Low Power RF Interface of the Near-field Communications Tag IC for Sensors

—In this paper, we propose the RF interface of NFC tag IC which is necessary for transmitting the results obtained using blood glucose sensor, water quality sensor, gas sensor and radioactive sensor to portable devices such as mobile phones. The proposed RF interface complies with the ISO14443 type-A standard using 100% ASK and solves the power and clock generation difficulties by using the internal V_TH canceling rectifier that is based on the high efficiency voltage doubler and the switching phase locked loop. In the measurement results, the internal V_TH canceling rectifier in the RF interface shows more than 80% power efficiency from 100% ASK signal, and successfully generates 1.8 V / 2.5 V supply from the input signal power higher than 6 dBm through low loss voltage regulator. Additionally, we can verify that the proposed switching phase locked loop is locked at 8 dBm or higher input signal power and successfully demodulates ASK input signal.