Self-Holography- Slimming Down Calibration of Large Aperture Arrays

The Mid-Frequency Aperture Array (MFAA) of the Square Kilometre Array (SKA) operating in the 450-1450 MHz range is envisaged to have stations (subarrays) with $\sim10^{3}\ {\mathrm {to}}\ \sim10^{4}$ receive paths. Standard calibration procedures are based on the array covariance matrix which, at this scale, becomes extremely computationally expensive. Alternative, computationally cheaper approaches are in development and some have been proven to work. In this paper, we will focus on a method called self-holography, one of these approaches. Previous studies on self-holography showed that a bias in the gain estimates is caused by factors such as signal interference and system noise. In this paper, we investigate the effectiveness of reducing interference using null placement and subsequently reducing the bias on the gain estimates.