# High-Efficiency Triple-Band RF-to-DC Rectifier Primary Design for RF Energy-Harvesting Systems
## 3 Results and Discussion
From the results of Figure 10b, we can conclude that the DC output voltage for an RF input power level greater than \(-15\) dBm is above 0.5 V, whereas for an input power of 0 dBm, it is 3.32 V and 3.24 V for the dual- and triple-band rectifier, respectively. Additionally, Figure 11 illustrates the RF-to-DC efficiency versus frequency for various input power levels \(P_{in}\). From the presented curves, we can verify the system's performance in the frequency bands of interest. Figure 11: RF-to-DC efficiency versus frequency for various input power levels (\(P_{in}\)). Figure 10: (**a**) RF-to-DC efficiency vs. input power \(P_{in}\); (**b**) DC output voltage vs. the input power of the dual-band (two-tone signal: 869 MHz and 940 MHz) and the proposed triple-band (three-tone signal: 866 MHz, 948 MHz, and 2.423 GHz) rectifier for \(R_{L}=13\) kOhm (blue solid line: dual-band, green solid line: triple-band). Table 4 lists the comparative results of this work against previous studies that were based on dual-band rectifiers. It is noteworthy that, among the designs, the proposed system exhibits quite satisfactory performance, and it is one of the three circuits that displays the maximum conversion efficiency for an input power signal below 6 dBm (about 4.0 mW). Furthermore, the maximum power conversion efficiency of the dual-band proposed rectifier in a two-tone signal (concurrent) is 85.9% for an input power of 2 dBm and a load of 13 kOhm. Table 5 lists the comparative results of this work against previous studies that were based on triple-band rectifiers. It is noteworthy that, among the designs with the low-cost substrate of FR-4, the proposed system exhibits quite satisfactory performance. Furthermore, it is one of the designs that achieves the maximum conversion efficiency for an input power signal below 4 dBm (about 2.5 mW). Furthermore, the maximum power conversion efficiency of the triple-band proposed rectifier in a three-tone signal (concurrent) is 81.9% for an input power of 2 dBm and an output load of 13 kOhm. This result surpasses the rest of the circuits described in the studies that are included in Table 4. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & **Impedance** & **Schottky** & **Efficiency** & **Input** & **Load** \\  & **Matching** & **Diode** & **@ Frequency** & **(dBm)** & **(kOhm)** \\ \hline
[8] * & multistub & HSMS285C & \
\begin{tabular}{c} 24\% @ 2.1 GHz \\ 18\% @ 2.45 GHz \\ 57.60\% @ 2.45 GHz \\ \end{tabular} & 10.0 & 1.60 \\  & cross- and & &
\begin{tabular}{c} 57.60\% @ 2.45 GHz \\ 33.62\% @ 5.8 GHz \\ 30\% @ 2.45 GHz \\ 28\% @ 5.8 GHz \\ \end{tabular} & 0.0 & \\
[9] * & T-shaped & HSMS2850 & \
\begin{tabular}{c} 33.62\% @ 5.8 GHz \\ 30\% @ 2.45 GHz \\ 28\% @ 5.8 GHz \\ \end{tabular} & 2.00 \\  & &
\begin{tabular}{c} 2.00 \\ 28\% @ 5.8 GHz \\ \end{tabular} & 10.0 & \\  & broadband & & & \\
[10] * & matching & HSMS285X &
\begin{tabular}{c} \(\sim\)68\% @ 975 MHz \\ \(\sim\)55\% @ 1.9 GHz \\ \end{tabular} & \(-\)10.0 & 15.00 \\  & network & & & \\  & open and & & & \\
[11] * & shorted & HSMS2850 &
\begin{tabular}{c} 63\% @ 1.95 GHz \\ 69\% @ 2.5 GHz \\ \end{tabular} & 7.0 & 1.00 \\  & & stubs & & 69\% @ 2.5 GHz & 3.5 & \\  & & \(\lambda\)/4 T-junction & & \\
[12] * & and shorted & HSMS2822, &
\begin{tabular}{c} 66\% @ 915 MHz \\ 58\% @ 2.45 GHz \\ \end{tabular} & \(\sim\)30.0 & 0.62 \\  & & stubs & & & \\
[13] * & microstrip & HSMS2852, &
\begin{tabular}{c} 56.11\% @ 2.67 GHz \\ 57.95\% @ 3.591 GHz \\ 48\% @ 866 MHz \\ 65\% @ 940 MHz \\ \end{tabular} & 6.0 & 2.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparative results of the proposed dual-band rectifier against related work.