| 摘要 |
<p>PROBLEM TO BE SOLVED: To use an inexpensive cable and to eliminate the need of an amplifier whose gain is large by connecting an antenna module having plural high frequency circuits and antennas with a main body part having plural signal processing circuits by a cable. SOLUTION: When an ASK modulation wave is transmitted from the antenna of an ETC transmission/reception terminal station installed in a tollgate to a vehicle entering the tollgate, the ASK modulation wave is received by an antenna 4 connected to an on-vehicle transmitter/receiver for ETC loaded on a vehicle. The signal received by the antenna 4 is amplified by a low noise amplifier 10 through a transmission/reception switch 5 and is mixed with an oscillation signal that an oscillator 16 outputs in a mixer 11. Then, it becomes the intermediate wave signal of 40 MHz. The intermediate wave signal is envelope-detected and becomes a demodulation signal by a detection diode 12. It is inputted to a demodulation signal amplifier 13. The demodulation signal amplifier 13 inputs the amplified demodulation signal to a reception signal processing circuit 22 and inputs a CD signal showing that the ASK signal wave is received to the reception signal processing circuit 22.</p> |
