Spread spectrum receiver with multi-bit correlator

• US 20040202235A1
• Filed: 04/30/2004
• Published: 10/14/2004
• Est. Priority Date: 04/25/1996
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Inventors: Kohli, Sanjai, Cahn, Charles R., Chansarkar, Mangesh, Chen, Steven, Turetsky, Greg
• Granted Patent: US 7,729,413 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 22/00 Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7095 Sliding correlator type
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04B 2201/70715 with application-specific features
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]
• CPC Class Codes: H04L 27/30 : wherein each code element is represented by a combination of frequencies

Abstract

A terrestrial C/A code GPS receiver system digitally samples, filters and stores a segment of 11 half chips of the received composite as a binary number and multiplexes this number for parallel correlation with each of a series of multibit code replicas for the satellites to be tracked. Each of the time delay specific correlation products are accumulated in a cell of a memory matrix so that at least twenty two delays for each satellite may be evaluated each code period providing fast reacquisition, even within a city intersection, as well as correction of multipath tracking and multipath interference. All cells of the memory matrix may be used for an acquisition of a single satellite in about 4 ms. Two satellite tracking, in addition to altitude hold, uses cross track hold alternating with clock hold to update the cross track estimate. Single satellite tracking uses cross track and clock hold together. Navigation data is updated with detected changes in motion including turns.

Claims

1-20. -20 (canceled)

21. A method for global positioning system (GPS) navigation, the method comprising:

tracking at least one GPS signal from a GPS satellite, including performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal; and

reacquiring the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization.

22. The method of claim 21 wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:

generating a plurality of code samples that are correlated with the at least one GPS signal; and

delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by the fraction of a chip.

23. The method of claim 21 wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:

generating a plurality of code samples that are correlated with the at least one GPS signal; and

delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by a multiple of the fraction of a chip.

24. The method of claim 22 wherein the fraction of a chip comprises less than one-half chip.

25. The method of claim 23 wherein the fraction of a chip comprises less than one-half chip.

26. The method of claim 21, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in one channel of a GPS receiver.

27. The method of claim 21, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in more than one channel of a GPS receiver.

28. The method of claim 21, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in more than one channel of a GPS receiver, wherein additional channels of the GPS receiver are concurrently used to track the at least one GPS signal.

29. An apparatus for global positioning system (GPS) navigation, the apparatus comprising:

a satellite receiver configured to receive GPS satellite signals;

a plurality of satellite tracking channels coupled to the satellite receiver, wherein each of the plurality of satellite tracking channels is configured to,

track at least one GPS signal from a GPS satellite, including performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal; and

reacquire the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization; and

a satellite processor coupled to receive outputs from the plurality of satellite tracking channels.

30. The apparatus of claim 29 wherein each of the plurality of satellite tracking channels is configured to:

generate a plurality of code samples that are correlated with the at least one GPS signal;

delay each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by the fraction of a chip.

31. The method of claim 29 wherein each of the plurality of satellite tracking channels is configured to:

generate a plurality of code samples that are correlated with the at least one GPS signal; and

delay each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by a multiple of the fraction of a chip.

32. The method of claim 30 wherein the fraction of a chip comprises less than one-half chip.

33. The method of claim 31 wherein the fraction of a chip comprises less than one-half chip.

34. The method of claim 29, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in one channel of the satellite tracking channels.

35. The method of claim 29, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in more than one channel of the satellite tracking channels.

36. The method of claim 29, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in more than one channel of the satellite tracking channels, wherein additional channels the satellite tracking channels are concurrently used to track the at least one GPS signal.

37. A computer readable medium having instructions stored thereon, which when executed control a global positioning system (GPS) navigation system, wherein controlling includes:

tracking at least one GPS signal from a GPS satellite, including performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal; and

reacquiring the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization.

38. The method of claim 37 wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:

generating a plurality of code samples that are correlated with the at least one GPS signal; and

delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by the fraction of a chip.

39. The method of claim 37 wherein the fraction of a chip comprises less than one-half chip.

40. The method of claim 38 wherein the fraction of a chip comprises less than one-half chip.

41. The method of claim 37, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in one channel of a GPS receiver.

42. The method of claim 37, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in more than one channel of a GPS receiver.

43. The method of claim 37, wherein the plurality of additional early correlations and the plurality of additional late correlations are performed in more than one channel of a GPS receiver, wherein additional channels of the GPS receiver are concurrently used to track the at least one GPS signal.

38-1. The method of claim 37 wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:

generating a plurality of code samples that are correlated with the at least one GPS signal; and

delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by a multiple of the fraction of a chip.