| 摘要 |
Provided is a reader/writer which can identify an arrangement order of RFID tags and the movement direction with respect to an antenna. This reader/writer 50 is configured to include a PLL circuit 1, a VCO 2, a modulator 3, a circulator 5, an antenna 6, a mixer 9, a mixer 11, a BPF 12, a BPF 13, an A/D converter 14 and a calculator 15. The PLL circuit 1 synchronizes the phase of an output signal of the VCO 2 with the phase of a reference input signal. The VCO 2 oscillates at a predetermined frequency based on a control voltage of the PLL circuit 1. The modulator 3 modulates a signal sent from the VCO 2 to a microwave. The circulator 5 sets its direction based on the direction of the microwave. The antenna 6 sends a microwave, and receives a reflected wave from a tag 7. The mixer 9 demodulates a sine wave, while the mixer 11 demodulates a cosine wave. The BPF 12 allows only a predetermined frequency component of a signal of the mixer 9 to pass therethrough, while the BPF 13 allows only a predetermined frequency component of a signal of the mixer 11 to pass therethrough. The calculator 15 calculates the phase based on the A/D converter 14 and an A/D converter 16. |
