A 915-MHz Far-Field Energy Harvester With-22-dBm Sensitivity and 3-V Output Voltage Based on Antenna-and-Rectifier Codesign

An ultrasensitive far-field energy harvester based on antenna-and-rectifier codesign is presented in this letter. To eliminate the lossy impedance matching section, a square loop antenna is optimized to directly connect a highly efficient cross-coupled rectifier. The product of the radiation and matching efficiencies is proposed as the optimization metric for such antenna-and-rectifier codesign. The rectifier and the power conditioning circuitry are fabricated in 180-nm CMOS technology, which requires a minimum incident power of 6.2 mu W (-22 dBm). The optimized antenna is implemented on a Rogers substrate with an overall size of 10 cm(2). An LED is used as the load to illustratively indicate the duty-cycled discharging of the energy harvester. A maximum operating distance of 20 m at 4-W Tx effective isotropic radiated power is demonstrated. This energy harvester can be used in remote sensing and Internet-of-Things (IoT) applications.