## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{1}{c}{**Specifications**} & \multicolumn{5}{c}{**Value**} \\ \hline Frequency operation & & & \multicolumn{4}{c}{915 MHz} \\ Received antenna gain & & & \multicolumn{4}{c}{2 dBi} \\ Transmitted antenna gain & & & \multicolumn{4}{c}{6 dBi} \\ Transmitted power (dBm) & & & \multicolumn{4}{c}{+23 dBm} \\ Distance (m) & 1 & 2 & 3 & 4 & 5 & 6 \\ Received Power (dBm) & 0 & \(-6.72\) & \(-10.3\) & \(-12.7\) & \(-14.7\) & \(-16.3\) \\ Efficiency (\%) & 49 & 42 & 33 & 28 & 25 & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: RF system power link budget. Figure 1: Diagram illustration of Wireless Power Transfer (WPT) concept [4]. Reproduced with permission from [4], Copyright IEEE, 2016. However, all these topologies have noticeable limitations, such as the inability to attain a high efficiency over a wide range of input powers. This is mainly due to restrictions in diode properties, including the incapability for a diode to exhibit a low threshold voltage and a high breakdown voltage simultaneously, resulting in a degradation in power efficiency in RF-DC conversion [4]. The effect of breakdown voltage, identified as early breakdown voltage [9] can be, in fact, one of the significant issues affecting the rectifier's efficiency. Therefore, some approaches have been proposed to obtain a rectifier capable of handling a wide dynamic range of input power levels while exhibiting high Power Conversion Efficiency (PCE). In [1, 2], the concept of a resistance compression network (RCN) has been introduced to improve the overall rectifier efficiency by attaining a small discrepancy of the input impedance while varying the output load and input power level, thus reducing the sensitivity of the input impedance rectifier versus the input power level and output load. However, the targeted input power range is still narrow. In [3, 10], a rectifier with a tunable configuration has been proposed to work over a wide dynamic input power range but at the cost of a complex and bulky design where different rectifiers operating at different power level capabilities are combined in a single-pole four-throw RF switch structure. In [9, 11], a topology utilizing a series diode associated with a pseudomorphic High-Electron-Mobility Transistor (pHEMT) transistor has been suggested to extend the breakdown voltage. However, such a configuration needs to be improved to cover wider input power levels. Also, maximum power point tracking (MPPT) approaches have been utilized to expand and enhance the overall conversion efficiency of the rectifier [12, 13]. In [14], a nonlinear model has been proposed to rectify and recycle the harmonics with the aim of increasing the RF-DC power conversion efficiency. Moreover, an automatic load control has been proposed in [15] to improve the PCE by changing the load according to the input power variation. Furthermore, a rectifier array has been presented to extend the range of the rectification process as in [16]. Also, to extend the power range of the rectifier, an asymmetric power divider has been proposed in [17]. So, to efficiently address the issues of low efficiency and narrow input power dynamic range in conventional rectifiers, an adaptive/reconfigurable rectifier technique has been proposed to simultaneously exhibit a low threshold voltage and a high breakdown voltage [4, 18]. Then, to extend its voltage breakdown, an active load modulation block [19] was added to the adaptive rectifier [20]. From that, after introducing the proof of concept of the adaptive rectifier with active load modulation in the above previous works [4, 20], and to further demonstrate its capabilities and enhance its performance, this paper first introduces a power link budget of the proposed adaptive rectifier as well as an estimation of a compromise between distance and efficiency.