Efficient passive energy harvesters at 950 MHz and 2.45 GHz for 100 μW applications in 65 nm CMOS

Two 2-stage rectifiers are designed at 950 MHz and 2.45 GHz in 65 nm CMOS bulk technology to provide a 100 μW output power under 1 V with 79.9% and 76.6% power conversion efficiency, respectively. A portable and automated design methodology is used here based on foundry models. This methodology is extended to optimize both the cross-coupled and differentialdrive rectifier architectures at UHF by using a derivative-free optimization algorithm. Transistor and capacitance sizing are discussed based on the method results and a simple RC-filter model. A first-order matching network is used to simulate the overall conversion efficiency of an energy-harvesting system using a 50 Ω antenna. For 100 μW output power, minimum input powers of -8.84 dBm and -8.56 dBm are simulated at 950 MHz and 2.45 GHz, respectively. These low power and high-efficiency AC/DC power converters can be used as energy harvesters in RF links to power wearable biomedical devices.