USRP Implementation of a Ground Penetrating Radar Using a Combination of Stepped Frequency and OFDM Principles

We present a Software Defined Radio (SDR) implementation of a Ground Penetrating Radar which uses much larger bandwidth than the SDR instantaneous RF bandwidth in order to increase radar resolution. It is based on the Stepped Frequency principle, where the baseband signal is an Orthogonal Frequency Division Multiplexing (OFDM) signal, transmitted in different subbands by modulating the RF stepped frequencies. Using OFDM in each subband provides faster signal transmission and simpler detection. The receive signal-to-noise ratio (SNR) is improved by repeating a number of times the transmit baseband signal before modulating each RF frequency. The random phase discontinuities between the adjacent subbands that appear when the RF frequency is changed, are removed by postprocessing the received signal. Singular value decomposition is used to remove the effects of the direct and the ground reflected waves. We perform field experiments with anti-tank mines buried in the ground. The resulting B-scans provide excellent detection and localization of the buried objects.