Abstract
Phased array radars are able to provide highly accurate airplane surveillance and tracking performance if they are properly calibrated. However, the ambient temperature variation and device aging could greatly deteriorate their performance. Currently, performing a calibration over a large-scale phased array with thousands of antennas is time-consuming. To facilitate the process, we propose a fast calibration method for phased arrays with omnidirectional radiation patterns based on the graph coloring theory. This method transforms the calibration problem into a coloring problem that aims at minimizing the number of used colors. By reusing the calibration time slots spatially, more than one omnidirectional antenna can perform calibration simultaneously. The simulation proves this method can prominently reduce total calibration time and recover the radiation pattern from amplitude and phase errors and noise. It is worth noting that the total calibration time consumed by the proposed method remains constant and is negligible compared with other calibration methods.
Highlights
To ensure a radiation pattern meeting the required performance, an active phased array must guarantee amplitude and phase matching among elements [1,2,3,4]
We propose a fast calibration method based on graph coloring theory
We evaluate mutual coupling between two circular patch antennas for different separations (S) in HFSS 15, which validates the assumption in Section 2.1 that the interferences are negligible compared to the calibration signal, given that, it meets the condition of the optimal coloring problem shown in Equation (1)
Summary
To ensure a radiation pattern meeting the required performance, an active phased array must guarantee amplitude and phase matching among elements [1,2,3,4]. Near-field calibration uses a test probe scanning across the array surface to directly measure each antenna’s amplitude and phase errors This method can obtain high-accuracy calibration results. The received signal is compared to a stored reference obtained during factory test to obtain each antenna’s amplitude and phase errors This method is much faster than the near-field calibration. Reference [16] combines the mutual coupling method and the rotating element electric field vector (REV) method [17] to achieve amplitude-only measurement for phased array calibration.
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