A 920 MHz band rectenna with the impedance transfomed small loop antenna (IT-SLA)

In this paper, an impedance transformed small loop antenna (IT-SLA) for $\text{k}\Omega$-class antenna impedance is proposed for the 920 MHz band rectenna in sub-mW operations. Conventional small loop antennas (SLAs) with $\text{k}\Omega$-class antenna impedance have extremely larger size than SLAs with over-20 $\text{k}\Omega$ impedance. For reduction of the antenna size, the novel IT-SLA is configurated with the SLA and two additional series capacitors that behave as the impedance transformer with rectifier’s input-capacitance. In 920 MHz band, the proposed IT-SLA achieved a physical size of 34% compared with the conventional SLA with 4 k$\Omega$ impedance. The measured rectification efficiency of34% at the received power of 0.1 mW is obtained in the 920MHz band rectenna with the IT-SLA.