PSEUDO RANDOM CODE MODULATED SIGNAL COMBINER

• US 20080062042A1
• Filed: 09/08/2006
• Published: 03/13/2008
• Est. Priority Date: 09/08/2006
• Status: Active Grant

• Current Assignee: Novatel Incorporated (Hexagon AB)
• Original Assignee: Novatel Incorporated (Hexagon AB)
• Inventors: O'Brien, Colin
• Granted Patent: US 7,358,893 B2
• Time in Patent Office: Days
• US Class Current: 342/357.06
• CPC Class Codes: G01S 19/53 Determining attitude

Abstract

A circuit and associated method for determining the heading of a vehicle or device with a satellite ranging system receiver is provided. The circuit requires only a single front end RF stage. A single RF stage can be used because the incoming signal received at the first antenna is delayed with respect to the signal received at the second antenna and the two signals are merged together, to form a combined signal. The combined signal can be down converted and sampled in a single stage. The samples are then separately correlated to detect the data associated with the portion of the signal attributed to each antenna. The differences between the measured data are then used to calculate the relative orientation (heading and pitch) of the device upon which the two antennas are disposed.

Claims

1. A circuit for receiving signals from two or more antennas that are mounted on a vehicle, for use with a satellite ranging system receiver, the circuit comprising:

a first antenna configured to receive signals from a set of satellites;

a second antenna configured to receive signals from the same set of satellites as said first antenna;

a time delay circuit coupled to said first antenna having a predetermined time delay such that a fixed delay is introduced into a first signal received at said first antenna with respect to a second signal received at said second antenna; and

a signal combiner configured to merge the delayed signal of the first antenna with the signal received by the second antenna to form a combined signal from which correlation measurements corresponding to the respective signals from the first and second antennas can be made for a given PRN code.

2. The circuit as defined in claim 1 further comprising

a single RF stage circuit coupled to an output of said signal combiner configured to receive said combined signal, and configured to down convert said combined signal to an intermediate frequency;

a sampling circuit having an A/D converter configured to obtain digitized samples of said combined signal;

compare circuits configured to correlate the digitized samples with respective local versions of a PRN code corresponding to a satellite PRN code to produce correlation measurements; and

a position and heading calculation processing circuit arrangement configured to receive the correlation measurements and to determine at least one of;

a position of the first antenna and a position of the second antenna, and the relative orientation of the antennas.

3. The circuit as defined in claim 2 wherein:

the position and heading calculation processing circuit arrangement is further configured to calculate the heading of the vehicle upon which the antennas are mounted based on the position information.

4. The circuit as defined in claim 2 wherein said fixed delay is equivalent to more than 1 code chip.

5. The circuit as defined in claim 2 further comprising

a first correlation channel including a first PRN code generator configured to produce a local PRN code which is correlated with the combined signal to track the PRN code of the first signal, and to obtain correlation measurements that are used to determine the position of the first antenna;

and

a second correlation channel including a second PRN code generator configured to produce a local version of a PRN code that precedes or trails the PRN code produced by said first PRN code generator by said fixed delay such that correlation measurements are obtained that correspond to the second signal and which are used to determine the position of the second antenna.

6. The circuit as defined in claim 2 further comprising

a correlation channel including a single PRN code generator configured to produce a local version of the PRN code corresponding to the PRN code of a satellite from which the first and second signals are received;

a delay element which introduces an adjusted delay which accounts for said fixed delay introduced into the first signal and for the differences in the times of arrival of the code to the first and second antennas;

a first compare circuit coupled to receive the PRN code and to produce a first set of correlation measurements; and

a second compare circuit coupled to receive the local code from the delayed PRN code from the delay element to obtain a second set of correlation measurements, whereby one or more of the range measurements and positions of the first antenna and the second antenna can be determined.

7. The circuit as defined in claim 1 wherein said circuit is deployed with respect to a rotating body.

8. A method of processing signals from two antennas located on a device using a satellite ranging system receiver, the method comprising the steps of:

disposing a first antenna in a first location on said device and disposing a second antenna on said device a given distance from the first antenna;

receiving at said first antenna, an incoming signal from a satellite;

selecting a predetermined amount by which to delay the incoming signal received at said first antenna, to produce a delayed signal;

receiving at said second antenna, an incoming signal from said satellite; and

combining the delayed signal with the signal received at the second antenna to produce a combined signal from which correlation measurements corresponding to the respective signals from the first and second antennas can be made for a given PRN code.

9. The method as defined in claim 8 wherein said predetermined delay is selected to be more than 1 code chip.

10. The method as defined in claim 8, comprising the further steps of:

downconverting the combined signal using a single RF stage including a local oscillator and a mixer to generate an intermediate frequency signal;

digitizing the intermediate frequency signal to obtain samples;

in a first channel, correlating the samples with a local version of the PRN code corresponding to the delayed PRN code from the first antenna to obtain data about the position of the first antenna;

in a second channel, correlating the samples with a local version of the PRN code corresponding to the PRN code from the second antenna to obtain pseudorange and carrier phase measurements from the second antenna; and

calculating the heading of the device using interferometric processing as is known in the art.

11. The method as defined in claim 8, comprising the further steps of:

downconverting the combined signal using a single RF stage including a local oscillator and a mixer to generate an intermediate frequency signal;

digitizing the intermediate frequency signal to obtain samples;

in a single channel, correlating the samples with a delayed local version of the PRN code corresponding to the PRN code from the satellite to obtain data about the position of the first antenna and correlating the samples with a local version of the PRN code corresponding to the PRN code from the satellite to obtain data about the position of the second antenna; and

calculating the heading of the device using interferometric processing between the first antenna and the second antenna.

12. The method as defined in claim 8 including the further step of providing said first antenna and said second antenna as antenna elements of a Local Area Augmentation Antenna.

13. The method as defined in claim 8 wherein said first and second antennas are disposed on a boat.

14. A system for processing signals from two antennas located on a device using a satellite ranging system receiver, comprising:

a first antenna disposed in a first location on said device and a second antenna disposed in a second position on said device a given distance from the first antenna;

means for receiving at said first antenna, an incoming signal from a satellite, and for selecting a predetermined amount by which to delay the incoming signal received at said first antenna, to produce a delayed signal and for receiving at said second antenna, an incoming signal from said satellite; and

means for merging the delayed signal with the signal received at the second antenna to produce a combined signal from which correlation measurements corresponding to the respective signals from the first and second antennas can be made for a given PRN code.

15. The system as defined in claim 14 wherein said predetermined delay is selected to be more than 1 code chip.

16. The system as defined in claim 14, further comprising:

means for downconverting the combined signal using a single RF stage including a local oscillator and a mixer to generate an intermediate frequency signal;

means for digitizing the intermediate frequency signal to obtain samples;

means, in a first channel, for correlating the samples with a local version of the PRN code corresponding to the delayed PRN code from the first antenna to obtain data about the position of the first antenna;

means, in a second channel, for correlating the samples with a local version of the PRN code corresponding to the PRN code from the second antenna to obtain data about the position of the second antenna; and

means for calculating the heading of the device using the position of the first antenna and the position of the second antenna.

17. The system as defined in claim 14, further comprising:

means for downconverting the combined signal using a single RF stage including a local oscillator and a mixer to generate an intermediate frequency signal;

means for digitizing the intermediate frequency signal to obtain samples;

means, in a single channel, for correlating the samples with a local version of the PRN code corresponding to the delayed PRN code from the first antenna to obtain data from the first antenna and further correlating the samples with a local version of the PRN code corresponding to the PRN code from the second antenna to obtain data from the second antenna; and

means for calculating the heading of the device using data of the first antenna and data of the second antenna.