In this work, RFID based sensors are introduced, which means very low-cost sensing nodes and loggers utilizing the hardware and protocols of traditional passive RFID transponders and readers for the short distance wireless sensor readout. Classic frequencies bands include LF similar to 125kHz, HF similar to 13.56MHz, and UHF similar to 900MHz. While HF and UHF off-the-shelf ICs and available IP exist to implement sensor transponders, is not the case of LF. In this work, an ASIC is presented to enhance the reading distance of a semi-active LF sensor transponder up to a few meters. The ASIC includes a 134.2kHz-centered band-pass amplifier, a similar to 50ms pulse detector, and a HV H-bridge to drive the antenna coil. It was fabricated in a 0.6 mu m HV-CMOS technology and tested. It was capable to detect the presence of a portable reader, up to a 5m distance, corresponding to an input signal as low as 40 mu V-p in the antenna, with a continuous-time current consumption < 3 mu A.
