Commit d098415f authored by Tran Huy Vu's avatar Tran Huy Vu

Section 4 figure 4a, 4b

parent afc19578
......@@ -35,13 +35,13 @@
\frame{\includegraphics[scale=0.35]{board.pdf}}
\caption[]%
{{\small Wearable Implementation}}
\label{fig:wearablediagram}
\label{fig:pcbboard}
\end{subfigure}
\caption{(a): Block diagram of the wearable device (b): Individual components on a PCB board.}
\label{fig:wearabledevice}
\end{figure*}
We now describe the design of our RF energy harvesting based wearable device, which includes an accelerometer sensor that can be used to track an individual's movement and gestures. Figure~\ref{fig:diagram} illustrates the overall component-level design of the wearable device, which contains a few key components: (a) an RF-energy harvester, a low-power microcontroller, the low-power accelerometer sensor, a wireless communication interface, a supercapacitor (to provide transient energy storage) and a power management module. Figure~\ref{fig:pcbboard} shows the eventual implementation on a PCB board.
We now describe the design of our RF energy harvesting based wearable device, which includes an accelerometer sensor that can be used to track an individual's movement and gestures. Figure~\ref{fig:wearablediagram} illustrates the overall component-level design of the wearable device, which contains a few key components: (a) an RF-energy harvester, a low-power microcontroller, the low-power accelerometer sensor, a wireless communication interface, a supercapacitor (to provide transient energy storage) and a power management module. Figure~\ref{fig:pcbboard} shows the eventual implementation on a PCB board.
\subsection{The RF Energy Harvester}
The RF harvester works by converting the received wireless transmissions into an output voltage. However, the output voltage usually fluctuates significantly with slight movement in the wearable device. As a result, the instantaneous power of the harvester is not strong and stable enough to operate the wearable directly. We use a boost converter, BQ25570, which stores low voltage energy and boost it into a higher voltage for common electronic devices. This converter has been commonly used in prior energy harvesting applications. It converts input voltage as low as 100mV to a programmable output voltage. (In our implementation, we set the output voltage at 2.57V) This output voltage is then used to operate an entire embedded system including 1 microcontroller, 1 inertial sensor and 1 RF communication front end.
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