Ground penetration radar using free-electron maser

We propose an airborne ground penetration radar that detects small buried objects. Earth electrical characteristics are discussed. Radar frequency is considered to penetrate 30 cm into typical ground and bandwidth is selected to achieve 5 cm range resolution in typical ground. A tunable free-electron maser allows adjustment to cope with earth variability. Frequency is selected to provide narrow enough beams so that clutter no longer dominates. The effects of clutter is reduced by beamforming with an array along the wing and by using a synthetic aperture antenna in the flight direction. The wiggler of the free-electron maser is modified to operate at low enough frequencies to provide adequate earth penetration. Pulse shaping or signal chirp provides the bandwidth at the frequency selected. We make an approximate prediction of signal to noise to show feasibility. Finally we discuss post processing to distinguish objects of interest from clutter.