Approaching to embedding thing inquiry manner and the non-contact high-frequency current sensor null

摘要

PROBLEM TO BE SOLVED: To easily identify an underground cavity from another object. ;SOLUTION: A high-frequency signal generator 14 of a sensor 10 outputs a high-frequency signal to a directivity coupler 32 in synchronization with a trigger signal from a control device 56. The directivity coupler 32 divides an input signal into a transmission signal and a reference signal before outputting. A transmission signal is fed to a pair of transmission antennas 16 and 18 via a plurality of power splitters. The transmission antennas 16 and 18 are arranged close to the ground, and current flows into the ground when a high-frequency signal is applied. Antennas 20 and 22 are arranged between the transmission antennas 16 and 18, detects the voltage drop between the transmission antennas 16 and 18, and transmits a reception signal to a mixer 36 via a power combiner 50. The mixer 36 adds a reference signal from the directivity coupler 32 to the reception signal for synthesizing an IF signal and transmits it to the control device 56 via an IF amplifier/filter 54.;COPYRIGHT: (C)2000,JPO