| 摘要 |
<p>PURPOSE:To detect an underground obstruction from distant place by driving a selected transmitting antenna with 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 equivalent result as the radio wave of low frequency. CONSTITUTION:Small holes are formed at the front edge part of a cutter head 1. Antenna sets 2a and 2b, 3a and 3b and 4a and 4b are provided in the holes so that 30 degrees are shifted. A transmitting circuit 11 supplies the signal in the frequency band containing the frequency, whose half wavelength is the diameter of the cutter head 1, at the vicinity of the center, e.g. 10-100MHz, into the antennas 2a and 2b through a rotary joint 8 and a 180 deg. hybrid circuit 7. The metallic cutter head 1 is resonated at the frequency of about 30Hz with the diameter as the half wavelength. Then, the standing wave is generated. The reflected wave of about 30Hz is received with the antennas 3a and 3b. The attenuation rate of the receiving frequency is far lower than the resonance frequency of 300Hz of the antennas 2a and 2b. Therefore, the obstruction at the distant place can be detected.</p> |
