# Eco-Friendly Metadome-Antenna Innovations for Wearable Millimeter Wave Radar Sensing
## 5 Conclusions  
A compact, light, flexible and low-cost meta-randomized microstrip grid array antenna (MTR-GAA) was designed and fabricated on eco-friendly Al-cladded PP, providing suitable matching and radiation properties for wearable ETA radar application at 24 GHz.  
The use of the metadome to protect the antenna allows for obtaining a device (MTR-GAA ensemble) that is even more compact than the monolithic thin radome and with better performance, preserving the good conditions of impedance matching bandwidth and radiation properties of the starting GAA.  
The MTR-GAA based on Al-cladded PP can be fabricated with common printed circuit board techniques (milling machining); therefore, the cost is not increased compared to using conventional materials that are neither environmentally friendly nor flexible.  
Moreover, PP is hundreds of times cheaper than commercial dielectrics with relative dielectric permittivity values in the same range.  
In addition, the assembly of the MTR-GAA ensemble by means of screws facilitates both the reuse and the disassembly and subsequent recycling of the devices.  
Furthermore, the recyclability of both PP and Al materials contributes to the circular economy and reduces the environmental footprint.  
Conceptualization, M.E.d.C.G.; methodology, formal analysis and investigation, M.E.d.C.G.; validation, M.E.d.C.G. and A.F.B.; data curation, M.E.d.C.G.; writing--original draft preparation and visualization M.E.d.C.G.; writing--review and editing, M.E.d.C.G. and A.F.B.; supervision. M.E.d.C.G. and F.L.-H.A.; project administration: M.E.d.C.G.; funding acquisition, M.E.d.C.G. and F.L.-H.A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Ministerio de Ciencia, e Innovacion of Spanish Government and Spanish Research Agency under project META-IMAGER PID2021-122697 OB-I00 and project TED2021-131975A-I00 and by the Government of Asturias-Sekuens/FEDER under grant IDE-2024-000693.  
Not applicable.  
The original data presented in the study are openly available in Mendeley Data, at doi: 10.17632/3 yc8x8z982.1 (accessed on 6 February 2025).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Ref.** & **G (dBi)** & **n (\%)** & **SLL (dB)** & **HPBW (\({}^{\circ}\))** & **SLL (dB)** & **HPBW (\({}^{\circ}\))** \\  & & & \(\varphi=0^{\circ}\) & \(\varphi=0^{\circ}\) & \(\varphi=90^{\circ}\) & \(\varphi=90^{\circ}\) \\ \hline
[16] & 20.6 & - & \(-15\) & \(16\) & \(-25\) & \(16\) \\
[31] & 7.4 & 35 & - & \(54\) & \(-25\) & \(48\) \\
[32] & 16.8 & 91 & \(-18\) & \(9.2\) & \(-25\) & \(64\) \\
[34] & 20.8 & 98 & \(-17\) & \(15\) & \(-20\) & \(16\) \\
[37] & 17 & - & \(-20\) & \(12\) & \(-20\) & \(50\) \\
[39] & 17 & - & \(-18\) & \(8.2\) & \(-18\) & \(80\) \\
[40] & 21.7 & 60 & \(-21\) & \(3.6\) & \(-21\) & \(46\) \\
[41] & 22.7 & 96 & \(-21\) & \(13\) & \(-23\) & \(10\) \\
[42] & 18.7 & - & \(-19\) & \(8\) & - & - \\
[49] & 8 & - & \(-10\) & \(60\) & \(-20\) & \(30\) \\
[50] & 20.6 & 88 & \(-15\) & \(15\) & \(-15\) & \(15\) \\
[51] & 9.8 & 87 & - & - & - & - \\
[52] & 25.9 & - & \(-20\) & \(15\) & \(-24.5\) & \(13.3\) \\ This work & 14 & 93 & \(-30\) & \(30\) & \(-15\) & \(40\) \\ This + MTR & 13.4 & 88 & \(-20\) & \(30\) & \(-15\) & \(40\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Radiation properties.  
Conflicts of Interest: The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.