Improving range of passive RFID tags utilizing energy harvesting and high efficiency class-E oscillators

The operating range of passive RFID tags is maximized by the use of energy harvesting. In this work the use of light energy collected from solar cells sharing the tag antenna area is proposed, providing a source of power used to activate the tag circuitry in addition to the received electromagnetic power from the reader. The solar cell position is optimized using electromagnetic simulation in order to minimize its effect on the tag antenna. The collected DC power is converted to RF power using a high efficiency class-E oscillator and can be fed into the RF tag terminals using a properly designed coupling circuit. The oscillation frequency is selected so that it does not affect the tag back-scatter operation. The proposed oscillator is demonstrated in simulation. The class-E oscillator can be used with other forms of harvesting technologies such as thermoelectric harvesters.