A 13.56 MHz rectifier with efficiency-improving harmonic-termination circuit for wireless power transmission systems

New efficiency-improving technique applicable for all types of shunt-diode rectifier is presented. The proposed technique using a harmonic-termination circuit improves the efficiency of conventional shunt-diode rectifiers by nearly 10% at 13.56 MHz. The efficiency of a shunt-diode rectifier was analyzed by using Fourier transform and it is concluded that the efficiency loss can be significantly reduced by using a series resonant circuit to terminate the 2nd harmonic component. The series harmonic-termination circuit consists of lumped components, so that the circuit size in MHz band can be smaller compared to a conventional shunt-diode rectifier with a λ/4 stub line technique. In this paper, both theoretical analysis and experimental results are presented. The proposed circuit can be used for high efficiency and compact wireless power receivers to improve efficiency of emerging wireless power transmission or energy harvesting systems.