METHODS AND SYSTEMS FOR FREQUENCY INDEPENDENT BEARING DETECTION

• US 20080204310A1
• Filed: 01/02/2008
• Published: 08/28/2008
• Est. Priority Date: 02/28/2007
• Status: Active Grant

• Current Assignee: Garmin International, Inc. (Garmin Limited)
• Original Assignee: Garmin International, Inc. (Garmin Limited)
• Inventors: Needham, Edward W., Hou, Weiguang, Blessing, John C.
• Granted Patent: US 7,825,858 B2
• Time in Patent Office: Days
• US Class Current: 342/195
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G01S 7/2886 using I/Q processing

Abstract

A system and method are provided for estimating bearing of a target based on RF signals received by an array of antenna elements. The system comprises first and second input channels that are configured to receive analog signals that correspond to first and second antenna elements. The system also includes an analog to digital converter module for converting each of the analog signals to digital data samples and outputting separate streams of digital data samples corresponding to each of the first and second antenna elements as first and second data streams. An in-phase and quadrature detector module includes a phase shift module for shifting each of the first and second data streams by a predetermined amount of time to form first and second phase shifted data streams. A surveillance module determines a bearing of the target based on in-phase and quadrature data.

Claims

1. A system for estimating bearing of a target based on RF signals received by an array of antenna elements, the system comprising:

first and second analog lines for receiving analog signals corresponding to first and second antenna elements within the antenna element array;

an A/D converter module for converting each of the analog signals to digital data and for outputting separate digital data streams corresponding to each of the first and second antenna elements;

a phase shift module for shifting each of the first and second data streams by a predetermined amount of time to form first and second phase shifted data streams,

a phase detector module for calculating in-phase (I) data based on the first and second data streams and for calculating quadrature (Q) data based on the first and second data streams and the first and second phase shifted data streams; and

a surveillance module for determining a bearing of the target based on the I and Q data.

2. The system of claim 1, wherein the phase detector module is implemented on a field programmable gate array programmed to function as a digital phase interferometer.

3. The system of claim 1, wherein the phase detector module calculates a mixed in-phase data stream by multiplying the first and second data streams.

4. The system of claim 3, wherein the phase detector module includes a delay module that delays the mixed in-phase data stream by a fixed time delay to output the delayed mixed in-phase data stream.

5. The system of claim 4, wherein the phase detector module calculates the I data by low-pass filtering the sum of the mixed in-phase data stream and the delayed mixed in-phase data stream.

6. The system of claim 1, wherein the phase detector module includes first and second delay modules that delay the first and second data streams, respectively, by a fixed time delay to output the first and second phase shifted data streams, the digital phase detector module calculating the Q data based on the first and second data streams and the first and second phase shifted data streams.

7. The system of claim 1, wherein the phase detector module calculates a first pseudo-quadrature component by multiplying the first phase shifted data stream and the second data stream and calculates a second pseudo-quadrature component by multiplying the second phase shifted data stream and the first data stream.

8. The system of claim 7, wherein the phase detector module calculates the Q data by subtracting the first pseudo-quadrature component and the second pseudo-quadrature component.

9. The system of claim 1, wherein the phase detector module low-pass filters the pre-filtered I data to form filtered I data and low-pass filters the pre-filtered Q data to form filtered Q data, the surveillance module calculating the bearing based on the filtered I and Q data.

10. The system of claim 1, wherein the input channels are configured to receive high frequency analog signals from the individual corresponding antenna elements, the system further comprising down converters, provided along the input channels, down converting the high frequency analog signals to intermediate frequency analog signals before being conveyed to the A/D converter module.

11. The system of claim 1, wherein the surveillance module determines phase values based on arctangents of the I and Q data, and determines the bearing based on the arctangent of the phase values.

12. A method for estimating bearing of a target based on RF signals received by an array of antenna elements, the method comprising:

receiving analog signals from first and second antenna elements within an antenna element array;

converting each of the analog signals to digital data and outputting separate digital data streams corresponding to each of the first and second antenna elements;

shifting each of the first and second data streams by a predetermined amount of time to form first and second phase shifted data streams;

calculating in-phase (I) data based on the first and second data streams;

calculating quadrature (Q) data based on the first and second data streams and the first and second phase shifted data streams; and

determining a bearing of the target based on the I and Q data.

13. The method of claim 12, further comprising calculating a mixed in-phase data stream by multiplying the first and second data streams.

14. The method of claim 13, further comprising delaying the mixed in-phase data stream by a fixed time delay to output the delayed mixed in-phase data stream.

15. The method of claim 14, further comprising calculating the I data by low-pass filtering the sum of the mixed in-phase data stream and the delayed mixed in-phase data stream.

16. The method of claim 12, further comprising delaying the first and second data streams, respectively, by a fixed time delay to output the first and second phase shifted data streams, and calculating the Q data based on the first and second data streams and the first and second phase shifted data streams.

17. The method of claim 12, further comprising calculating a first pseudo-quadrature component by multiplying the first phase shifted data stream and the second data stream, calculating a second pseudo-quadrature component by multiplying the second phase shifted data stream and the first data stream.

18. The method of claim 17, wherein calculating the Q data comprises subtracting the first pseudo-quadrature component and the second pseudo-quadrature component.

19. The method of claim 12, further comprising low-pass filtering the pre-filtered I data to form filtered I data, low-pass filtering the pre-filtered Q data to form filtered Q data, and calculating the bearing based on the filtered I and Q data.

20. The method of claim 12, wherein the antenna elements receive high frequency analog signals, the method further comprising down converting the high frequency analog signals to intermediate frequency analog signals before being converted to the digital data samples.

21. The method of claim 12, further comprising determining phase values based on the arctangents of the I and Q data, and determining the bearing based on the arctangent of the phase values.

22. A method for estimating bearing of a target based on RF signals received by an array of antenna elements, the method comprising:

receiving analog signals from first and second antenna elements within an antenna element array;

converting each of the analog signals to digital data and outputting separate digital data streams corresponding to each of the first and second antenna elements;

calculating pre-filtered in-phase data by mixing the first and second data streams and summing the mixed first and second data stream with a time delayed mixed first and second data stream;

shifting each of the first and second data streams by a predetermined amount of time to form first and second phase shifted data streams;

calculating a first pseudo-quadrature component by multiplying the first phase shifted data stream and the second data stream;

calculating a second pseudo-quadrature component by multiplying the second phase shifted data stream and the first data stream;

calculating pre-filtered difference pseudo-quadrature data by subtracting the first pseudo-quadrature component and the second pseudo-quadrature component;

calculating pre-filtered summed pseudo-quadrature data by summing the first pseudo-quadrature component and the second pseudo-quadrature component;

calculating I, Q, and A data by filtering the pre-filtered in-phase data, the pre-filtered difference pseudo-quadrature data, and the pre-filtered summed pseudo-quadrature data, respectively; and

determining a bearing of the target based on the I, Q, and A data.

23. A system for estimating bearing of a target based on RF signals received by an array of antenna elements, the system comprising:

first and second analog lines for receiving analog signals corresponding to first and second antenna elements within the antenna element array;

an A/D converter module for converting each of the analog signals to digital data and for outputting separate digital data streams corresponding to each of the first and second antenna elements;

a phase shift module operable for shifting each of the first and second data streams by a predetermined amount of time to form first and second phase shifted data streams;

a phase detector module operable for—

calculating pre-filtered in-phase data based on the first and second data streams,

calculating pre-filtered quadrature data based on the first and second data streams and the first and second phase shifted data streams, and

calculating I and Q data by filtering the in-phase data and the quadrature-data; and

a surveillance module for determining a bearing of the target based on the I and Q data.