Reply to Comments on “G/T and Noise Figure of Active Array Antennas”

In replying the author states that Smith ["Comments on 'G/T and noise figure of active array antennas,"' IEEE Trans. Antennas Propag., vol. 65, no. 2, pp. 998, Feb. 2017] is correct in pointing out that low-frequency galactic noise from a specific direction is coherent over the array aperture, citing Ellingson’s system [2011] where galactic noise dominates over thermal noise from the ground. Indeed, such coherent noise must be taken into account in the calculation of antenna system temperature. However, this is considered to be a special case, far from the general situation studied by Lee [2011] whose noise model was based on the experience that most radar antennas operate in an environment where external noises from various sources are random in nature by the central limit theorem. Smith appears to have some misunderstanding of the original paper. The author disagrees with his comment that external noise primarily comes in from the main beam. Some clarifications are in order.