| 摘要 |
PROBLEM TO BE SOLVED: To obtain a modulator which has superior linearity and a high ON/ OFF ratio by receiving and amplifying the output of a 1st band-pass filter up to a specific level, receiving the reception output from a receiving antenna and performing low-noise amplification to remove unnecessary component, receiving the output of a 2nd band-pass filter and generating an intermediate- frequency signal, and receiving and distributing the output of a sender. SOLUTION: The ASK modulated signal outputted from an even higher harmonic mixer 37 for transmission after having unnecessary waves removed by the 1st band-pass filter 12 is amplified by a high-output amplifier 13 up to the specific level and sent from a transmitting antenna 14. The BPSK modulated wave sent from an on-vehicle device is received by a receiving antenna 15 on a roadside machine side and a low-noise amplifier 16 performs low-noise amplification. The output signal of the low-noise amplifier 16 has its band limited by the 2nd band-pass filter 17 and is inputted to the RF terminal of an even higher harmonic mixer 38 for reception. The carrier from a power distributor 24 is inputted to the LO terminal of the even higher harmonic mixer 38 for reception.
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