| 摘要 |
<p>PURPOSE:To detect an underground obstruction from a distant place by driving a transmitting antennas with the frequency containing the signal, whose half wavelength is the diameter of a cutter head in the reverse phase, generating the standing wave in the cutter head, and obtaining the result equivalent to the radio wave in low frequency. CONSTITUTION:Transmitting antennas 2 and 3 are provided at the front peripheral part of a cutter head 1, and receiving antennas 4 and 5 are provided in the orthogonal direction with the transmitting antennas. A transmitting circuit 11 supplies the signal in the frequency band, wherein the frequency whose half wavelength is the diameter of the cutter head at the vicinity of the center, e.g. the signal of 10-100MHz, into the transmitting antennas 2 and 3 through a rotary joint 8 and a 180 deg. hybrid circuit 7. The metallic cutter head 1 is resonated at the frequency of about 30MHz, whose half wavelength is the diameter of the cutting head, and the standing wave is generated. The reflected wave having the resonated frequency component of about 30MHz is received with the receiving antennas 4 and 5. Therefore, the result equivalent to the low-frequency radio wave having the small attenuation rate is obtained, and the underground obstruction can be detected from the distant place.</p> |
