Wideband Phased Array Calibration Method for Digital Beamforming

Previous study has used chirp signals to characterize the RF response of a multi-channel RF receiver [1]. The results showed a significant channel imbalance. After applying a time-reversal filter, the channel imbalance was remedied and both phase and amplitude were realigned among the channels. In the present study, the RF response of a complete multi-channel receiver with antenna was characterized. A 1-8 GHz phased array antenna was mounted in an anechoic chamber and a chirp signal was used to measure the frequency response of each channel as a function of azimuth angle. Each channel's response was equalized using a time-reversal filter derived from the measured data and a combined beam pattern was formed. Time-reversal filters that steer the beam were also generated and it was found that sidelobe level worsened with larger steer angles. A simple mutual coupling model was proposed to explain the beam pattern feature.