Analog compression of GPS C/A signal to audio bandwidth

• US 7,436,907 B1
• Filed: 08/23/2001
• Issued: 10/14/2008
• Est. Priority Date: 08/24/2000
• Status: Expired due to Fees

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Norman, Charles P.
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US09/938,387
• Time in Patent Office: 2,609 Days
• Field of Search: 375/316, 375324-326, 375/340, 342/352, 342/357.06
• US Class Current: 375/324
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain

Abstract

The present invention discloses analog methods and circuits for compression of the GPS C/A signal to audio bandwidths to improve TTFF times, as well as decreasing auto correlation errors in systems that employ the methods and devices disclosed.

Claims

1. An apparatus for compressing a Global Positioning System (GPS) signal comprising:

a first mixer for removing a carrier component of the GPS signal;

a second mixer for receiving the carrier-removed GPS signal and a separately received frequency reference signal that is received at the apparatus separately from the GPS signal and outputting a resultant signal;

a comb filter, coupled to the second mixer, for filtering the resultant signal and obtaining a first output comprising filter lines; and

a frequency shifter for shifting the filter lines in the first output to produce a compressed GPS signal.

2. The apparatus of claim 1, further comprising a second frequency shifter for shifting the compressed GPS signal to produce a second compressed GPS signal.

3. The apparatus of claim 2, wherein the comb filter filters the carrier-removed GPS signal that has been combined with the reference frequency signal received from a remote location via a wireless communication link, and using the reference frequency signal from the remote location to shift the carrier-removed GPS signal received at the comb filter to an expected location of the filter lines of the first output.

4. The apparatus of claim 3, wherein the frequency shifting of the filter lines comprises mixing the filter lines with at least one output of a frequency generator.

5. A receiver comprising:

at least one antenna for receiving a GPS signal from GPS satellites and for sending and receiving radio signals over a radio link to a base station, the radio signals including a frequency reference signal;

a first mixer for removing a carrier component of the GPS signal;

a second mixer for receiving the carrier-removed GPS signal and the frequency reference signal and outputting a resultant signal;

a comb filter, coupled to the second mixer, for filtering the resultant signal and obtaining a first output comprising filter lines; and

a frequency shifter for shifting the filter lines in the first output to produce a compressed GPS signal.

6. The receiver of claim 5 where the at least one antenna includes a GPS antenna for receiving the GPS signal and a wireless communications antenna for communicating the radio link.

7. The receiver of claim 5 further comprising:

a transmitter coupled to the at least one antenna to communicate the compressed GPS signal to the base station.

8. The receiver of claim 5, further comprising a second frequency shifter for shifting the compressed GPS signal to produce a second compressed GPS signal.

9. The receiver of claim 8, wherein the comb filter filters the carrier-removed GPS signal that have been combined with the reference frequency signal received from a remote location via a wireless communication link, and using the reference frequency signal from the remote location to shift the carrier-removed GPS signal received at the comb filter to an expected location of the filter lines of the first output.

10. The receiver of claim 9, wherein the frequency shifting of the filter lines comprises mixing the filter lines with at least one output of frequency generator.