Aerospace and Electronic Systems Magazine August 2016 - 25

erating in the LDTP field. Figure 1 schematically shows how the LDTP line works Besides studying the LDTP of radio waves, I was interested in two additional issues: C C the influence of randomness in the antenna aperture on the characteristics of expensive large RA (Figure 2(a)) (note that these issues were considered earlier in the tolerance theory in the beginning and middle of the 1950s. The authors of studies [1] and [2] studied the influence of manufacturing inaccuracies of the RA reflectors on their characteristics. In these studies, errors and their correlation radius were assumed to be small. However, it soon became clear that with the increase in RA and the associated design complications, the operational deformations of RA noticeably increased, and the assumptions of works [1], [2] became unacceptable); external SAT problems, the essence of which consisted in finding, by given statistics of sources, statistics of the antenna field and associated statistical characteristics. HOW TO APPROACH THE PROBLEM I decided to build the grounds of SAT on an example of the simplest model. As such, I chose a linear continuous antenna with the uniform amplitude distribution and homogeneous, normally distributed phase errors. My effort now turned to outlining the main issues for the new theory to address, developing a procedure for their solution, and the statistics of the diffraction image on a focal plane of a receiving RA (focusing system) when the wave, which passed a certain way in the troposphere, impinges on it (Figure 2(b)). These issues were considered in [3], but their solution was not completed. Physically, these three issues are different, as different as the mechanisms of origin of sources' fluctuations in the antenna aperture. They are united by one thing: in all three cases, the field distribution in the antenna aperture appears to be random. Errors' variance α and spatial correlation radius ρ (shown in Figure 2) can serve as the simplest parameters of the random field. Randomness in the antenna results in randomness in both the field radiated (received) by the antenna and the associated antenna characteristics and parameters. It was impossible to study them using a usual antenna theory, even with some amendments. It became clear to me that these phenomena should be studied with methods used in probability theory and the theory of random functions. A decisive step towards building the "grounds" of a new theory was needed-the theory of antennas with random sources. I called the theory the SAT. Figure 1. Scheme of LDTP line. BUT WHAT DO "GROUNDS" MEAN? It was obvious that issues related with finding statistics of sources' distribution in the antenna (I named them direct internal SAT problems) could not be part of the grounds of this theory, since there were no unified techniques for solving these problems. By analogy with usual antenna theory, we therefore had to consider, as grounds of the new theory, the methods and results for solving the direct AUGUST 2016 Figure 2. Possible mechanisms of fluctuations (errors) of the field in the antenna aperture. IEEE A&E SYSTEMS MAGAZINE 25

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine August 2016