V.V. Razevig, A.S. Bugaev, S.I. Ivashov, I.A. Vasiliev, A.V. Zhuravlev
A family of holographic subsurface radars, named RASCAN, has been produced during more than fifteen years. This radar system is based on classical principles of radar technology. Monochromatic signal is emitted into the subsurface, and reflected by heterogeneities with dielectric constant different from the medium. The reflected signal is received by the radar antenna, amplified, processed, and displayed on a computer screen. Images are recorded by line-by-line sweeping the antenna across an investigated surface.
The principle of image formation in holographic radar is the same as in the optical holography. The receiver of the device registers the interference pattern (or hologram) caused by mixture of the reference and scattered waves. Until recently RASCAN radar had the direct-gain receiver that registered only amplitude of reflected signal. It reduced quality of images reconstructed from amplitude holograms.
This year the new generation of RASCAN radars with quadrature receiver have been developed at Bauman Moscow State Technical University. This technique allows to record the amplitude and phase of reflected signal. The Fourier-based computer algorithm is used for the reconstruction of the recorded holograms.
The results of computer simulation and laboratory experiments show effectiveness of image reconstruction algorithm. The images obtained by new device have appreciably better quality, than by old one. In contrast to optical holography the reconstruction algorithm produces not the direct shape of object but its reflectivity function. In most cases the form of this function allows to easily recognize the object.