Method and apparatus for performing signal correlation

• US 20070160121A1
• Filed: 03/09/2007
• Published: 07/12/2007
• Est. Priority Date: 05/18/2001
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Global Locate Incorporated (Broadcom, Inc.)
• Inventors: Podshivalov, Sergei, Abraham, Charles, de la Porte, Serge
• Granted Patent: US 8,170,086 B2
• Time in Patent Office: Days
• 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 19/254 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: G01S 5/0205 Details
• 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 method of computing a correlation between a pseudorandom reference code and a satellite signal is provided. The method comprises receiving a satellite signal having a repeating code modulated thereon, wherein the satellite signal comprises a pseudorange; correlating the satellite signal with less than an entire length of the pseudorandom reference code with a portion of the satellite signal to produce a correlation over a period less than a period of the repeating code; and processing the correlation to form values representative of magnitude or power of the correlation to produce an energy signal.

Claims

1. A method of computing a correlation between a pseudorandom reference code and a satellite signal, the method comprising:

(a) receiving a satellite signal having a repeating code modulated thereon;

(b) correlating less than an entire length of a pseudorandom reference code with a portion of the satellite signal to produce a correlation.

2. The method of claim 1, further comprising:

(c) forming values representative of a magnitude or a power of the correlation to produce an energy signal;

(d) repeating steps (b) and (c) to produce a plurality of energy signals; and

(e) summing the plurality of energy signals as each energy signal is produced.

3. The method of claim 1, wherein step (b) comprises:

(b1) dividing the pseudorandom reference code into a plurality of code segments, where each segment is less than a period of the pseudorandom reference code;

(b2) selecting a code segment;

(b3) forming an inner product between the selected code segment and a portion of the repeating code of the satellite signal; and

(b4) repeating steps (b2) and (b3) to produce a plurality of inner products.

4. The method of claim 3, further comprising:

generating the code segments from a lookup table by selecting one of a fixed number of non-overlapping segments of less than the entire length of the pseudorandom code.

5. The method of claim 3, wherein the repeating code is a C/A code of a global positioning system.

6. The method of claim 5, wherein step (a3) comprises:

multiplying each sample in the portion of the C/A code with a respective chip of the selected code segment; and

summing each multiplication result with other multiplication results to produce the inner product.

7. The method of claim 1, wherein the period of the repeating code is 1 millisecond.

8. The method of claim 1, further comprising:

dividing the satellite signal into in-phase and quadrature components; and

separately performing step (b) on the in-phase and quadrature components.

9. Apparatus for computing a correlation between a pseudorandom reference code and a satellite signal comprising:

a satellite signal receiver for receiving a satellite signal having a repeating code modulated thereon;

a correlator for correlating less than an entire length of_a pseudorandom reference code with a portion of the satellite signal to produce a correlation.

10. The apparatus of claim 9, further comprising:

means for forming values representative of a magnitude or a power of the correlation to produce an energy signal;

means for repeating the utilization of the correlator to produce a plurality of energy signals; and

a summer for summing the plurality of energy signals as each energy signal is produced.

11. The apparatus of claim 9, where the correlator comprises:

a code generator for dividing the pseudorandom reference code into a plurality of code segments, where each segment is less than a period of the pseudorandom reference code and for selecting a code segment; and

a vector multiplier for forming an inner product between the selected code segment and a portion of the repeating code of the satellite signal.

12. The apparatus of claim 11 wherein the code generator further comprises:

a lookup table for storing and selecting one of a fixed number of non-overlapping segments of less than the entire length of the pseudorandom code.

13. The apparatus of claim 11, wherein the repeating code is a C/A code of a global positioning system.

14. The apparatus of claim 13 the vector multiplier comprises:

a multiplier for multiplying each sample in the portion of the C/A code with a respective chip of the selected code segment; and

a summer for summing each multiplication result with other multiplication results to produce the inner product.

15. The apparatus of claim 9, wherein the period of the repeating code is 1 millisecond.