## 4 Results
#### 4.3.2 Correlation Between Rectifiers and Performance Metrics  
As part of the response to the third research question, this subsection explores the correlation between rectifier topologies and key performance metrics in RF energy harvesting systems. Given that the rectifier stage is responsible for converting captured RF signal into usable DC power, its design has a direct impact on system efficiency and \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** &
\begin{tabular}{c} **Output Power** \\ **or Voltage** \\ \end{tabular} & **Gain in (dBm)** & **Efficiency (\%)** & **Matching Network** \\ \hline
[69] & \(\approx\) 270 mV & \(-\)3 and 0 & 49 & Frequency divider with impedance coupling network \\ \hline
[84] & 6.27 mW & 9 & 78.9 & Open stub to impedance matching circuit \\ \hline
[106] & 420 mV, 28.75 uW & \(\approx\) 64 & 28.75 & T-matching topology \\ \hline \hline \end{tabular}
\end{table} 
Table 21: Constructive characteristics of rectifiers within the half-wave classification. These include the coupling network, efficiency, and power or voltage generated by the rectifier. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** &
\begin{tabular}{c} **Output Power** \\ **or Voltage** \\ \end{tabular} & **Gain in (dBm)** & **Efficiency (\%)** & **Matching Network** \\ \hline
[56] & — & 20 & 81.2 & Split-ring resonators (SRR) and metallic strips \\ \hline
[62] & 900 mV, 150 uW & \(-\)20 & 68 & Matching networks \\ \hline
[64] & 172 mV, 65 uW & 27.5 & 58 & — \\ \hline
[65] & 17.5 mV & \(-\)20 to \(-\)10 & 91 &
\begin{tabular}{c} T-stub in metamaterial, exponential wave \\ coplanar transmission line \\ \end{tabular} \\ \hline
[71] & 1.43 V & \(-\)2.5 and \(-\)1 & 64 & Double-stub matching network \\ \hline
[86] & 1.8 V & 21 & 63.5 & — \\ \hline \hline \end{tabular}
\end{table} 
Table 20: Constructive characteristics of rectifiers within the full-wave classification. These include the coupling network, efficiency, and power or voltage generated by the rectifier. functional performance. To assess this influence, statistical analyses were conducted to examine how different rectifier types relate to four critical variables: antenna surface area, radiation efficiency, operating frequency, and gain. By uncovering these relationships, the analysis provides valuable insight into how rectifier selection can be optimized in conjunction with overall system architecture to enhance energy conversion capabilities in practical applications. * Area vs. rectifier  
Figure 20 presents the distribution of antenna surface area associated with different rectifier types, revealing notable variability that reflects design trade-offs and application-specific constraints. Multi-step rectifiers exhibit a median area of approximately 2000 mm\({}^{2}\), with a relatively narrow distribution and high outliers. This suggests moderate variability and makes them suitable for systems requiring consistent dimensions with the capacity to support moderate energy collection. Schottky rectifiers, with a mean area near 2500 mm\({}^{2}\), show a wider distribution spanning both low and high extremes, indicating greater flexibility but also the need for adaptable system designs where area may fluctuate depending on implementation. Rectifier-less systems--those where rectifying stage is either external or unspecified-- also cluster around a median of 2000 mm\({}^{2}\), with a narrow spread and some high outliers, pointing to generally compact configurations. Single-step rectifiers present a considerably larger median area (\(\approx\)4000 mm\({}^{2}\)) and a wide distribution, suggesting they are best suited for applications demanding higher power collection, although at the cost of increased spatial requirements and variability. Full-wave rectifiers, in contrast, display a lower median area (\(\approx\)1000 mm\({}^{2}\)) with tight distribution and minimal outliers, indicating compact and consistent performance ideal for space-constrained scenarios.