Abstract: A road void search radar system includes a rotary encoder, a radar controller, an analyzer, and a recording unit. The rotary encoder generates a pulse signal having a period corresponding to a predetermined distance interval traveled by a vehicle. The radar controller outputs a wave every time the pulse signal is supplied from the rotary encoder. The analyzer analyzes an underground state by processing the output signal received from the radar controller. The recording unit records digital data signals and analyzes results.

Abstract: Subsurface target identification radar includes an antenna array, a rotary encoder, a radar controller, a polarization switching circuit, and transmitter and receiver circuits. The antenna array is constituted by dipole antennas having plane triangle elements. The antennas are disposed at angular intervals of 120.degree. with respect to a rotated symmetric point of the array. The rotary encoder generates a distance pulse every time the radar travels a presetted distance. The radar controller sequentially generates three switching pulses within one period on the basis of the distance pulse from the rotary encoder. The polarization switching circuit selects an arbitrary dipole antenna as a transmitting antenna from the antenna array, selects an arbitrary dipole antenna, other than the selected antenna, as a receiving antenna, and changes a combination of selected antennas every time the switching pulse is generated by the radar controller.