A wide input range energy harvesting system for AM broadcast with capacitor load

A high efficiency, wide input range radio frequency (RF) energy harvesting system with capacitor load is presented, applied for harvesting the energy from amplitude modulation (AM) broadcast. The chip is fabricated in 55 nm complementary metal-oxide-semiconductor (CMOS) technology, and the active chip area is 1.63 mm(2). The number of stages of the rectifier is reconfigurable to improve the power efficiency when the voltage across the capacitor changes during charge accumulation. A dual-path rectifier with the switch in parallel is adopted to extend the input power range of high power efficiency (>20%). Meanwhile, to achieve the high sensitivity, a 4 nA static current-voltage reference supplying for low-power loop controller is also proposed. The measurement results show that the average power efficiency is improved up to 48.7% when the capacitor load is charged from 0 to 2 V and at least 6.3% improvement compared to fixed stages rectifier. The high power efficiency range is improved by 20 dB, while the single-path reconfigurable rectifiers can only maintain the high power conversion efficiency range for a 14-dB range. The measured RF input power sensitivity is -34.2 dBm for a 1 V output voltage.