Direct acquistion of very large PN sequences in GPS systems

• US 6,369,752 B1
• Filed: 06/12/2000
• Issued: 04/09/2002
• Est. Priority Date: 05/28/1999
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Disselkoen, Brent A., Caldwell, William C.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/592,189
• Time in Patent Office: 666 Days
• Field of Search: 342/357.06, 342/357.12, 342/357.13, 342/357.15, 701/213, 701/215
• US Class Current: 342/357.69
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A receiver and method for acquiring a large pseudorandom (PN) sequence such as a GPS P(Y) code signal with poor or no knowledge of an external time reference are disclosed. A reference PN sequence is sectioned into a predetermined number of subsequences. The large PN sequence to be acquired is received from a remote source. The received PN sequence is correlated with each of the predetermined number of subsequences simultaneously. The large PN sequence is acquired, and a GPS solution may be provided, in the event the correlation produces a correlation between the received PN sequence and one of the predetermined number of subsequences. The large PN sequence may acquired without knowledge of an external time reference in a reasonable amount of time (e.g., less than ten minutes).

Claims

1. A GPS receiver, comprising:

a first filter and amplifier for selecting a predetermined frequency band of a received GPS signal and for amplifying the filtered signal;

a first converter for converting the received GPS signal into an intermediate frequency signal;

a second filter and amplifier for filtering and amplifying the intermediate frequency signal;

a second converter for converting the filtered and amplified intermediate frequency signal into a digital signal representative of the GPS signal; and

a processor for receiving the digital signal, said processor being configured to simultaneously correlate the digital signal with a plurality of subsequences of a reference signal such that the GPS signal is acquired upon correlation of the digital signal with one of the plurality of subsequences of the reference signal.

2. A GPS receiver as claimed in claim 1, further comprising a memory coupled with said processor, the plurality of subsequences of the reference signal being stored in said memory.

3. A GPS receiver as claimed in claim 1, the GPS signal being a P(Y) code sequence, said processor providing a GPS solution based upon the acquisition of the GPS signal.

4. A GPS receiver as claimed in claim 1, further comprising an in-phase and quadrature down converter for converting the intermediate frequency signal into in-phase and quadrature components.

5. A GPS receiver as claimed in claim 1, said processor being an optical processor.

6. A GPS receiver as claimed in claim 1, said processor being an application-specific integrated circuit.

7. A GPS receiver as claimed in claim 1, said processor being an analog processor.