Calibratability of Aperture Arrays Using Self-Holography

Calibration of the receive path gains of antenna arrays is normally done using the array covariance matrix, implying a computational load and data volume that scales with the square of the number of receive paths in the array, P. This may become prohibitive for very large arrays and arrays with limited computing resources. Alternatively, self-holography (SH) solves the gains using the correlations between a reference signal and the antenna signals, resulting in a linear scaling with P. The drawback of SH is that it assumes that the reference signal is free of interference. In reality, this will rarely be the case, and the presence of interference will reduce the accuracy of the gain estimates. In this article, we analyze the mathematical model underlying SH, and we extract an analytical expression for the signal-to-interference ratio (SIR) that can be used to relate the accuracy of the gain estimates to the level of interference in the reference signal. We conclude this article by applying SH to three practical examples that are representative of the aforementioned extreme calibration scenarios. The practical results are in line with our theoretical findings, which confirms that we have successfully derived accurate assessment criteria.