| 摘要 |
<p>PURPOSE:To eliminate the need for preparing any special amplifier nor A/D converter at the reception side despite the high frequency of the transmission side by preparing a local transmitter, a frequency mixer and a filter at the transmission side and before an A/D converter or a detector. CONSTITUTION:At the side of a reception circuit, a local transmitter 21 is prepared to transmit a signal of frequency f2 so as to set ¦f1-f2¦ at 20-100kHz with reception frequency f1, together with a frequency mixer 20 which mixes the voltage signal received from the transmitter 21 with the reception voltage signal and divides them into the frequency signals of f1-f2 and f1+f2, and a filter 22 which extracts the signal f1-f2. Then the amplified signal is mixed with the signal of f2 received from the transmitter 21 by the mixer 20, and only the signal of f1-f2 is extracted by the filter 22. This extracted beat-down signal is amplified by an intermediate frequency amplifier 23 and detected to undergo the digital conversion by an A/D converter 6' and then to undergo the coordinate arithmetic processing.</p> |
