Active radio frequency identification tag

The invention discloses an active radio frequency identification tag and an implementation method thereof. According to the frequency and phase information of a carrier tracked and received by a phase-locked loop, the tag generates a local oscillation signal with the same frequency and phase of the carrier, and data to be sent is modulated onto the local oscillation signal and transmitted to a reader after power amplification. No crystal oscillator needs to be circumscribed to the tag to be used as a reference datum and the reference datum of the tag comes from the carrier received by tag antenna. A power management circuit is arranged in the tag and controls the on-off of the tag, switches sender-receiver modes and manages power consumption. When the tag is in receiving mode, the phase-locked loop tracks the carrier and when the tag is in sending mode, the local oscillation signal maintains the free oscillation of the state of the moment before.