An ultra low-voltage low power PSK backscatter modulator for passive UHF RFID tags compatible with C1 G2 EPC standard protocol

Reducing the power consumption of a passive radio frequency identification (RFID) tag is the key in many applications. As the modulator is usually the most power-hungry block in an RFID tag, this paper proposes a power-saving modulator. The proposed modulator uses phase shift keying (PSK) backscatter modulation which allows tag to communicate data from its memory to a reader by PSK modulation. The proposed modulator uses a MOSCAP as a variable impedance and is designed in a new one-inverter structure in compare to the conventional varactor-based modulators designed in two-inverter structure, as this modulator needs just a low voltage swing to drive its MOSCAP. Using MOSCAP as the variable capacitance leads to a low voltage design. Also, the fundamental equations required for determination of the capacitive impedance seen by the antenna is presented. This impedance is the master key in modulator design. The modulator has been designed, simulated and optimized in 0.18 μm CMOS technology. All possible simulation results are presented to approve its compatible operation with C1 G2 EPC global standard. The power consumption of less than 46 nW is achieved in all process corner cases at 0.8 V power supply.