Method and apparatus for signal receipt and acquisition

• US 7,733,940 B2
• Filed: 12/13/2002
• Issued: 06/08/2010
• Est. Priority Date: 12/22/2001
• Status: Expired due to Fees

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Yule, Andrew T., Dooley, Saul R., Sarkar, Amites
• Primary Examiner(s): Ghayour, Mohammad H
• Assistant Examiner(s): Malek, Leila
• Application Number:
  US10/319,895
• Publication Number:
  US 20030128743A1
• Time in Patent Office: 2,734 Days
• Field of Search: 375/147, 375/130, 375/316, 370/210, 370/320, 370/342, 342/196, 702/77, 708/403, 708/404
• US Class Current: 375/147
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70715 with application-specific features
• CPC Class Codes: H04L 2027/0065 Frequency error detectors H04L2027/0067 takes precedence

Abstract

The present invention provides for a method of receiving a signal spread over a frequency range, and in particular a direct sequence spread spectrum signals including the step of employing a Fast Fourier Transform (FFT) in the Doppler search. In particular, the invention relates to the receipt of spread spectrum signals such as those transmitted as part of a GPS system.

Claims

1. A method of receiving a signal by detection of a carrier frequency, the method comprising:

employing a first fast Fourier transform (FFT) combiner to determine the carrier frequency;

driving the first FFT combiner with a first frequency generator; and

employing at least one further FFT combiner;

driving the at least one further FFT combiner with a second frequency generator, wherein the first and second frequency generators are mutually offset in frequency such that a sensitivity loss that is incurred by the at least one further FFT combiner has maxima at Doppler error values where a sensitivity loss that is incurred by the first FFT combiner has dips and the sensitivity loss that is incurred by the first FFT combiner has maxima at Doppler error values where the sensitivity loss that is incurred by the at least one further FFT combiner has dips, wherein the employing the at least one further FFT combiner with the first FFT combiner reduces a scalloping loss.

2. A method as claimed in claim 1, wherein the frequency offset is ½

T_i Hz, wherein T_i represents an integration time of the receiver.

3. A method as claimed in claim 1 and employing two further FFT combiners so as to provide a triple FFT combiner.

4. A method as claimed in claim 3, wherein the offset is ⅓

T_i Hz, wherein T_i represents an integration time of the receiver.

5. A method as claimed in claim 1, and employing three further FFT combiners to provide a quadruple FFT combiner.

6. A method as claimed in claim 5, wherein the frequency offset of each combiner is ¼

T_i Hz, wherein T_i represents an integration time of the receiver.

7. A method as claimed in claim 1, wherein the signal comprises a direct sequence spread spectrum signal.

8. A method as claimed in claim 1, wherein the carrier to be detected comprises a data and a (pseudo random noise) PRN modulated carrier.

9. A method as claimed in claim 1, wherein the signal to be received comprises a spread spectrum signal.

10. A signal receiver for receiving a signal by means of detection of a carrier frequency and comprising:

a first fast Fourier transform (FFT) combiner to determine the carrier frequency;

a first frequency generator configured to drive the first FFT combiner;

a second FFT combiner;

a second frequency generator configured to drive the second FFT combiner, wherein the first and second frequency generators are mutually offset such that a sensitivity loss that is incurred by the second FFT combiner has maxima at Doppler error values where a sensitivity loss that is incurred by the first FFT combiner has dips and the sensitivity loss that is incurred by the first FFT combiner has maxima at Doppler error values where the sensitivity loss that is incurred by the second FFT combiner has dips, using the second FFT combiner with the first FFT reduces a scalloping loss.

11. A receiver as claimed in claim 10, wherein the frequency offset is ½

T_i Hz, wherein T_i represents an integration time of the receiver.

12. A global position system (GPS) device, comprising:

a receiver having;

a first Fast Fourier Transform (FFT) combiner;

a first frequency generator configured to drive the first FFT combiner;

a second FFT combiner;

a second frequency generator configured to drive the second FFT combiner,

wherein the first and second frequency generators are mutually offset such that a sensitivity loss that is incurred by the second FFT combiner has maxima at Doppler error values where a sensitivity loss that is incurred by the first FFT combiner has dips and the sensitivity loss that is incurred by the first FFT combiner has maxima at Doppler error values where the sensitivity loss that is incurred by the second FFT combiner has dips, using the second FFT combiner with the first FFT combiner reduces a scalloping loss.

13. A GPS device as claimed in claim 12, further comprising one additional FFT combiners, which provide a triple FFT combiner.

14. A GPS device as claimed in claim 12, further comprising two additional FFT combiners, which provide a quadruple FFT combiner.