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Phased Array Antenna Calibration Technique Based on Center-Null-Tracking (CNT) Method

In this paper, a new phased array antenna calibration technique using a center-null-tracking (CNT) method is proposed. The proposed CNT method is based on the comparison of two antenna elements in array with a phase difference of 180°. The deviation from 180° phase difference can be considered as a phase error and can also be detected. Since the radiation pattern of two antenna elements in 180° phase difference generates a null in the center, tacking the null location by monitoring the magnitude of the null can determine the unwanted phase error. Once the phase error is found, the magnitude error between the antenna element can also be determined by measuring the magnitude of the null again by changing attenuation level in the phased array. If the two elements have an imbalance in magnitude, the null magnitude is not at minimum. So, by controlling attenuators to see whether the null magnitude decreases or increases, magnitude balance can also be achieved. In order to verify the proposed calibration technique, 1x4 array antenna is simulated and tested at 5.8 GHz. Both of the simulated and measured result show excellent performance comparing to the conventionally used Rotating-Element Electric-field Vector (REV) method.