Integracja radaru wizualizacji podpowierzchniowej (GPR) z użyciem technologii FPGA

Radar wizualizacji podpowierzchniowej służy do zobrazowania struktur niedostępnych dla wzroku ludzkiego (geologia, budownictwo, archeologia, wykrywanie min bojowych itp.). Integracja radaru narzuca szczególne cechy techniczne komponentów składowych (np. różnorodność i precyzja czasowa sygnałów). Technologia FPGA doskonale spełnia te wymagania, oferując możliwość generowania wysokorozdzielczych czasowo sygnałów, budowania transmisji danych oraz wykonywania zadań cyfrowego przetwarzania sygnałów.

Ground penetrating radar (GPR) takes many different forms according to the specific application area (geology, architecture, archeology, mine detection, etc.). But the general idea is always the same; some RF/microwave spectrum is transmitted and its reflections from objects are received and converted to a computer image. It looks quite similar to the airborne radar concept, except: observed objects are rather small, being nearby to the antenna system and located underground. To observe small objects, a wide bandwidth is needed, of a few GHz usually. When objects are near the antenna system it is hardly possible to use gating in order to eliminate multi reflections. The near field geometry directly influences image reconstruction algorithms. The surface of the ground (or other material) separates in fact two dielectrics with quite different electrical properties, internal inhomogeneity is typical for a soil; strong surface reflections and clutter appear. GPR is one of the most difficult radar to build. Its antenna system is extremely difficult to construct. The bandwidth has to be the ultra wideband (UWB) kind. The electronics has to synthesize and acquire high frequency radio signals. In this work an experimental GPR is presented, with attention paid to the use of FPGA technology as a bloodstream of the system. The FPGA is able to generate high resolution in time control signals, form transmission data paths and allows implementation of high speed digital signal processing tasks.