A High-Efficiency RFEH System With Feedback-Free Fast (F³) MPPT Over a Wide Input Range

This paper presents a high-efficiency, wide-input power range ambient Radio Frequency Energy Harvester (RFEH) system, which comprises an adaptive 4-mode impedance matching network (IMN), a single-stage cross-coupled differential-drive (CCDD) rectifier, a maximum power point tracking (MPPT) circuit, and a power manager unit (PMU). To adaptively configure the impedance matching network and modulate the T<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> of the buck-boost converter, a feedback-free fast (F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>) MPPT technique based on the input power detection and parameters direct adjustment is proposed. It can effectively address the trade-off between the speed and accuracy in the impedance matching as well as in the maximum power transmission. Therefore, the power conversion efficiency (PCE) of the proposed RFEH system has been greatly improved. The power manager unit (PMU) is composed of a buck-boost converter, a self-supply unit, and a load regulator, which is employed to implement the F<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> MPPT, startup, and self-powered of the RFEH system. The proposed design is fabricated in a 0.18-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m CMOS technology, and the chip area is about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.52\times 0.78$ </tex-math></inline-formula> mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The measurement results demonstrate that the proposed RFEH system can operate in a wide P<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</sub> range of −23 to 1 dBm with over 96% MPPT accuracy. It achieves PCE >20% in the P<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</sub> range of −17 dBm to 1 dBm, with a peak PCE of 49.4% at P<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {IN}}= -5$ </tex-math></inline-formula> dBm.