Overcoming the efficiency limitation of low microwave power harvesting with backward tunnel diodes

This paper explores, for the first time, the use of high responsivity heterostructure backward tunnel diodes to enhance the conversion efficiency of ambient microwave power harvesters. Progress in advancing the performance of low power rectifiers has been slowed because the maximum possible efficiency using Schottky diodes has been reached. Measurements of RF-to-DC conversion efficiency at -40dBm/2.4GHz are reported in this paper, showing that the backward diode outperforms the HSMS-285B Schottky diode by a factor of 10.5 and the Skyworks SMS 7630 by a factor of 5.5. A narrowband rectifier circuit was designed, fabricated and tested, showing a total efficiency of 3.8% for a 100nW input RF power and 18.2% at 1μW input RF power, at 2.35GHz.