Patent ID: 9607186
Date: 2017-03-28
CPC Classifications: G06K,H04B

Claim:
1. An RF tag system for conducting radio communications between an RF tag reader and an RF tag using radio waves in VHF band or above, wherein on the RF tag reader side, the RF tag reader sends a tag activating command including RF tag ID code of an RF tag on the other end of communications in ASK modulation mode, and then the RF tag reader sends a CW radio wave at a query carrier frequency fo, and on the RF tag side, the RF tag determines whether the RF tag ID code is matched with ID code of that RF tag, the RF tag analyzes the command for transmission in the ASK modulation mode, and the RF tag superimposes return information on a sub-carrier signal frequency-offset by a frequency fs in the MPSK modulation for transmission of the CW radio wave to reflect the radio wave, the RF tag system characterized in that: in receiving a response signal from the RF tag on the RF tag reader side in transmission of the CW radio wave, an RF tag reader is used, wherein the RF tag reader includes: means for quadrature detection and compensation that directly conducts quadrature detection by the query carrier frequency fo and then corrects detection error; and a generating circuit that samples signals at a frequency 4fs in order to obtain an MPSK demodulated signal from a detection signal.