Nearfield calibration method used for phased array antennas containing tunable phase shifters
First Claim
1. A method for calibrating a phased array antenna containing a plurality of electronically tunable phase shifters each of which is coupled to a column of radiating elements, said method comprising the steps of:
- measuring S-parameters for each of the phase shifters while varying the tuning voltage applied to each of the phase shifters in discrete steps across a tuning range;
generating phase-voltage equations for each of the phase shifters based on the measured S-parameters;
entering the phase-voltage equations into the controller;
calculating phase offsets for each column of radiating elements using a nearfield antenna range and the characterized data for each of the electronically tunable phase shifters; and
using the calculated phase offsets in a calibration table to adjust the tuning voltage of each of the electronically tunable phase shifters to cause the columns of radiating elements to yield a uniform beam.
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Abstract
A method for calibrating a phased array antenna and the calibrated phased array antenna are described herein. In the preferred embodiment of the present invention, the method for calibrating a phased array antenna containing a plurality of electronically tunable phase shifters each of which is coupled to a column of radiating elements includes the steps of: (a) characterizing each of the electronically tunable phase shifters; (b) calculating phase offsets for each column of radiating elements using a nearfield antenna range and the characterized data for each of the electronically tunable phase shifters; and (c) using the calculated phase offsets in a calibration table to adjust the tuning voltage of each of the electronically tunable phase shifters to cause the columns of radiating elements to yield a uniform beam.
275 Citations
28 Claims
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1. A method for calibrating a phased array antenna containing a plurality of electronically tunable phase shifters each of which is coupled to a column of radiating elements, said method comprising the steps of:
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measuring S-parameters for each of the phase shifters while varying the tuning voltage applied to each of the phase shifters in discrete steps across a tuning range;
generating phase-voltage equations for each of the phase shifters based on the measured S-parameters;
entering the phase-voltage equations into the controller;
calculating phase offsets for each column of radiating elements using a nearfield antenna range and the characterized data for each of the electronically tunable phase shifters; and
using the calculated phase offsets in a calibration table to adjust the tuning voltage of each of the electronically tunable phase shifters to cause the columns of radiating elements to yield a uniform beam. - View Dependent Claims (2, 3, 4, 5)
mounting said phased array antenna in the nearfield antenna range including a scanner probe positioned orthogonal to the phased array antenna in both azimuth and elevation directions.
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3. The method of claim 2, wherein said scanner probe is positioned a distance in the range of 0.25λ
- , to 50λ
, from an aperture of the phased array antenna, where λ
is a wavelength of a signal to be processed by the antenna.
- , to 50λ
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4. The method of claim 1, further comprising the steps of:
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performing a nearfield scan;
producing azimuth phase hologram plot;
comparing the azimuth phase hologram plot with a desired azimuth phase hologram plot; and
adjusting the calibration table if the azimuth phase hologram plot differs from the desired azimuth phase hologram plot.
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5. The method of claim 4, further comprising the steps of:
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performing farfield scan;
producing a farfield plot;
comparing the farfield plot with a desired farfield plot; and
repeating said characterizing step and said calculating step if the farfield plot differs from the desired farfield plot.
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6. A method for calibrating a phased array antenna containing a plurality of electronically tunable phase shifters each of which is coupled to a column of radiating elements and a controller for supplying a tuning voltage to the electronically tunable phase shifters, said method comprising the steps of:
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applying zero voltage to each of the phase shifters and measuring the phase of each of the plurality of columns of radiating elements in the phased array antenna;
using the measured phase to determine a phase target value for each of the plurality of columns of radiating elements in the phased array antenna;
adjusting a phase shift for each column of radiating elements in the phased array antenna to a value within a predetermined range of the phase target value to generate phase offset data; and
using the phase offset data to produce a calibration table for use in the controller to adjust the tuning voltage of each of the phase shifters to cause the columns of radiating elements to yield a uniform beam. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
generating phase-voltage equations for each of the phase shifters based on the measured S-parameters; and
entering the phase-voltage equations into an antenna control algorithm.
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8. The method of claim 7, wherein the step of generating phase-voltage equations for each of the phase shifters comprises the steps of:
plotting phase versus the applied tuning voltage; and
determining a best-fit line.
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9. The method of claim 8, wherein the best fit line is a third order polynomial.
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10. The method of claim 6, further comprising the step of:
positioning a scanner probe orthogonal to the phased array antenna in both azimuth and elevation directions.
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11. The method of claim 10, wherein said scanner probe is positioned a distance in the range of 0.25λ
- to 50λ
, from an aperture of the phased array antenna, where λ
is a wavelength of a signal to be processed by the phased array antenna.
- to 50λ
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12. The method of claim 10, wherein said scanner probe is positioned directly above the center of the column of radiating elements to be tested.
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13. The method of claim 6, wherein said step of adjusting the phase shift for each column of radiating elements comprises the step of:
measuring the phase offset of each of the phase shifters and adjusting the phase offset until a desired phase is measured.
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14. The method of claim 13, wherein said step of measuring the phase offset of each of the phase shifters comprises the step of:
making a microwave holography measurement to fine-tune the phase values so that a flat phase front is realized in a nearfield antenna measurement.
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15. The method of claim 13, wherein said step of measuring the phase offset of each of the phase shifters comprises the step of:
back transforming nearfield scan data to obtain phase values at the aperture of the antenna.
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16. The method of claim 6, further comprising the steps of:
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making a farfield antenna measurement and calculating a farfield plot; and
comparing the farfield plot to a desired farfield plot.
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17. A phased array antenna containing a plurality of electronically tunable phase shifters each of which is coupled to a column of radiating elements and a controller for supplying a tuning voltage to the electronically tunable phase shifters, said phased array antenna is calibrated by a method including the steps of:
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applying zero voltage to each of the phase shifters and measuring the phase of each of the plurality of columns of radiating elements in the phased array antenna;
using the measured phase to determine a phase target value for each of the plurality of columns of radiating elements in the phased array antenna;
adjusting a phase shift for each column of radiating elements in the phased array antenna to a value within a predetermined range of the phase target value to generate phase offset data; and
using the phase offset data to produce a calibration table for use in the controller to adjust the tuning voltage of each of the phase shifters to cause the columns of radiating elements to yield a uniform beam. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
measuring S-parameters for each of the phase shifters while varying a tuning voltage applied to each of the phase shifter in discrete steps across a tuning range;
generating phase-voltage equations for each of the phase shifters based on the measured S-parameters; and
entering the phase-voltage equations into an antenna control algorithm.
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19. The phased array antenna of claim 18, wherein said step of generating phase-voltage equations for each of the phase shifters comprises the steps of:
plotting phase versus the applied tuning voltage; and
determining a best-fit line.
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20. The phased array antenna of claim 19, wherein said best fit line is a third order polynomial.
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21. The method of claim 19, wherein said step of generating phase-voltage equations for each of the phase shifters comprises the steps of:
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plotting phase versus the applied tuning voltage; and
determining a best-fit line.
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22. The phased array antenna of claim 17, wherein said calibration method further comprises the step of:
positioning a scanner probe orthogonal to the phased array antenna in both azimuth and elevation directions.
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23. The phased array antenna of claim 22, wherein said scanner probe is positioned a distance in the range of 0.25λ
- , to 0.50λ
from an aperture of the phased array antenna, where is a wavelength of a signal to be processed by the phased array antenna.
- , to 0.50λ
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24. The phased array antenna of claim 22, wherein said scanner probe is positioned directly above the center of the column of radiating elements to be tested.
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25. The phased array antenna of claim 17, wherein said step of adjusting the phase shift for each column of radiating elements comprises the step of:
measuring the phase offset of each of the phase shifters and adjusting the phase offset until a desired phase is measured.
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26. The phased array antenna of claim 25, wherein said step of measuring the phase offset of each of the phase shifters comprises the step of:
making a microwave holography measurement to fine-tune the phase values so that a flat phase front is realized in a nearfield antenna measurement.
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27. The phased array antenna of claim 25, wherein said step of measuring the phase offset of each of the phase shifters comprises the step of:
back transforming nearfield scan data to obtain phase values at the aperture of the antenna.
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28. The phased array antenna of claim 17, further comprising the steps of:
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making a final farfield antenna measurement and calculating a farfield plot; and
comparing the farfield plot to a desired farfield plot.
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Specification