(A) sampling-based ASK demodulator for HF multi-standard RFID reader

Abstract

A novel sampling-based amplitude shift keying (ASK) demodulator for high frequency (HF) multi-standard radio frequency identification (RFID) reader is proposed. The proposed ASK demodulator consists of a half-wave rectifier, a voltage inverter, a Schmitt trigger for differentiation of signal, another Schmitt trigger for self-generation clock, and a rising edge-triggering D flip-flop. In order to prevent transition time or drop time of the envelope detected signal increasing due to envelope detection of capacitance and resistance, the proposed ASK demodulator differentiates data state of the received response signal by using hysteresis range of the Schmitt trigger for signal, without envelope detection. A required clock for edge-triggering of the D flip-flop is generated from the received response signal by using another Schmitt trigger for clock. This prevents clock synchronization problem between the differentiated signal and clock for edge-triggering of the D flip-flop. The proposed ASK demodulator is applied to a HF multi-standard RFID transceiver to verify its performance. The proposed transceiver is implemented in a TSMC 0.18 um CMOS technology and measurement results indicate that the proposed ASK demodulator reliably operates.