Effects of Failure on Phased-Array Radar Systems

Modern phased-array radars are usually complex systems containing many hundreds or thousands of individual controllable, electronically steered, radiating and receiving elements. The usual definitions of system failure or success are given in terms of a discrete threshold of acceptability for a minimum number of operable elements out of the total simultaneously available. The availability, or readiness, of the phased-array radar system must be examined in a different light in order to account for at least the two following effects which are not normally present in conventional systems: 1) the treatment of the outage threshold on probabilistic grounds in order to include the effects of various physical geometries of operable elements in the antenna array for given levels of outage. 2) the branched dependency of a part of the system on other parts, creating a ``tree´´ relationship between failures at different functional echelons. A definition of availability in terms of performance as well as outage is sought, and consideration is given to the problems of keeping phased-array radars continually available in spite of outages. Analytic treatment of these factors is employed wherever possible in modeling a general phased-array radar with reasonable constraints.