A Four-Band Rectifier With Adaptive Power for Electromagnetic Energy Harvesting

This letter presents a novel adaptive power rectifier operating at four bands to harvest the electromagnetic energy in the low and wide-range power density conditions. The power range of the rectifier is extended by two operation modes controlled adaptively by a FET switch according to the input power level. A cross-shaped match stub connected by a stepped impedance microstrip line is designed to make the rectifier work at four bands. Two cascaded radial open stubs act as a dc-pass filter to block the fundamental frequency wave and the high order harmonics to further improve the RF-DC (radio frequency-direct current) efficiency, and to smooth the output dc power. When the input power level is -10dBm, the measured maximum RF-DC efficiencies are 47.8%, 33.5%, 49.7% and 36.2% at the frequencies of 0.89GHz, 1.27GHz, 2.02GHz and 2.38GHz, respectively. The efficiency is above 30% in every band when the input power is from -12dBm to 12dBm, which shows a wide input power range.