A 500-nW-to-1-mW Input Power Inductive Boost Converter With MPPT for RF Energy Harvesting System

This article discusses a novel RF energy-harvesting system for available power as low as 500 nW. The system includes a main RF rectenna (antenna followed by rectifier) for energy harvesting, an auxiliary RF rectenna for power detection, and a boost converter along with its control circuit. For maximum power point tracking (MPPT), a particular reference voltage
${V_{\text {ref}}}$
for a range of received RF power (from −11 to 3 dBm) is used to harvest maximum available power from the main rectenna by regulating its output voltage with the help of the boost converter.
${V_{\text {ref}}}$
for MPPT is provided by the auxiliary RF rectenna and the power-detector circuit and depends on the RF power. The complete system is designed, simulated, fabricated, and tested in the 180-nm mixed-mode CMOS technology. Measured results show that the boost converter can track the maximum power point for the input available power ranging from 500 nW to 1 mW. The efficiency of the boost converter is a function of the available input power and the equivalent source resistance of the RF energy harvester. For an equivalent source resistance of
${1~\text {k}\Omega }$
, the maximum efficiency of the boost converter is 91.6% at
${165~\mu \text {W}}$
of the available input power. As a potential application, a
${\Delta \Sigma }$
modulator designed in the 180-nm mixed-mode CMOS technology is powered by the proposed energy-harvesting system. The efficiency of the boost converter is approximately 76.6% while powering the
${\Delta \Sigma }$
modulator and 78.5% while powering the dc load at the RF power of
${-7\,\,\text {dBm}}$
.