The specific of 3D passive radars sensing alive and non-alive objects

Usually, two coordinates of the object only can be measured by passive radar, like the direction to the object or two Cartesian coordinates of the object. This is the 2D location. However, when sensing an object in the some environment, for example, inside the human body, or when sensing underground objects with multispectral passive radar, it is possible to determine the third coordinate - the depth of the object. This is the case of 3D location. This article is devoted to consideration of features of 3D location by passive radars for alive and non-alive objects. For alive objects, it is medical multichannel multifrequency radiothermography, which is used, in particular, to determine the location of a malignant tumor. For non-living objects, it is remote sensing of the earth to determine surface temperature, integral humidity and depth of water table. The models for the description of the reception processes of the own human radio-thermal field are resulted. The possibility of calculating the required parameters by measuring antenna temperatures simultaneously in two different frequency ranges is analyzed. The conditions for solutions finding by both analytical and numerical methods are revealed. The possible maximum depth for tumors detection depending on the parameters of radiothermograph and thermal contrast in the source is determined. The necessitate of multi frequency receiving is approving. Analytical solutions for tumor depth and temperature for the current model are presented.