodable modulation components, from each of said transmitters, said receiving apparatus comprising;

a plurality of antennas and corresponding antenna receivers, each at a different station and each for receiving the signals from said transmitters;

pulse compression means comprising a matched filter set associated with each of said antennas for developing pulse-type coded signals representative of the decodable components of each of the phase modulated spread-spectrum signals received from each transmitter, at least one of the signals having a pair of first and second pulses whose time spacing corresponds to the spacing between said transmitted first and second pulse sequences, all signals received from the same transmitter having a spacing between pulses in said pulse pair unique to that transmitter;

recognition means responsive to the pulse pair of each coded signal for generating signals for use in identifying the transmitter associated with the respective coded signals;

means responsive to the coded signals for generating timing signals, said timing signals being representative of the difference in the time of arrival, at pairs of said antennas of the signal received from each transmitter; and

means responsive to the timing signals and the identifying signals for processing said signals to determine the position and identity of each transmitter.

4. A system in accordance with claim 3 wherein said phase modulator comprises a bi-phase modulator for generating a phase-modulated signal whose phase changes substantially 180* in response to each of said pulse edges.

5. A system in accordance with claim 3 wherein said phase modulator comprises a quadri-phase modulator for generating a phase-modulated signal whose phase changes substantially in increments of 90* in response to each of said pulse edges.

6. A position monitoring system in which a plurality of mobile transmitters transmit modulated spread-spectrum signals asynchronously and wherein said signals are received at a remote location for use in identifying and locating the transmitters and thereby monitoring their positions, said system comprising:

at least one mobile transmitter for transmitting spread-spectrum signals to a remote location for use in monitoring said transmitters'"'"''"'"' position, said transmitter comprising;

means for generating a modulating signal having a first selected binary-coded sequence of pulses and a second selected binary-coded sequence of pulses, said second pulse sequence commencing a predetermined time unique to said transmitter after the commencement of said first pulse sequence for use in identifying said transmitter;

means for generating a carrier signal of prescribed frequency;

a phase modulator responsive to the carrier signal and the leading and trailing edges of each of the pulses in said first and second sequences for generating a phase-modulated, spread-spectrum signal whose phase changes a prescribed amount in response to each of said pulse edges, said modulated signal having modulation components which are decodable for use in identifying and locating the transmitter; and

means for transmitting said phase-modulated spread-spectrum signal asynchronously with respect to other transmitters in said system; and

signal receiving apparatus at said remote location for receiving a phase-modulated, spread-spectrum signal, having unique decodable modulation components, from each of said transmitters, said receiving apparatus comprising;

antenna means including first, second, and third fixed antennas and corresponding antenna receivers each at a different station and each for receiving the signals from said transmitters;

pulse compression means, including first, second, and third sets of matched filters responsive to signals received from said first, second, and third fixed antennas, respectively, and each set of filters being matched to the decodable components in the transmitted signals received at each corresponding antenna, for respectively developing first, second, and third coded signals, at least one of which comprises a pair of pulses whose time spacing corresponds to the spacing between said first and second transmitted pulse sequences, all signals received from the same transmitter having a spacing between pulses in said pulse pair unique to that transmitter;

recognition means responsive to the time spacing between the pulses in said pulse pairs for generating signals for use in identifying the respective transmitters;

a plurality of time interval measurement devices, each responsive to a selected pair of first, second, and third coded signals, for generating a corresponding plurality of timing signals, said timing signals being representative of the difference in the time of arrival at pairs of said fixed antennas of the signal received from each transmitter; and

means responsive to the timing and identification signals for processing said signals to determine the position and identity of each of said transmitters.

7. A transmitter usable in a position monitoring system wherein a plurality of mobile transmitters asynchronously transmit spread-spectrum signals to a remote station for use in monitoring their positions, said transmitter comprising:

means for generating a modulating signal having a predetermined code unique to said transmitter for use in supplying information from said transmitter;

means responsive to said modulating signal for generating a modulated, spread-spectrum signal, said modulated signal having modulation components which are decodable for use in supplying information from and locating the transmitter; and

means for transmitting said modulated, spread-spectrum signal asynchronously with respect to other transmitters in said system.

8. A transmitter as described in claim 7 wherein said means for generating a modulating signal generates a pulse-type sequence which comprises a code unique to said transmitter for use in identifying said transmitter.

9. A transmitter usable in a position monitoring system wherein a plurality of mobile transmitters asynchronously transmit spread-spectrum signals to a remote station for use in monitoring their positions, said transmitter comprising:

means for generating a modulating signal having first and second portions whose time spacing comprises a code unique to said transmitter for use in identifying said transmitter;

means for generating a carrier signal of prescribed frequency;

means responsive to said modulating signal and said carrier signal for generating a modulated, spread-spectrum signal, said modulated signal having modulation components which are decodable for use in identifying and locating the transmitter; and

means for transmitting said modulated, spread-spectrum signal asynchronously with respect to other transmitters in said system.

10. A transmitter as described in claim 9, wherein said modulating signal generating means, generates a modulating signal having a first selected sequence of pulses and a second selected sequence of pulses, said second pulse sequence commencing a predetermined time unique to said transmitter after the commencement of said first pulse sequence for use in identifying said transmitter;

and wherein said spread-spectrum signal generating means is responsive to the leading and trailing edges of each pulse in both said sequences for generating a phase-modulated, spread-spectrum signal whose phase changes a prescribed amount in response to each of said pulse edges.

11. A transmitter as described in claim 10 wherein said spread-spectrum signal generating means comprises a bi-phase modulator for generating a phase-modulated signal whose phase changes substantially 180* in response to each of said pulse edges.

12. A transmitter as described in claim 10 wherein said spread-spectrum signal generating means comprises a quadriphase modulator for generating a phase-modulated signal whose phase changes substantially in increments of 90* in response to each of said pulse edges.

13. Signal receiving apparatus usable in a position monitoring system wherein a predetermined modulated spread-spectrum signal, having unique decodable components is received from each of a plurality of mobile transmitters for use in identifying and locating said transmitters, which transmit asynchronously with respect to one another, said signal receiving apparatus comprising:

a plurality of means, each at a different station, and each for receiving the signals from said transmitters;

signal compression means responsive to the received signals for developing a coded signal representative of the decodable components of each of said received spread-spectrum signals, all signals received from the same transmitter having decodable components unique to that transmitter;

timing means responsive to the coded signals for generating timing signals, said timing signals being representative of the difference in the time of arrival, at pairs of said receiving stations, of the signal received from each transmitter; and

processing means responsive to the timing signals and the coded signals for processing said signals to determine the position and identity of each transmitter.

14. Signal receiving apparatus usable in a position monitoring system wherein a predetermined modulated spread-spectrum signal, having decodable components representative of first and second portions whose time spacing comprises a unique code, is received from each of a plurality of mobile transmitters for use in identifying and locating said transmitters which transmit asynchronously with respect to one another, said signal receiving apparatus comprising:

a plurality of antennas and corresponding antenna receivers, each at a different station and each for receiving the signals from said transmitters;

signal compression means responsive to the received signals from each transmitter for developing coded signals representative of the decodable components of each of said received spread-spectrum signals at least one of the coded signals having first and second portions whose time spacing corresponds to the spacing between said transmitted first and second portions, all signals received from the same transmitter having a spacing between portions unique to that transmitter;

recognition means responsive to the first and second portions of said coded signals for generating signals for use in identifying the transmitters associated with the respective coded signals;

means responsive to the coded signals for generating timing signals, said timing signals being representative of the difference in the time of arrival, at pairs of said aNtennas, of the signal received from each transmitter; and

means responsive to the timing signals and the identifying signals for processing said signals to determine the position and identity of each transmitter.

15. Signal receiving apparatus usable in a position monitoring system wherein a predetermined phase-modulated, spread-spectrum signal having decodable components representative of first and second pulse sequences whose time spacing comprises a unique code, is received from each of a plurality of mobile transmitters for use in identifying and locating said transmitters which transmit asynchronously with respect to one another, said signal receiving apparatus comprising:

a plurality of antennas and corresponding antenna receivers, each at a different station and each for receiving the signals from said transmitters;

pulse compression means comprising a matched filter set associated with each of said antennas for developing pulse-type coded signals representative of the decodable components of each of the phase-modulated, spread-spectrum signals, received from each transmitter at least one of the coded signals having a pair of first and second pulses whose time spacing corresponds to the spacing between said transmitted first and second pulse sequences, all signals received from the same transmitter having a spacing between pulses in said pulse pair unique to that transmitter;

recognition means responsive to the pulse pair in said coded signal for generating signals for use in identifying the transmitter associated with the respective coded signals;

means responsive to the coded signals for generating timing signals, said timing signals being representative of the difference in the time of arrival, at pairs of said antennas, of the signal received from each transmitter; and

means responsive to the timing signals and the identifying signals for processing said signals to determine the position and identity of each transmitter.

16. A receiver as described in claim 15 wherein said signal compression means comprises a first matched filter associated with each of said antenna means, said matched filter being adapted to develop a first pulse representative of the decodable component due to said first transmitted pulse sequence and wherein at least one of said antennas has associated therewith a second matched filter adapted to develop a second pulse representative of the decodable component due to said second transmitted pulse sequence.