## 4 Results
#### 4.3.1 Rectifier Systems and Their RF Energy Harvesting Efficiency
* Single-step In contrast, single-step rectifiers offer a simpler and more compact solution. Although they typically exhibit lower efficiency compared to their multi-step counterparts, their straightforward design and reduced component count make them well suited for low-cost, low-power applications. These rectifiers are often used in devices with minimal power requirements and space constraints, such as sensors in IoT networks, as detailed in Table 19.
* Full-wave Full-wave rectifiers, rectifying both halves of an alternating current (AC) signal, offer improved efficiency and reduced ripple compared to half-wave designs. This makes them ideal for applications requiring stable, consistent DC output, such as battery charging \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** & \begin{tabular}{c} **Output Power or** \\ **Voltage** \\ \end{tabular} & \begin{tabular}{c} **Gain in** \\ **(dBm)** \\ \end{tabular} & \
\begin{tabular}{c} **Efficiency** \\ **(\%)** \\ \end{tabular} &
\begin{tabular}{c} **Matching Network** \\ \end{tabular} \\ \hline
[60] & — & — & — & — \\ \hline
[82] & \(>\)0.5 V & 6 & 52.6 & Shunted and shorted stubs and transmission line \\ \hline
[31] & 0.5, 5.4 V & — & 22, 54 & PI-matching and L-matching network \\ \hline
[32] & 2.9 V & 10 & 74 & — \\ \hline
[33] & 2 V, 3 mW & 8 & 72.9 & Short RF chip capacitor and coplanar line with super-strip lines \\ \hline
[34] & 1.8-3.3 V, 100 \(\mu\)W & \(<\)\(-\)15 & 21 & Cascaded impedance-matching circuit with load stages \\ \hline
[36] & 28 \(\mu\)W & \(-\)20 & 45 & — \\ \hline
[39] & — & \(-\)10 & 80 & ELC resonator array \\ \hline
[43] & 0.8 V & \(-\)5 & 50-60 & — \\ \hline
[44] & 3.3, 4.52 V & 5 & 79, 86 & Shunted stub and microstrip lines \\ \hline
[47] & 2.85 V, 172 \(\mu\)W & — & 22.5 & — \\ \hline
[48] & 366 mV & \(-\)7 & 45 & Parallel inductors and transmission line \\ \hline
[51] & 4 V & 0 & 60 & — \\ \hline
[52] & 1.8078 V & 13 & 59.9 & Matching microstrip line, a \(\lambda/4\) microstrip line \\ \hline
[55] & 0.2 V & \(\approx\)\(-\)20 & 40 & — \\ \hline
[58] & \(<\)60 mV & 9 & 50 & Inductive coupling \\ \hline
[61] & — & — & 59.5 & L-slot matching circuit \\ \hline
[63] & 1 V & 60 & 3 & PI-section matching circuit \\ \hline
[67] & 2.1 V & \(-\)9.8 & 65.7 & T-shape dual-band matching network \\ \hline
[75] & 0.7 V & — & 65 & Dual-branch configuration for impedance matching \\ \hline
[76] & 1.71 V & \(-\)3 & 73.4 & Complementary LC resonant structure for impedance matching \\ \hline
[78] & 330 mV, 15 \(\mu\)W & \(-\)20 to 0 & 40 & Two-stage impedance matching \\ \hline
[81] & 788 mV & \(-\)15 & 73.88 & LC circuit for impedance matching \\ \hline
[87] & — & 10 & — & — \\ \hline
[91] & 3.7 V & 14 & — & — \\ \hline
[92] & 5.6, 7.3 V & \(-\)30 & 77 & — \\ \hline
[93] & 1 V & 23 & 41.8 & Compact inductive coupling \\ \hline
[94] & 298 mV & 5 & 54 & — \\ \hline
[95] & 0.94 V & 25 & 35.5 & Multiband matching with radial stubs \\ \hline
[100] & 168.3 mV & \(-\)5 & 52 & — \\ \hline
[103] & 0.94 V & 2 & 60 & Impedance-matching circuit \\ \hline
[107] & 1.46 V & \(-\)6.9 & 70.5 & Wilkinson power divider and a hybrid coupler \\ \hline \hline \end{tabular}
\end{table} 
Table 17: Constructive characteristics of rectifiers within Schottky classification. These include the coupling network, efficiency, and power or voltage generated by the rectifier. systems or larger energy harvesting setups. Their superior performance ensures reliable operation even in demanding environments, as illustrated in Table 20.