| 摘要 |
PURPOSE:To enable the investigation even to an insulated object or an underground object, by radiating an FM-modulated high frequency carrier wave from the ground surface into the ground and receiving a reflected wave from the underground object with FM modulation. CONSTITUTION:An electric wave is radiated through a transmitting antenna 6 and reflected by an embedded underground object 7 to be received at a receiving antenna 8. A period decided by the frequency passing through a voltage control band pass filter 13 approximately coincides with the time during which the electric wave has a round of a feedback loop of an amplifier 9, an FM demodulator 10, a variable gain amplifier 11, the filter 13, an FM modulator 2 and an amplifier 3. As a result, the oscillation is generated at the above-mentioned feedback loop. Thus the electric wave delivered through the antenna 6 is modulated by the oscillating frequency generated within the feedback loop. The depth of the object 7 can be estimated from the oscillating frequency. |
