Intercepting Beam-Agile Radar

Modern electronically-scanned-array (ESA) radars can switch between beams in a matter of microseconds. This allows great latitude in constructing the beam schedule. From the point of view of an electronic support (ES) receiver, what are the implications? Repeated search tends to make the radar's beam schedule more regular and predictable. Can this be exploited by the receiver to intercept the radar more quickly? What can be done about strongly aperiodic beam schedules? In this paper, we propose two opposing models for a beam-agile radar. One is a periodic model, accounting for radars with a predictable, repetitive search operation. The other is a stochastic model, in which the beam schedule is modelled by a continuous-time Markov chain, accounting for strongly aperiodic radars. Taking the published beam schedule of a hypothetical, agile radar, we conduct numerical experiments under two different assumptions about the ordering of beam dwells in each radar scan. Under the assumption that the dwells are sequentially ordered, we find that the beam schedule appears periodic from the receiver's point of view, to a good approximation. On the other hand, when the radar dwells are randomly shuffled on each scan, the Markov-chain model proves useful in guiding receiver settings.