Phase Errors in Phased Arrays: Implications on Forward Gain, Pointing Offset, Calibration, and Beamforming

In this paper we show how phase errors between different analogue signal channels of a phased array affects the quality of
the output phased array beam. Specifically we look at the reduction in forward gain of the array beam and the array beam pointing offset as a function of phase errors and array size. We use a combination of simulations made using the aperture array simulator OSKAR, developed at the University of Oxford, in conjunction with measured results taken from 2-PAD; a functioning, astronomical, dual-polarisation, digital beamforming, 4 × 4 element, aperture array prototype (Greenwood 2007) for the Square Kilometre Array (Taylor 2007) developed by a consortium of UK universities. We show that phase errors between different signal channels is specifically an important issue for broadband arrays like 2-PAD, and comment on the relative benefit of digital beamforming versus analogue beamforming engines.