System phase calibration of VHF spaced antennas using the echoes of aircraft and incorporating the frequency domain interferometry technique

Using multiple-receiver arrays, the techniques of spaced antennas and spatial domain interferometry have been widely utilized in mesosphere-stratosphere-troposphere (MST) VHF and meteor radars. As these techniques are applied, the phase imbalance between the receiving channels will cause a biased result if it is not considered in the use of phase angles of the radar returns received in different receiving channels. In view of this, many methods have been employed for the phase calibration of receiving channels. In this paper, we propose one more method/procedure for the calibration, in which the commercial airplane flying routinely is used as a radar target. We measure the zenith and azimuth angles of the airplane with a video camera and estimate the range and height of the airplane from observation using the frequency domain interferometry (FDI) technique. Consequently, the track of the airplane in the vicinity of the radar site can be determined. The phase difference between the two radar echoes received by a pair of receiving channels is then predicted in accordance with the track of the airplane. Comparing the predicted phase difference with that observed, the phase imbalance between a pair of receiving channels could be obtained. Tens of cases show consistent results and so verify the reliability of the method. Also shown is the drift of system phase imbalance from season to season, which might be caused by the temperature dependence of antenna system components.