| 摘要 |
A dual PLL(Phase Locked Loop) type RFID(Radio Frequency IDentification) system is provided to minimize interference among RFID readers by using a channel after checking whether the other RFID reader occupies the channel by using a line discriminated into each PLL when the entire frequency band is unfit for an FHSS(Frequency Hopping Spread Spectrum) mode. The first and second PLLs(192,194) respectively generate the first and second reference frequency signal. An RF receiver(120) processes an RFID reception signal with the first reference frequency signal. An RF transmitter(140) processes an RFID transmission signal with the first reference frequency signal. A signal coupler(170) couples the reception signals of a specific band by connecting to an input terminal of the RF receiver. A signal level detector(180) converts the coupled signal by using the second reference frequency signal and checks a power level of the converted signal. A controller(160) moves the band of the reference frequency signal by applying control voltage to the first and second PLLs if the power level received from the signal level detector is over a predetermined value. |
