# Wireless Power Transfer via Subterahertz-Wave
## 1 Introduction
Figure 2: Earlier reports of studies assessing rectenna DC output power for frequency [2; 3; 4; 5; 6; 7; 8; 9; 10; 13; 14; 15; 16; 17; 18; 22; 23; 24]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reference No.** & **Frequency** & **DC Output** & **RF–DC Conversion** & & \\
**No.** & **[GHz]** & **[mW]** & **Efficiency [\%]** & **Antenna** & **Diode** \\ \hline
[2] & 2.33 & 2012 & 64 & MSL patch & GaAs FET \\
[3] & 2.45/5.8 & 75.6/40.6 & 84.4/82.7 & CPS dipole & GaAs SBD \\
[5] & 5.8 & 506.7 & 80.3 & Rectifier only & GaAs FET \\
[6] & 9.98 & 74.5 & 75 & MSL patch & SBD \\
[7] & 24 & NA & 65.5 & NA & GaAs SBD \\
[17] & 24 & 100.6 & 47.9 & MSL patch & MMIC \\
[23] & 28 & 140.8 & 47.7 & MSL patch & GaAs SBD \\
[4] & 10/35 & \(\times\)81/46.8 & 60/39 & MSL dipole & GaAs SBD \\
[8] & 35 & NA & 72 & MSL patch & GaAs SBD \\
[9] & 35.7 & 4.69 & 67 & MSL patch & GaAs SBD \\
[10] & 60 & 1.22 & 32.8 & Grid antenna & CMOS \\
[13] & 71 & 0.25 & 8 & Monopole & CMOS \\
[14] & 94 & 0.65 & 32.3 & Bow-tie slot & GaAs SBD \\
[15] & 35/94 & \(\times\)1.6/0.9 & 53/37 & Taper slot & CMOS \\
[16] & 94 & 0.1 & 10 & Dipole & CMOS \\
[22] & 94 & 15 & 20.5 & MSL patch & Mott diode \\
[18] & 94 & 39 & 38 & Rectifier only & GaAs SBD \\
[24] & 303 & 17.1 & 2.17 & MSL patch & GaAs SBD \\ \hline \hline \end{tabular} \(\times\)Value is not specified.  
\end{table} 
Table 1: Characteristics of rectenna in earlier studies (MSL: Microstrip line, CPS: Coplanar slot line, SBD: Schottky barrier diode). Figure 3: Earlier reports of studies examining rectenna power density for frequency [2; 4; 5; 14; 15; 16; 17; 18; 22; 23; 24]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Reference No.** & [17] & [15] & [8] & [4] & [9] & **This Work** [23] \\ \hline
**Frequency** & 24 & 35 & 35 & 35 & 35.7 & **28** \\
**[GHz]** & & & & & & \\ \hline
**Transmission Line** & MSL & Slot \& & & MSL & MSL & **MSL** \\ \hline
**Technology** & MMIC & CMOS & Dielectric & & & & **Diclad880** \\  & & 0.13 μm & Board & & & **(Rogers)** \\ \hline
**Architecture** & Class F load & \begin{tabular}{c} Taper slot \\ antenna+ \\ Transition + \\ BPF + \\ Rectifier \\ \end{tabular} & \begin{tabular}{c} MSL patch \\ antenna + \\ Rectifier \\ \end{tabular} & \begin{tabular}{c} MSL patch 4 \\ Rectifier \\ \end{tabular} & \
\begin{tabular}{c} MSL patch + \\ \(\times\) 4 array + \\ LPF + \\ Rectifier \\ \end{tabular} &
\begin{tabular}{c} MSL patch + \\ \(\mathbf{Class F}\) load \\ \(\mathbf{+}\) Rectifier \\ \end{tabular} \\ \hline
**Diode** & NA & \begin{tabular}{c} CMOS \\ Shottky \\ diode \\ \end{tabular} & GaAs SBD & \begin{tabular}{c} GaAs SBD \\ (DMK6606 Alpha) \\ \end{tabular} & \
\begin{tabular}{c} GaAs SBD \\ (MA4E1317 \\ MACOM) \\ \end{tabular} &
\begin{tabular}{c} GaAs SBD \\ (MA4E1317 \\ MACOM) \\ \end{tabular} \\ \hline
**Antenna Gain [dBi]** & - & 7.4 & NA & NA & 19 & **9.0** \\ \hline
**Oscillator** & NA & \begin{tabular}{c} Network \\ Analyzer \\ \end{tabular} & \
\begin{tabular}{c} Gunn \\ Oscillator \& \\ TWTA \\ \end{tabular} & Gunn Oscillator &
\begin{tabular}{c} Signal \\ Generator \\ \end{tabular} & **Gyrotron** \\ \hline
**Oscillator** & NA & \(\sim\)20 dBm & \(\sim\)500 & 0.2 & \(\sim\)20 dBm & **52,900** \\
**Power [W]** & & & & & & \\ \hline
**Rectenna** & & & & & & \\
**DC Output** & 100.6 & 1.6 & NA & 46.8 & 4.69 & **1050** \\
**Power [mW]** & & & & & & \\ \hline
**RF-DC** & & & & & & \\
**Conversion Efficiency** & 47.9 & 53 & 72 & 39 & 67 & **47.7** \\
**[\%]** & & & & & & \\ \hline
**Load** & & & & & & \\
**Resistance [\(\mathbf{\Omega}\)]** & 120 & 100 & NA & 100 & 1000 & **130** \\ \hline
**Rectenna** & & & & & & \\
**size [mm\({}^{2}\)]** & & & & & & \\ \hline
**Rectenna** & & & & & & \\
**Power** & & & & & & \\
**density** & & & & & & \\
**[KW/m\({}^{2}\)]** & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of this work to earlier studies in K - Ka band (CPW: Coplanar waveguide, GCPW: Grounded coplanar waveguide, BPF: Band-pass filter, LPF: Low-pass filter).