GPS pseudolite and receiver system using high anti-jam pseudolite signal structure

• US 6,031,487 A
• Filed: 03/25/1998
• Issued: 02/29/2000
• Est. Priority Date: 03/25/1998
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Rtx Corporation)
• Original Assignee: Rockwell Collins, Inc. (Rtx Corporation)
• Inventors: Mickelson, Wilmer A.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/047,566
• Time in Patent Office: 706 Days
• Field of Search: 342/18, 342/357.06, 342/357.12, 342/16, 701/213
• US Class Current: 342/357.48
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/215 issues related to spoofing
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

Disclosed is a GPS pseudolite transmitter, receiver and navigation system. The GPS pseudolite transmitter is adapted to transmit a first phase modulated L-band signal at a first signal pulse repetition rate having an associated first period time duration. The first phase modulated L-band signal is modulated with a short period code having a code epoch of at least about one millisecond. For each consecutive transmission pulse having the first period time duration, the pseudolite transmitter transmits the first phase modulated L-band signal during less than one half of the first period time duration, and for at least about 1 millisecond so that the first pseudolite transmitter transmits an epoch of the short period code during each transmission pulse. A receiver is adapted to receive the first phase modulated L-band signal from the first pseudolite transmitter, at times when it is not integrating phase modulated L-band signals from other GPS pseudolites transmitters, such that cross-correlation with other phase modulated L-band signals is minimized. Furthermore, the receiver is adapted to receive the L-band satellite signal during intervals when no pseudolite signals are being received.

Claims

1. A global positioning system (GPS) type navigation system comprising:

a first pseudolite transmitter adapted to transmit a first phase modulated L-band signal at a first signal pulse repetition rate, the first phase modulated L-band signal being modulated with a short period code having a code epoch of at least about one millisecond, the first signal pulse repetition rate having a first period time duration associated therewith, wherein for each of a plurality of consecutive transmission intervals having the first period time duration the pseudolite transmitter transmits the first phase modulated L-band signal during less than about one half of the first period time duration, and for at least about 1 millisecond so that the first pseudolite transmits an epoch of the short period code during each transmission pulse; and

a receiver adapted to receive the first phase modulated L-band signal.

2. The navigation system of claim 1, wherein the short period code is a C/A code.

3. The navigation system of claim 1, wherein the first signal pulse repetition rate is 50 pulses per second and the corresponding first period time duration is 20 milliseconds, the first pseudolite transmitter transmitting the first phase modulated L-band signal for between 1 millisecond and 10 milliseconds out of each 20 millisecond transmission interval.

4. The navigation system of claim 1, wherein the receiver is adapted to integrate received phase modulated L-band signals from GPS satellites during each of the plurality of consecutive transmission intervals only during portions of the transmission intervals in which the first pseudolite is not transmitting.

5. The navigation system of claim 1, and further comprising a plurality of pseudolite transmitters adapted to transmit modulated L-band signals at the first pulse repetition rate, wherein each of the plurality of pseudolite transmitters transmits its corresponding phase modulated L-band signal only during a corresponding portion of each of the plurality of consecutive transmission intervals, and wherein the corresponding portions of each of the plurality of consecutive transmission intervals during which the plurality of pseudolites transmit their respective phase modulated signals are non-overlapping.

6. The navigation system of claim 5, wherein a total of the corresponding portions of each transmission intervals during which the plurality of pseudolites transmit their respective phase modulated signals is less than about one half of the first period time duration.

7. The navigation system of claim 5, wherein the receiver is adapted to integrate received phase modulated L-band signals from one of the plurality of pseudolite transmitters during each of the plurality of consecutive transmission intervals only during the portion of the transmission intervals in which the others of the plurality of pseudolite transmitters are not transmitting.

8. The navigation system of claim 7, wherein the receiver is adapted to integrate received phase modulated L-band signals from one of the plurality of pseudolite transmitters during each of the plurality of consecutive transmission intervals substantially only during the portion of the transmission intervals in which the one of the plurality of pseudolite transmitters is transmitting.

9. The navigation system of claim 5, wherein the phase modulated L-band signal transmitted by at least one of the plurality of pseudolite transmitters is phase modulated using the C/A code for signal acquisition, and wherein the phase modulated L-band signal transmitted by at least two other of the plurality of pseudolite transmitters is phase modulated using the P(Y) code for navigation.

10. The navigation system of claim 1, wherein the signal pulse repetition rate is no greater than 200 pulses per second.

11. A pseudolite transmitter for use in a global positioning system (GPS) type navigation system, the pseudolite transmitter comprising:

an antenna; and

signal generating circuitry coupled to the antenna and adapted to generate and transmit through the antenna a first phase modulated L-band signal at a first signal pulse repetition rate, the first phase modulated L-band signal being modulated with a short period code having a code epoch of at least about one millisecond, the first signal pulse repetition rate having a first period time duration associated therewith, wherein for each of a plurality of consecutive transmission intervals having the first period time duration the signal generating circuitry transmits the first phase modulated L-band signal during less than about one half of the first period time duration, and for at least about 1 millisecond so that an epoch of the short period code is transmitted by the pseudolite transmitter during each transmission pulse.

12. The pseudolite transmitter of claim 11, wherein the short period code is a C/A code.

13. The pseudolite transmitter of claim 11, wherein the first signal pulse repetition rate is 50 pulses per second and the corresponding first period time duration is 20 milliseconds, the signal generating circuitry transmitting the first phase modulated L-band signal for between 1 millisecond and 10 milliseconds out of each 20 millisecond transmission interval.

14. The pseudolite transmitter of claim 11, wherein the signal pulse repetition rate is no greater than 200 pulses per second.

15. A global positioning system (GPS) receiver comprising:

an antenna which receives a first phase modulated L-band signal transmitted from a first pseudolite transmitter at a first signal pulse repetition rate, the first phase modulated L-band signal being modulated with a short period code having a code epoch of at least about one millisecond, the first signal pulse repetition rate having a first period time duration associated therewith, wherein for each of a plurality of consecutive transmission intervals having the first period time duration the antenna receives the first phase modulated L-band signal from the first pseudolite transmitter during less than about one half of the first period time duration, and for at least about 1 millisecond so that the received phase modulated L-band signal contains an epoch of the short period code during each transmission pulse;

signal processing circuitry coupled to the antenna, the signal processing circuitry receiving the first phase modulated L-band signal from the antenna and providing as an output a first frequency converted signal indicative of the first phase modulated L-band signal; and

integration circuitry coupled to the signal processing circuitry, the integration circuitry integrating the first frequency converted signal for less than one half of the first period time duration during each interval.

16. The GPS receiver of claim 15, wherein the antenna receives phase modulated L-band satellite signals from GPS satellites over the entire first period time duration of each consecutive transmission interval, wherein the signal processing circuitry receives the phase modulated L-band satellite signals and provides as an output frequency converted satellite signals indicative of the received phase modulated L-band satellite signals, and wherein the integration circuitry integrates the frequency converted satellite signals during each of the plurality of consecutive transmission intervals only during portions of the transmission intervals in which the first phase modulated L-band signal from the first pseudolite transmitter is not being received.

17. The GPS receiver of claim 15, wherein the antenna receives a plurality of phase modulated L-band signals from a plurality of pseudolite transmitters, each of the plurality of phase modulated L-band signals from the plurality of pseudolite transmitters being received during a corresponding and non-overlapping portion of each of the plurality of consecutive transmission intervals, wherein the integration circuitry integrates the first frequency converted signal only during the portion of the transmission intervals in which the others of the plurality of phase modulated L-band signals from the plurality of pseudolite transmitters are not being received.