| 摘要 |
<p>PURPOSE:To make it possible to exclude radiowave interference between interrogators by setting frequencies so that the difference between the transmitting frequencies of the interrogators is smaller than the value which is obtained by subtracting one half of the bandwidth of a BPF from the data-signal carrier frequency of a responder. CONSTITUTION:When a transmitting frequency F1 is transmitted from an interrogator Q1, a responder A1 modulates the signal with a data frequency fm and transmits the signal. The interrogator Q1 synchronously detects the modulated reflected wave and a source signal from a signal generator 1 in a mixer 5. Then, the detected signal of the frequency fm is made to pass through a BPF 6 having the characteristics of a central frequency fm and a bandwidth 2Bm and taken out of a demodulated signal output terminal 7. At this time, a signal frequency F2 from a neighboring interrogator Q2 is readily mixed into the interrogator Q1, and the frequencies F1 and F2 are mixed in the mixer 5. Thus an interference wave ¦F1 - F2¦ is generated by the beat. In order to remove the wave, the frequencies are set so that ¦F1 - F2¦ < fm - Bm is obtained. This is possible by decreasing the difference between F1 and F2 or by making the data frequency fm higher.</p> |
