S. P. Skobelev - C.Sc. (Eng.), Leading Research Scientist, JSC «Radiofizika» (Moscow); Lecturer, Moscow Institute of Physics and Technology. E-mail: s.p.skobelev@mail.ru

It is known that the reduction of expensive phase shifters or transmit/receive modules number being connected to the inputs of radiators in phased array antennas for providing a specified array gain in a specified narrow scan region can be achieved by using overlapped subarrays which are forming a sector or contour radiation patterns, which width is equal to the width of the scan region. This paper studies the element use efficiency for planar hexagonal arrays of non-overlapped large-aperture radiators. The element use efficiency is determined as a ratio of the theoretical minimum number of array elements to the actual number of array elements. It is shown, that the indicated efficiency corresponding to a uniform distribution over the radiator aperture is considerably lower than that achieved in arrays even with the simplest overlapped subarrays forming sector radiation patterns. However it is detected that if the distribution in the radiator aperture corresponds to shaping a sector pattern, then the element use efficiency of such non-overlapped radiators becomes comparable to that one for the overlapped subarrays. Compared to the case of overlapped subarrays, the indicated approach to reduction of the number of controlled elements based on using non-overlapped subarrays or large-aperture horn or reflector elements with flat-topped radiation patterns has obvious drawbacks. First of all the element aperture efficiency is very low, therefore the array aperture's area is oversized. If the array elements are arranged in a regular square or hexagonal lattice, the array factor grating lobes will be present in the specified region of scan together with the main lobe. However, as it was noted in the Introduction, the grating lobes can be effectively suppressed by means of irregular arrangement as described in numerous publications. With the indicated drawbacks, the approach has also a definite advantage because the required distributions corresponding to shaping the flat-topped radiation patterns are much easier to realize in the non-overlapped subarrays and elements compared to the overlapped subarrays. Moreover, the oversized array aperture area in the described approach gives a smaller beam width and, therefore, an enhanced power resolved by the array antenna.