Phased Array Antenna Calibration

• US 20170310004A1
• Filed: 04/21/2016
• Published: 10/26/2017
• Est. Priority Date: 04/21/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Swirhun, Paul, Feldman, Arnold
• Granted Patent: US 10,103,431 B2
• Time in Patent Office: Days
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H01Q 3/28 varying the amplitude
• CPC Class Codes: H01Q 3/36 with variable phase-shifters

Abstract

A method including identifying clusters of antenna elements of a phased array antenna. For each cluster of antenna elements, the method includes identifying a reference antenna element of the cluster of antenna elements and identifying pairs of calibration antenna elements of the cluster of antenna elements. For each pair of calibration antenna elements, the method includes executing a calibration routine configured to determine a calibration adjustment for each antenna element of the pair of calibration antenna elements based on the reference antenna element. The method also includes determining a leveling adjustment for each antenna element of the phased array antenna. The method further includes adjusting the element gain and the element phase of each antenna element of the phased array antenna based on the corresponding leveling adjustment to equalize a transmission gain and a transmission phase of each signal path of the phased array antenna.

Claims

1. A method comprising:

identifying clusters of antenna elements of a phased array antenna, the phased array antenna connected to a manifold configured to route signals between a manifold root and manifold terminals along corresponding signal paths, each manifold terminal connected to a corresponding transceiver of a respective antenna element of the phased array antenna, the manifold root having a root gain and a root phase;

for each cluster of antenna elements;

identifying a reference antenna element of the cluster of antenna elements;

identifying pairs of calibration antenna elements of the cluster of antenna elements, each pair of calibration antenna elements located equidistantly from the reference antenna element; and

for each pair of calibration antenna elements, executing, by data processing hardware, a calibration routine configured to determine a calibration adjustment for each antenna element of the pair of calibration antenna elements based on the reference antenna element, the calibration adjustment comprising;

a gain adjustment to equalize an element gain of the corresponding antenna element to the root gain of the manifold root; and

a phase adjustment to equalize an element phase of the corresponding antenna element to the root phase of the manifold root;

determining, by the data processing hardware, a leveling adjustment for each antenna element of the phased array antenna, the leveling adjustment comprising a gain-code and a phase-code based on an optimization of the calibration adjustment for the corresponding antenna element within the corresponding clusters of antenna elements; and

adjusting, by the data processing hardware, the element gain and the element phase of each antenna element of the phased array antenna based on the corresponding leveling adjustment to equalize a transmission gain and a transmission phase of each signal path of the phased array antenna.

2. The method of claim 1, wherein each gain adjustment comprises a deviation in the gain-code from a nominal gain value and each phase adjustment comprises a deviation in the phase-code form a nominal phase value.

3. The method of claim 1, wherein determining the leveling adjustment for each antenna element comprises:

populating, by the data processing hardware, a gain adjustment matrix with the gain adjustments;

populating, by the data processing hardware, a phase adjustment matrix with the phase adjustments, each adjustment matrix comprising columns and rows, each column corresponding to an antenna element and each row corresponding to a cluster of antenna elements; and

for each adjustment matrix;

adding, by the data processing hardware, a shift matrix to the adjustment matrix, the shift matrix aligning adjustments by antenna element;

averaging, by the data processing hardware, the adjustments of each column of the adjustment matrix; and

rounding each averaged adjustment to a nearest integer, the nearest integer being the corresponding gain-code or phase-code.

4. The method of claim 3, further comprising, for each adjustment matrix, minimizing a variance of each column subject to a constraint that relative offsets in a given row are maintained.

5. The method of claim 3, wherein each row of each adjustment matrix corresponds to a least-squares fitting of the corresponding adjustments of the corresponding cluster of the antenna elements.

6. The method of claim 1, wherein the clusters of antenna elements overlap.

7. The method of claim 1, wherein the reference antenna element is a transmitter antenna element and the pairs of calibration antenna elements are pairs of receiver antenna elements, and wherein the calibration routine comprises:

for each pair of receiver antenna elements;

transmitting a reference signal from the transmitter antenna element;

receiving the reference signal at the receiver antenna elements, the received reference signal at each receiver antenna element having a corresponding receive gain and a corresponding receive phase;

determining, by data processing hardware, the gain adjustments to equalize the respective element gains of each receiver antenna element to the root gain of the manifold root based on the receive gains; and

determining, by the data processing hardware, the phase adjustments to equalize the respective element phases of each receiver antenna element to the root phase of the manifold root based on the receive phases.

8. The method of claim 7, further comprising:

summing the received reference signals of the pair of receiver antenna elements;

receiving the summed signal in a peak detector; and

adjusting the element phase and/or the element gain of each receiver antenna element of the pair of receiver antenna elements based on an output of the peak detector.

9. The method of claim 8, further comprising adjusting the element phase of one of the receiver antenna elements of the pair of receiver elements so that the output of the peak detector is maximized.

10. The method of claim 8, further comprising:

shifting the element phase of one of the receiver antenna elements of the pair of receiver elements by 180 degrees; and

adjusting the element gain of the other of the receiver antenna elements of the pair of receiver elements so that the output of the peak detector is minimized.

11. The method of claim 1, wherein the reference antenna element is a receiver antenna element and the pairs of calibration antenna elements are pairs of transmitter antenna elements, and wherein the calibration routine comprises:

for each pair of transmitter antenna elements;

transmitting a reference signal from each transmitter antenna element of the pair of transmitter antenna elements;

receiving the reference signals at the receiver antenna element, each received reference signal at the receiver antenna element having a corresponding receive gain and a corresponding receive phase;

determining, by data processing hardware, the gain adjustments to equalize the respective element gains of each transmitter antenna element to the root gain of the manifold root based on the receive gains; and

determining, by the data processing hardware, the phase adjustments to equalize the respective element phases of each transmitter antenna element to the root phase of the manifold root based on the receive phases.

12. The method of claim 11, further comprising:

summing the received reference signals of the receiver antenna element;

receiving the summed signal in a peak detector; and

adjusting the element phase and/or the element gain of each transmitter antenna element of the pair of transmitter antenna elements based on an output of the peak detector.

13. The method of claim 12, further comprising adjusting the element phase of one of the transmitter antenna elements of the pair of transmitter elements so that the output of the peak detector is maximized.

14. The method of claim 12, further comprising:

shifting the element phase of one of the transmitter antenna elements of the pair of transmitter elements by 180 degrees; and

adjusting the element gain of the other of the transmitter antenna elements of the pair of transmitter elements so that the output of the peak detector is minimized.

15. An antenna system comprising:

a phased array antenna having antenna elements;

a manifold connected to the phased array antenna, the manifold having a manifold root and manifold terminals, the manifold configured to route signals between the manifold root and the manifold terminals along corresponding signal paths, each manifold terminal connected to a respective antenna element of the phased array antenna, the manifold root having a root gain and a root phase;

a calibration module in communication with the manifold and the phased array antenna, the calibration module configured to perform operations comprising;

identifying clusters of antenna elements of the phased array antenna;

for each cluster of antenna elements;

identifying a reference antenna element of the cluster of antenna elements;

identifying pairs of calibration antenna elements of the cluster of antenna elements, each pair of calibration antenna elements located equidistantly from the reference antenna element; and

for each pair of calibration antenna elements, executing a calibration routine configured to determine a calibration adjustment for each antenna element of the pair of calibration antenna elements based on the reference antenna element, the calibration adjustment comprising;

a gain adjustment to equalize an element gain of the corresponding antenna element to the root gain of the manifold root; and

a phase adjustment to equalize an element phase of the corresponding antenna element to the root phase of the manifold root;

determining a leveling adjustment for each antenna element of the phased array antenna, the leveling adjustment comprising a gain-code and a phase-code based on an optimization of the calibration adjustment for the corresponding antenna element within the corresponding clusters of antenna elements; and

adjusting the element gain and the element phase of each antenna element of the phased array antenna based on the corresponding leveling adjustment.

16. The antenna system of claim 15, wherein each gain adjustment comprises a deviation in the gain-code from a nominal gain value and each phase adjustment comprises a deviation in the phase-code form a nominal phase value.

17. The antenna system of claim 15, wherein determining the leveling adjustment for each antenna element comprises:

populating, by the data processing hardware, a gain adjustment matrix with the gain adjustments;

populating, by the data processing hardware, a phase adjustment matrix with the phase adjustments, each adjustment matrix comprising columns and rows, each column corresponding to an antenna element and each row corresponding to a cluster of antenna elements; and

for each adjustment matrix;

adding, by the data processing hardware, a shift matrix to the adjustment matrix, the shift matrix aligning adjustments by antenna element;

averaging, by the data processing hardware, the adjustments of each column of the adjustment matrix; and

rounding each averaged adjustment to a nearest integer, the nearest integer being the corresponding gain-code or phase-code.

18. The antenna system of claim 17, wherein determining the leveling adjustment for each antenna element further comprises, for each adjustment matrix, minimizing a variance of each column subject to a constraint that relative offsets in a given row are maintained.

19. The antenna system of claim 17, wherein each row of each adjustment matrix corresponds to a least-squares fitting of the corresponding adjustments of the corresponding cluster of the antenna elements.

20. The antenna system of claim 15, wherein the clusters of antenna elements overlap.

21. The antenna system of claim 15, wherein the reference antenna element is a transmitter antenna element and the pairs of calibration antenna elements are pairs of receiver antenna elements, and wherein the calibration routine comprises:

for each pair of receiver antenna elements;

transmitting a reference signal from the transmitter antenna element;

receiving the reference signal at the receiver antenna elements, the received reference signal at each receiver antenna element having a corresponding receive gain and a corresponding receive phase;

determining the gain adjustments to equalize the respective element gains of each receiver antenna element to the root gain of the manifold root based on the receive gains; and

determining the phase adjustments to equalize the respective element phases of each receiver antenna element to the root phase of the manifold root based on the receive phases.

22. The antenna system of claim 21, wherein the calibration routine comprises further comprises:

summing the received reference signals of the pair of receiver antenna elements;

receiving the summed signal in a peak detector; and

adjusting the element phase and/or the element gain of each receiver antenna element of the pair of receiver antenna elements based on an output of the peak detector.

23. The antenna system of claim 22, wherein the calibration routine comprises further comprises adjusting the element phase of one of the receiver antenna elements of the pair of receiver elements so that the output of the peak detector is maximized.

24. The antenna system of claim 22, wherein the calibration routine comprises further comprises:

shifting the element phase of one of the receiver antenna elements of the pair of receiver elements by 180 degrees; and

adjusting the element gain of the other of the receiver antenna elements of the pair of receiver elements so that the output of the peak detector is minimized.

25. The antenna system of claim 15, wherein the reference antenna element is a receiver antenna element and the pairs of calibration antenna elements are pairs of transmitter antenna elements, and wherein the calibration routine comprises:

for each pair of transmitter antenna elements;

transmitting a reference signal from each transmitter antenna element of the pair of transmitter antenna elements;

receiving the reference signals at the receiver antenna element, each received reference signal at the receiver antenna element having a corresponding receive gain and a corresponding receive phase;

determining the gain adjustments to equalize the respective element gains of each transmitter antenna element to the root gain of the manifold root based on the receive gains; and

determining the phase adjustments to equalize the respective element phases of each transmitter antenna element to the root phase of the manifold root based on the receive phases.

26. The antenna system of claim 25, wherein the calibration routine comprises further comprises:

summing the received reference signals of the receiver antenna element;

receiving the summed signal in a peak detector; and

adjusting the element phase and/or the element gain of each transmitter antenna element of the pair of transmitter antenna elements based on an output of the peak detector.

27. The antenna system of claim 26, wherein the calibration routine comprises further comprises adjusting the element phase of one of the transmitter antenna elements of the pair of transmitter elements so that the output of the peak detector is maximized.

28. The antenna system of claim 26, wherein the calibration routine comprises further comprises:

shifting the element phase of one of the transmitter antenna elements of the pair of transmitter elements by 180 degrees; and

adjusting the element gain of the other of the transmitter antenna elements of the pair of transmitter elements so that the output of the peak detector is minimized.