Creation of 3-D Object Radio Images Using Multi-Frequency Multi-static Radio-hologram

Abstract

To date, there are a significant number of scientific publications on the general principles of operation and design concept theory of radio holographic image (RHI) objects based on the multi-static radio-holograms (MSRH). The method differs significantly from the previously known methods of classical radio-holograms (CRH). For the CRH method, are used the equidistant fixed two-dimensional or scanning linear antenna arrays (AA), consisting of antenna elements combined for and receiving. Thus, the number of independent samples of the diffracted field is equal to the number of and receiving elements. Unlike the CRG method, a thinned array consisting of separate and distributed and receiving elements across AA can be used to have the MSRH. Spatial samples of electromagnetic field diffracted on the object are made for all possible bi-static pairs transmitting element - receiving element. Thus, the number of independent samples of the field is equal to the product of the number of elements by the number of receiving ones. To test this method on the complex objects was used the FEKO electro-dynamic simulation software, which allows us to perform calculation of the complex amplitude of the field scattered by a real object. In comparison to the phenomenological model, i.e. a set of independent point scatterers (shining points) the offered approach allows us to record not only the phase, but also the amplitude of the scattered field in each receiving point. With CRH and MSRH methods additional improvement in the quality of radio images (RI) for three-dimensional objects is achieved through the use of multi-frequency radiation. With an equal number of independent samples of the field in both examined methods, the same resolution and quality of focused RI (without diffraction artefacts) the MSRH method has significant advantages in the total number of AA elements. So, when using the scanning linear AA the MSRH method gain in the number of elements can be more than by an order of magnitude. For specific configuration and parameters of the MSRH recording system the paper gives examples of multi-frequency MSRH focusing and radio images obtained using the back-projection algorithms for electro-dynamic models of sphere and cube.