| 摘要 |
<p>PURPOSE:To simplify the structure of an interrogator without reducing the sensitivity of a detector by returning modulated carriers with the phase difference 90 deg. from each other from the first and second replying means provided on a responder respectively. CONSTITUTION:When a transponder 2 receives 21 an unmodulated carrier transmitted from an interrogator 1, the first and second modulated signals 23a, 23b set to the level 1 at different timings from each other while the readout data are kept at the level 1 are inputted to the first and second replying circuits 24, 26 from pulse generating circuits 231A, 231B. The circuits 24, 26 modulate the unmodulated carrier with the signals 23a, 23b, and the phase of the modulated carrier of the circuit 26 is delayed by 90 deg. by a phase shifter 25. The modulated carrier are received by the interrogator 1 and mixed 14 with the unmodulated carrier, the envelope is detected 153 by a signal processor 15, and the readout data are recognized. The modulated carriers have the phase difference 90 deg., the mixed detection signal invariably contains pulses with the fixed level or above, thus the readout data can be surely obtained regardless of the change of the distance between the interrogator 1 and the transponder 2.</p> |
