Smart Wearable Lenses on Kevlar Vests

Smart Wearable Lenses on Kevlar Vests. Authors: Vitor Freitas, Amit Baghel and Pedro Pinho Affiliations: Universidade de Aveiro and Instituto de Telecomunicações, Aveiro, Portugal.

Introduction. 2. Wireless Power Transfer (WPT) is a well-established concept, but key challenges remain [1]; Antennas emit energy as EM waves; however, their typically omnidirectional radiation leads to low transmission efficiency; To transmit power from a military transmission base to a soldier on the battlefield, who is wearing electronic devices, the energy must be transmitted from a transmitter antenna to a receiver antenna; Nowadays, the challenge lies in making reception equipment more compact while increasing efficiency in environments where signal propagation is more difficult [2]; There is also a need for greater mobility and effectiveness against signal jammers [2]..

Paper novelty. 3. Consists of using textiles to design a Fresnel lens (FZL), which are cheap and simple to manufacture; They can be sewn into any piece of cloth. This gives it great potential for military applications; The possibility arises of using FZL to further increase the efficiency of this process and achieve higher efficiencies [3][6]..

Implementation. 4. FZL made of textile sewn into a backpack, between a TX antenna and a RX antenna, that could be embedded in the Kevlar vest. Two scenarios will be analyzed: System without the receiving lens; System with the receiving lens..

System. 5. TX: a high directivity horn antenna with 18 dBi [11]; RX: a FZL made of different textiles with different permittivities; Focus point is 10 mm, to simulate the thickness of a conventional Kevlar vest, used by military personnel and law enforcement tactical units [4]..

FZL. 6. Limited space in the backpack requires a small and compact lens; A multi-dielectric design was chosen because it is intended to be attached to a piece of clothing; Advantages: Lens has the same thickness throughout; Less affected by the shadow blocking effect, since it has a continuous surface without steps. This enables an F/D ratio smaller than 0.5 [7]; More versatile, allowing us to position the lens in a way that is convenient for the soldier..

FZL design. 7. F is the focal point, 10 mm; The design frequency is 5.8 GHz; A quarter-wave was used, P = 4 and N = 4; ϵ1 is 3.4, since it is the highest value found in the research while having the minimum loss tangent possible; Thickness of 52 mm, any lowest thickness result in a permittivity lower than 1..

Simulations. 8. 1.5 times more than without the FZL is achieved; Demonstrates the effectiveness of using a multi-dielectric FZL made of textiles; Manipulating the waves guarantees a much more efficient system..

Conclusions. 9. Usage of FZL on the smart textile integrated into a Kevlar vest; The WPT system was designed at 5.8 GHz; The receiver includes a FZL composed of textile layers with varying permittivity to focus the incoming beam; Simulations demonstrate that the textile-based FZL significantly increases gain, offering a low-cost solution for enhancing charging efficiency; Greater autonomy in the field can be achieved for military applications, as well as reduced weight and dependence on fixed energy sources, and increased operational safety..

Future work. 10. Adding an antenna to be used as a receiver would allow us to better test the system by studying the S11, S21 and S22; Important to carry out tests in a real environment with real fabrics and physical configurations to validate the result; Tests with jammers to see how well the proposal works even when a jammer is in place..

Acknowledgments. 11. The present study was developed in the scope of the Project “Agenda ILLIANCE” [C644919832-00000035 — Project nº46], financed by PRR – Plano de Recuperação e Resiliência under the Next Generation EU from the European Union. This work was supported by FCT - Fundação para a Ciência e Tecnologia, I.P. by project reference UIDB/50008/2020,and DOI identifier 10.54499/UIDB/50008/2020,https://doi.org/10.54499/UIDB/50008/2020..

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Thank you!. 13.