The design of a monostatic, ultra wide band,VHF, pulse radar for detection of close-in targets
Ground penetrating radar is currently proving itself as an invaluable tool for the prediction of geological structures in the mining environment. Borehole radar is a specific application of this technology, useful in the prediction of the course of rock layers between boreholes ahead of mining. Establishing borehole radar as an industrial tool requires a system that is more userfriendly and easier to deploy than the bi-static radar systems currently available. The development of a monostatic radar system is discussed. It is an ultra wide band, pulse radar system that operates at VHF (10-100 MHz). The system is required to detect reflections from objects 5 m away and further. This translates to a total electromagnetic propagation time of approximately 100 ns or more in the rock medium. The complete design process - from fundamental requirements, through a conceptual design, to a final electronic circuit - is discussed. The design is also built, measured in the laboratory and taken for initial field trails. The following aspects are considered: • Pulse generation by means of an original circuit based on power MOSFETs. • Routing of the transmitted- and received signal between transmitter, receiver and antenna. This is done using a novel, active quasi circulator topology. • Methods of increasing isolation (actively and passively) between transmitter and receiver. • Interfacing with a specific receiver, antenna and data acquisition system.