SYSTEM AND METHOD FOR DEMODULATING CODE SHIFT KEYING DATA FROM A SATELLITE SIGNAL UTILIZING A BINARY SEARCH

• US 20200136672A1
• Filed: 12/23/2019
• Published: 04/30/2020
• Est. Priority Date: 09/26/2018
• Status: Active Grant

• Current Assignee: Novatel Incorporated (Hexagon AB)
• Original Assignee: Novatel Incorporated (Hexagon AB)
• Inventors: Fenton, Patrick C., Brown, David
• Granted Patent: US 10,784,922 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 19/243 Demodulation of navigation message
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/7073 Direct sequence modulation synchronisation

Abstract

A Global Navigation Satellite System (GNSS) receiver demodulates code shift keying (CSK) data utilizing a binary search. The GNSS receiver receives a signal including a pseudorandom noise (PRN) code modulated by code shift keying (CSK) to represent a symbol (i.e., CSK modulated symbol). The GNSS receiver maintains a plurality of receiver codes each representing a different shift in chips to the PRN code. The GNSS receiver performs a linear combination of portions of the receiver codes. In an embodiment, the GNSS receiver compares correlation power level value for respective portions of the receiver codes to demodulate the CSK data. In a further embodiment, the GNSS receiver compares the correlation power level values for portions of receiver codes with power detection threshold values to demodulate the CSK data. In a further embodiment, the GNSS receiver utilizes signs of the correlation power level values to demodulate the CSK data.

Claims

1. An apparatus comprising:

a processor coupled to a memory, the processor configured to;

perform a chip-by-chip linear combination of a plurality of receiver codes to generate a combinational code, wherein each of the plurality of receiver codes is a different shift in chips to a predetermined code,

correlate an L6 satellite signal with the combinational code to produce a power correlation value, wherein the L6 satellite signal is received from a Global Navigation Satellite Signal (GNSS) satellite associated with a Quasi-Zenith Satellite System (QZSS);

determine that the L6 satellite signal is present in response to the power correlation value being greater than a threshold value; and

determine that the L6 satellite signal is lost in response to the power correlation value being less than or equal to the threshold value.

2. The apparatus of claim 1, wherein the predetermined code is a pseudorandom noise (PRN) code.

3. The apparatus of claim 1, wherein the L6 satellite signal is a L62 satellite signal.

4. The apparatus of claim 1, wherein each chip of the combinational code is multiple bits or a single bit.

5. The apparatus of claim 1, wherein the chip-by-chip linear combination of the plurality of receiver codes is a chip-by-chip summation of the plurality of receiver codes.

6. The apparatus of claim 1, wherein the processor is further configured to demodulate code shift keying data from the L6 satellite signal in response to determining that the L6 satellite signal is present.

7. A method, comprising:

performing a first chip-by-chip linear combination of a first selected number of a plurality of receiver codes to generate a first combinational code, wherein each of the plurality of receiver codes is a different shift in chips to a predetermined code,

performing a second chip-by-chip linear combination of a second selected number of the plurality of receiver codes to generate a second combinational code,

correlating an L6 satellite signal with the first combinational code to produce a first power correlation value and correlating the L6 satellite signal with the second combinational code to produce a second power correlation value, wherein the satellite signal is received from a Global Navigation Satellite Signal (GNSS) satellite associated with a Quasi-Zenith Satellite System (QZSS);

determining that the L6 satellite signal is lost in response to the first power correlation value and the second power correlation value being less than or equal to the threshold value.

8. The method of claim 7, wherein the predetermined code is a pseudorandom noise (PRN) code, and wherein the first selected number of the plurality of receiver codes and the second selected number of the plurality of receiver codes together include all of the plurality of receiver codes.

9. The method of claim 7, wherein the L6 satellite signal is a L62 satellite signal.

10. The method of claim 7, wherein each chip of the first combinational code and the second combinational code is multiple bits or a single bit.

11. The method of claim 7, wherein the first chip-by-chip linear combination of the first selected number of the plurality of receiver codes and the second chip-by-chip linear combination of the second selected number of the plurality of receiver codes are chip-by-chip summations.

12. The method of claim 7, further comprising determining that the L6 satellite signal is present in response to the first power correlation value or the second power correlation value being greater than the threshold value.

13. The method of claim 12, further comprising demodulating code shift keying data from the L6 signal in response to determining that the L6 satellite signal is present.

14. An apparatus comprising:

a processor coupled to a memory, the processor configured to;

perform a first chip-by-chip linear combination of a first selected number of a plurality of receiver codes to generate a first combinational code, wherein each of the plurality of receiver codes is a different shift in chips to a predetermined code, perform a second chip-by-chip linear combination of a second selected number of the plurality of receiver codes to generate a second combinational code,

produce a first power correlation value based on a correlation of a received signal with the first combinational code and produce a second power correlation value based on the correlation of the received signal with the second combinational code;

determine that the received signal is present for demodulation in response to the first power correlation value or the second power correlation value being greater than a threshold value; and

determine that the received signal is lost in response to the first power correlation value and the second power correlation value being less than or equal to the threshold value.

15. The apparatus of claim 14, wherein the received signal is an L62 satellite signal received from a Global Navigation Satellite Signal (GNSS) satellite associated with a Quasi-Zenith Satellite System (QZSS).

16. The apparatus of claim 15, wherein the processor is further configured to demodulate code shift keying data from the L62 satellite signal in response to determining that the received signal is present for demodulation.

17. The apparatus of claim 14, wherein the predetermined code is a pseudorandom noise (PRN) code.

18. The apparatus of claim 14, wherein each chip of the combinational code is multiple bits or a single bit.

19. The apparatus of claim 14, wherein the first chip-by-chip linear combination of the first selected number of the plurality of receiver codes is a chip-by-chip summation of the first selected number of the plurality of receiver codes.

20. The apparatus of claim 19, wherein the second chip-by-chip linear combination of the second selected number of the plurality of receiver codes is the chip-by-chip summation of the second selected number of the plurality of receiver codes.