Cost-effective and highly accurate antenna with built-in calibration for V2X communications

This paper presents a phased array system (PAS) with built-in calibration to reduce cost and improve the accuracy for vehicle-to-everything (V2X) communications. Unlike other high-complexity and high-cost calibration methods, our proposed built-in calibration achieves a lower cost and low complexity by detecting only the magnitude. Conventional built-in calibration uses a mixer, thus causing high power consumption and high cost. However, our proposed built-in calibration method searches for the minimum of the vector-sum point from the signal by sampled lines on-board, resulting in a higher accuracy. The vector-sum point goes to a minimum when the phase and magnitude are in balance. Therefore, the phase and magnitude imbalance can be easily monitored by controlling phase shifters and attenuators in PAS. To verify our proposed built-in calibration in PAS, a T/Rx with four RF-chains and sampled lines was fabricated at 5.8 GHz. Its performance was then demonstrated through simulated and measured results. Moreover, a communication performance evaluation using an actual vehicle was performed both before and after calibration. As a result, we found that a signal without distortion was transmitted after calibration.