Digital demodulator at low sampling frequency for contactless smart cards transceiver

Smart card applications are very widespread today. The adaptation of contactless technology to smart cards suppresses expensive systems with electric contacts. However, the missing of an embedded power source leads to the use of simple and low power circuits. The chip's supply is obtained by tele-supply. Communication from the contactless smart card to the reader can be performed by load modulation. The information signal detected by the reader is an amplitude modulated signal. The modulation index is low - close to a few percent. Classic analog demodulators need amplification steps matched at the carrier frequency. This article presents a complete digital architecture for the reader system in order to suppress most of the analog drawbacks.