A simple method for estimation of maximum spurious radiation level from phased array antennas

According to the new ITU regulation on unwanted spurious emissions from radar transmit antenna, it has become compulsory to measure transmit antenna patterns at spurious frequencies. However, the complex nature of phased array antennas, involving a large number of antenna elements with element-by-element phase-control for beam-scanning, usually makes it difficult to measure all the radiation patterns at spurious frequencies. This paper introduces our approach to this problem, where, under the principle of pattern multiplication, the spurious radiation maxima are estimated by the multiplication between calculated array-factors and measured element-factors, both at spurious frequencies. Among those antenna element types we have examined, this paper deals with the case for dipole antenna as the most typical array antenna element.