The problem of active control for both the magnitude and spatial distribution of individual components of the interference component of the Poynting vector within the near zone of a system of radiators is studied. The characteristic size of this zone is on the order of the wavelength and is characterized by the presence of evanescent (nonpropagating) fields, which are formed due to the interference interaction of radiators. Using multipole expansions for fields and special summation formulas for such expansions allows one to obtain concise expressions convenient in carrying out numerical calculations. The results of calculations confirm the feasibility of the above-mentioned control in principle in solving problems of medium and object sensing.At the present time, the application area of nearfield microscopy, especially with the use of optical and infrared radiation, has been considerably expanded [1]. The possibility of breaking the diffraction limit was clearly experimentally shown for the first time in the microwave band [2]. This possibility was efficiently used, in particular, in problems of near-field microwave diagnostics of biological media [3]. At the same time, the results of some works (e.g., [4]) testify to the appropriateness of applying the technology in problems of radio tomography [5] with the use of evanescent (attenuating) fields of systems of identical radiators.The dynamics of total and interference energy flows in near fields of such systems was studied in part in [6]. Simultaneously, the presence of a nonradiative energy transfer between radiators and an additional increase or decrease in the radiation power were revealed. However, an important aspect related to the meaningful control in the near zone of a system of radiators by individual components of the real part of the interference component of the complex Poynting vector has not been studied. This topic is discussed in this work.The simplest model of a system of identical radiators is a pair of collinear electric dipoles with moments and (Fig. 1a).In a system of spherical coordinates connected in a conventional manner with Cartesian coordinates , components of their fields can be represented [7] in the form of the following expressions (under the assumption that the time dependence has the form ):(1)where is the imaginary unit, is the wavenumber, is the wave resistance of the ambient medium, are spherical Bessel and Hankel funcint S 1 p 2 p , , r θ ϕ , , x y z exp( ) i t ω ( ) ( ) ( ) ( ) ( ) ( ) ( ) [ ] ( ) ( ) ( ) (1) 1 0

The problem of active controlling of the structure of fields of combined radiating systems within their near zone is studied. The characteristic size of this zone is on the order of the wavelength and is characterized by the presence of evanescent (nonpropagating) fields, which are formed, among other things, due to the interference interaction of radiators of the system. Using multipole expansions for fields and special summation formulas for such expansions allows one to obtain concise expressions convenient in carrying out numerical calculations. The results of calculations confirm that the evanescent fields' structure plays a significant part in the process of the formation of the radiation field.

We describe the operation of a simple near-field interference microwave microscope. The microscope contains two identical probes which are connected to the ends of segments of the coaxial transmission line. The probes are constructed from an open-ended conical coaxial line and are excited by applied microwave voltage in the frequency range of 0.6 – 7.0 GHz. The computer simulation of the field distribution near the aperture of a separate probe was performed. The test objects are placed in the gap between the probes apertures. The main attention was concentrated on motor fuels to detect other impurities. In particular, diesel fuel was studied with impurities in the form of kerosene and synthetic motor oil in different proportions. It is shown that the microscope can reliably detect these impurities even if their content is relatively small. It was also demonstrated that the microscope can be used for determination of the alcohol quality and spirit-based solutions.