SNR improvements in NIITEK ground penetrating RADAR

The spatial resolution and peak signal to average noise ratio of the NIITEK ground penetrating RADAR is shown to be improved by the application of an inverse point spread function operation. Both 1-D and 2-D point spread functions are developed. The 1-D inverse PSF is developed from the step discontinuity in impedance due to the air/ground interface. The 2-D inverse PSF is developed from an image of a small sphere in air. The sequential application of the two inverse PSFs using convolution in the spatial domain compensates for two distinctly different effects. The 1-D blurring is due to AC coupling of the RADAR which produces a bipolar derivative of the narrow RADAR pulse. This is replaced by a single pulse in range which represents the location of an impedance discontinuity. The 2-D blurring is due to the wide beamwidth of the adjacent channels of the 24 channel linear array and the operation in the near field of the antenna which causes the characteristic parabolic scattering of a point signal due to adjacent channel crosstalk. Over a set of 32 landmines at a government test site an average improvement in peak signal to RMS noise ratio of 7.19 dB for 1-D only inverse filtering is realized. When 1-D processing is combined with 2-D inverse filtering, an average SNR improvement of 7.68 is realized with significant spatial resolution improvement. Subsequent processing with a moving average filter of size 2 and 4 in depth yields 8.14 and 9.88 dB net SNR improvement respectively.