A. G. Shubov

Focusing electromagnetic field in a Fresnel zone is the problem connected with concentration of microwave radiation power in a limited area of space. Such problem arises, in particular, in systems of Wireless Power Transmission by means of microwave beam (WPT) from remote sources of radiation to rectenna which transforms a microwave energy to a direct current (DC). For effective WPT with small losses it is required usually to create a taper amplitude field distribution (AD) of Gauss form in the transmission antenna aperture whereas a phase distribution (PD) provides a summation of the fields radiated by all elements of the transmission antenna in focus. Phased array antennas (PAA) can be used for this purpose. To create a smooth distribution of the field in the aperture of the PAA consisting separate subarrays it is necessary to apply multi-type modules. An application of the single-type modules allows to lower system cost essentially. However the single-type unified modules with uniform amplitude excitation in their limits lead to formation of step AD in the aperture of the PAA as a whole. Such AD decreases the WPT efficiency because grating lobes arise in this case. In addition, radio noises appear for other systems. Simulation of modular focusing PAA characteristics is performed for WPT application. The planar array with the square aperture and square grid of element arrangement is considered for several variants. PAA with smooth Gauss amplitude distribution (AD) of the field in the aperture is accepted as an initial model. The square-law phase distribution (PD) takes place in this case. Characteristics of PAA with the same PD when the amplitude of the field is a constant within each unified module and in case when АD within each module is non-uniform (the last version is typical for modules with quasi-optical excitation) are estimated also. Characteristics of modular PAA are defined in the plane of focusing and behind it. It is shown that step AD under square-law PD does not lead to essential decrease of transmission coefficient between PAA and rectenna when the sizes of the PAA at least on one or two orders exceed the sizes of modules, and non-uniform amplitude distribution within each module is in limits (2 - 3) dB. Step character simultaneously both AD and PD, causes appreciable increase of grating lobes. Parameters of modular focusing PAA under scanning are estimated. Examples of concrete application of modular PAA for WPT between two satellites are given.