An HF Passive RFID Tag IC With Low Modulation Index ASK Demodulator

This paper presents a fully integrated high-frequency (HF) radio-frequency identification (RFID) tag chip based on the ISO/IEC 15693 and discusses a series of design techniques, including analog and digital control circuits. In order to get a more coupled power supply, an amplitude shift keying demodulator with very low modulation index is proposed. Moreover, modulator, limiter, and electrostatic discharge circuit are mentioned to make the tag IC work effectively and reliably. Besides, digital control circuit with 2-kbit EEPROM memory is designed to help the tag operate correctly under a very low magnetic field. The proposed RFID tag IC was fabricated using a 0.18-μm 2P6M CMOS technology with an area of 926 μm by 855 μm and a power consumption of less than 120 μA. Data rates of 6.62–52.97 kb/s are supported. The tag can operate under a minimum magnetic field of 0.12 A/m and a minimum modulation index of 2.33% which is far less than 10% required by the RFID standard. Compared with the prior references, the proposed tag IC has better performances especially in the aspect of low modulation index.