Highly Efficient HEMT Rectifier with a Wide Dynamic Range Based on a Hybrid Coupler for Wireless Power Transfer

In this work, a HEMT-based rectifier with a hybrid coupler is proposed, which exhibits a wide dynamic range of input power. The rectifier is composed of two parts: a main-branch rectifier using two High-electron-mobility transistors (HEMT) for the high input power range, and a sub-branch rectifier using a Schottky diode for the low power range. When the input power falls below the dynamic range of the HEMT-based rectifier, the main-branch rectifier connected to the two output ports of the hybrid coupler can suffer from impedance mismatch. As a result, the power will be reflected and redirected to the sub-branch rectifier located at the isolation port. This configuration effectively utilises the high withstand voltage of the HEMTs at high power levels and the high performance of the Schottky diodes at low power levels. Their combination achieves a rectifier with a wide overall dynamic range. A rectifier operating at 0.95 GHz was designed and fabricated to verify the design approach. The proposed rectifier achieved an RF-DC conversion efficiency of over 55% across a wide input power range of 31 dB, from -7 dBm to 24 dBm, and a range of 20 dB for conversion efficiency of over 65%.