Apparatus for computing signal correlation at multiple resolutions

• US 7,184,464 B2
• Filed: 09/19/2003
• Issued: 02/27/2007
• Est. Priority Date: 05/18/2001
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Global Locate Incorporated (Broadcom, Inc.)
• Inventors: Abraham, Charles, Fuchs, Donald L.
• Primary Examiner(s): Kim; Kevin
• Application Number:
  US10/665,703
• Publication Number:
  US 20040077365A1
• Time in Patent Office: 1,257 Days
• Field of Search: 375/140, 375/142, 375/143, 375/150, 375/152, 375/147, 375/355
• US Class Current: 375/150
• CPC Class Codes: G01S 1/045 Receivers
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• 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 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A satellite signal receiver is described. A front end receives a satellite signal. A sampling circuit digitizes the satellite signal, where the digitized signal has either a first sample spacing or a second sample spacing. A mode selection process selects either the first sample spacing or the second sample spacing. A processor performs at least a subset of a convolution between a pseudorandom reference code and the digitized signal.

Claims

1. A satellite signal receiver, comprising:

a front end for receiving a satellite signal;

a sampling circuit for digitizing said satellite signal, said digitized signal having either a first sample spacing or a second sample spacing, said second sample spacing being narrower than said first sample spacing;

a mode selection processor for selecting (i) said first sample spacing when performing a convolution for an entire epoch of said satellite signal, and (ii) said second sample spacing when performing said convolution for less than an entire epoch of said satellite signal; and

a processor for performing at least a subset of a convolution between a pseudorandom reference code and said digitized signal;

wherein said sampling circuit comprises;

an analog to digital converter for sampling said satellite signal; and

a subsampling circuit for subsampling said sampled satellite signal to define said digitized signal having either said first sample spacing or said second sample spacing.

2. The satellite signal receiver of claim 1, further comprising:

a computer for computing a position location using results of said convolution.

18. The satellite signal receiver of claim 1, further comprising:

a plurality of processing channels, where each channel produces at least a subset of a convolution for a different satellite signal.

3. A satellite signal receiver, comprising:

a front end for receiving a satellite signal;

a sampling circuit for digitizing said satellite signal, said digitized signal having either a first sample spacing or a second sample spacing;

a mode selection processor for selecting either said first sample spacing or said second sample spacing;

a processor for performing at least a subset of a convolution between a pseudorandom reference code and said digitized signal; and

a computer for generating a region of interest in said digitized signal using results of said convolution in response to selection of said first sample spacing.

4. The satellite signal receiver of claim 3, wherein said processor is configured to perform at least a subset of a second convolution within said region of interest in response to selection of said second sample spacing.

5. The satellite signal receiver of claim 3, further comprising:

a plurality of processing channels, where each channel produces at least a subset of a convolution for a different satellite signal.

17. The satellite signal receiver of claim 3, wherein the computer is further configured to compute a position location using results of said convolution.

6. A receiver of global positioning system (GPS) signals, comprising:

an RF/IF converter for filtering and frequency translating a received GPS signal to form an IF signal;

an analog to digital converter for digitizing said IF signal;

a tuner for removing Doppler shift from said digitized signal and producing an in-phase (I) and a quadrature (Q) signal;

a decimation circuit for subsampling said I and Q signals, said subsampled and Q signals having either a first sample spacing or a second sample spacing, said second sample spacing being narrower than said first sample spacing;

a mode selection processor for selecting (i) said first sample spacing when performing a convolution for an entire epoch of said satellite signal, and (ii) said second sample spacing when performing a said convolution for less than an entire epoch of said satellite signal; and

a processor for performing at least a subset of a convolution between a C/A reference code and said subsampled I and Q signals.

7. The receiver of claim 6, wherein said processor comprises:

a code generator for producing a C/A reference code comprising a code lookup table and a first and a second code extender.

8. The receiver of claim 6, wherein said processor comprises:

a first shift register for storing a segment of said subsampled I signal; and

a second shift register for storing a segment of said subsampled Q signal.

9. The receiver of claim 6, further comprising:

a plurality of processing channels, where each channel produces at least a subset of a convolution for a different GPS signal.

10. The receiver of claim 6, further comprising:

a computer for computing a position location using said convolution.

11. The receiver of claim 6, further comprising:

a second processor for generating a region of interest in said subsampled I and Q signals using said convolution in response to selection of said first sample spacing.

12. The receiver of claim 11, wherein said processor is configured to perform at least a subset of a second convolution within said region of interest in response to selection of said second sample spacing.

13. The receiver of claim 6, further comprising:

a processing circuit for integrating results of said convolution.

14. A receiver of global positioning system (GPS) signals, comprising:

means for filtering and frequency translating a received GPS signal to form an IF signal;

means for digitizing said IF signal;

means for removing Doppler shift from said digitized signal and producing an in-phase (I) and a quadrature (Q) signal;

means for subsampling said I and Q signals, said subsampled I and Q signals having either a first sample spacing or a second sample spacing, said second sample spacing being narrower than said first sample spacing;

means for selecting (i) said first sample spacing when performing a convolution for an entire epoch of said satellite signal, and (ii) said second sample spacing when performing said convolution for less than an entire epoch of said satellite signal; and

means for performing at least a subset of a convolution between a C/A reference code and said subsampled I and Q signals.

15. The receiver of claim 14, further comprising:

means for generating a region of interest in said subsampled I and Q signals using said convolution in response to selection of said first sample spacing.

16. The receiver of claim 14, wherein said means for performing is configured to perform at least a subset of a second convolution within said region of interest in response to selection of said second sample spacing.