Aerospace and Electronic Systems Magazine August 2016 - 30

Pioneer Award tennas of such dimensions is defined by a measure to which the directivity loss characterized by the multiplier exp(−α) is acceptable. At α of the order of 3...4 and more, some domain of the directivity saturation occurs. At this domain, the increase in antenna dimension L does not influence its mean directivity. For linear antennas, the left bound of the saturation domain is approximately defined by the value . With the increase in α, the saturation domain widens, so it might appear to be unreasonable or impossible in practice to overcome it. In similar cases, one can talk about the limiting antenna length and the saturation directivity. A value of the latter is defined by the relation . In conclusion, note that the supposed contradictions in different relevant works were because their authors considered different parts of curves like those given in Figure 7. The second appendix concerns the problem of building sectionalized receiving antennas, for those cases when initial antenna dimension L is much more than correlation radius ρ of the phase fluctuations of the wave impinging on the antenna [11]. The antenna is divided into N sections with sizes of about r each, and the in-phase composition of signals from the outputs of all the sections is provided with the automatic control method. In the literature, such antennas are named self-focusing [12], [13]. We have shown that building of the system in this way is equivalent to an N-fold increase in the correlation radius of phase fluctuations in the incident wave. The corresponding gain in the mean directivity can be defined from the plot given in the first part of the monograph. In reality, phases of signals from the section outputs will be adjusted with some errors, and this will decrease a gain in the mean directivity. The obtained expression for real takes into account the number of sections N, the incident wave statistics (values of α and ρ), and the variance of errors of phase adjustment. All the aforementioned discussion does not exhaust the contents of monograph [5]. In particular, I omitted here the consideration of the effect of limiting directivity for RAs [2], the issue of the influence of fluctuations of the incident wave on equi-signalzone method accuracy, the issue of the far-field region of an antenna with random APD, etc. SAT EXTENSION After 1970, my work developed in three directions. I tentatively name them scientific, scientific-organizational, and practical. SCIENTIFIC WORK The scientific direction of my work was aimed at the further development of the SAT grounds, removal of the limitations used when developing the theory grounds, and expansion of the area of its applicability. Unlike the stage of theory formation, at which I worked alone, already in the late 1960s, when being Head of the chair, I involved in the work on SAT a number of the chair workers and postgraduate students-later candidates for the Dr.Sci. degree. Leonid G. Kornienko was the most active of them. Later he became Doctor of Technical Sciences, Professor, and coauthor of a number of joint (my and his) publications. Investigations were carried out on a number of the SAT issues: the development of 30 grounds for the statistical synthesis of antennas, a study of statistics of antenna radomes and covers, building the statistical antenna measurements theory, and among others, a study of statistics of large sectionalized TWAs. On some of those issues, the investigations were carried out jointly with workers from major Moscow research institutes, and the results were employed in projects of those institutes and published as nonclassified of classified publications. The important result of all this work was the defenses of theses for candidate degree (equivalent to Ph.D.), and later for the Dr.Sci. degree. Since the middle 1970s, work on one doctoral and three to five candidate dissertations were completed yearly. This work continued at this chair also after I was retired from the Armed Forces in 1980, and unexpectedly for me, in spite of an earlier agreement, I was forced to leave ARTA. At a new place, the Kharkov Institute of Radio Electronics (KhIRE, now Kharkiv National University of Radio Electronics, KhNURE), the scientific situation radically differed from that created by my efforts at the chair of ARTA. At KhIRE, the antenna team consisted of eight workers, of which six researchers had dissertations that failed. A major part of this work was connected with the investigations of nonlinear antenna effects. I had to master this new (for me) scientific area as soon as possible. I succeeded in this rather quickly; and under my leadership, for two or three years, all six theses were improved and successfully defended. What is more, I had radically changed the direction of the investigations, having stated the problem for the antenna team to create a rather general theory of antennas with nonlinear elements (ANE). For a number of years several monographs devoted to this problem were published [14], [15]; and in the early 1990s, the results achieved allowed me to plan to publish a special monograph. This project was supported by the Ministry of Education; later its financial support was approved by IEEE. Unfortunately, due to a short-sighted policy of the KhIRE leadership, this monograph was not published. However, it was a consolation for me that two theses for Dr.Sci. degrees on these issues were produced, which were defended under my supervision. Besides, a central part of the monograph was published later in the Handbook on Antenna Techniques [16] and in a prestigious Russian journal [17]. Along with the work on the ANE theory, I gave 10 lectures on SAT for the chair collective and initiated the investigations on SAT at KhIRE. In this direction, three candidate and one Dr.Sci. theses were defended. In total, for 60 years of my scientific-pedagogical activities, under my supervision, over 20 Dr.Sci. and about 50 candidate theses were defended. I would like to note that some of those theses were fulfilled by researchers from different organizations of the former USSR. Now let me briefly dwell on some SAT results obtained at ARTA and KhNURE. Investigations of the Field Statistics in the Fresnel Region, a Study of the Field Statistics of Focused Systems (jointly with Yury M.Borodavko) Beside the theoretical interest, the investigations in these directions were also stimulated by a number of practically important circumstances. The increase in antenna dimensions (in particular, when using the synthesized aperture antennas), and mastering of shorter and shorter waves lead to an increase in the Fresnel region. Besides, IEEE A&E SYSTEMS MAGAZINE AUGUST 2016

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