A pulse radar front-end using an NRD-guide technology was fabricated for level sensing system at millimeter wave lengths, and range finding was performed by using it. Multi-reflection however occurred between a target and a planar antenna due to a pencil beam radiation of our-developing planar antenna, so that precise distance estimation could not be performed for short range detection. To overcome such difficulty, we developed an FPGA-based signal processor to eliminate such multi-reflection and to detect distances of multi-layered targets.