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. 2022 Feb 8;22(3):1276.
doi: 10.3390/s22031276.

Flexible and Transparent Circularly Polarized Patch Antenna for Reliable Unobtrusive Wearable Wireless Communications

Abu Sadat Md Sayem  1   2 , Roy B V B Simorangkir  3 , Karu P Esselle  1 , Ali Lalbakhsh  2 , Dinesh R Gawade  3 , Brendan O'Flynn  3 , John L Buckley  3
Affiliations

Flexible and Transparent Circularly Polarized Patch Antenna for Reliable Unobtrusive Wearable Wireless Communications

Abu Sadat Md Sayem et al. Sensors (Basel). .

Abstract

This paper presents a circularly polarized flexible and transparent circular patch antenna suitable for body-worn wireless-communications. Circular polarization is highly beneficial in wearable wireless communications, where antennas, as a key component of the RF front-end, operate in dynamic environments, such as the human body. The demonstrated antenna is realized with highly flexible, robust and transparent conductive-fabric-polymer composite. The performance of the explored flexible-transparent antenna is also compared with its non-transparent counterpart manufactured with non-transparent conductive fabric. This comparison further demonstrates the suitability of the proposed materials for the target unobtrusive wearable applications. Detailed numerical and experimental investigations are explored in this paper to verify the proposed design. Moreover, the compatibility of the antenna in wearable applications is evaluated by testing the performance on a forearm phantom and calculating the specific absorption rate (SAR).

Keywords: circular polarization; flexible; polymer; transparent; wearable.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Geometry of the proposed flexible and transparent CP antenna: (a) top view, (b) side view, (c) bottom view.
Figure 2
Figure 2
Surface current distribution of the antenna at 2.4 GHz at the time phases (a) 0°, (b) 90°, (c) 180° and (d) 270°.
Figure 3
Figure 3
|S11| vs. frequency when varying the radius of the slot of the ground plane.
Figure 4
Figure 4
Peak gain vs. frequency when varying the radius of the slot of the ground plane.
Figure 5
Figure 5
Radiation efficiency vs. frequency when varying the radius of the slot of the ground plane.
Figure 6
Figure 6
Radiation patterns (in dB) at the corresponding resonance frequencies when varying the radius of the slot of the ground plane.
Figure 7
Figure 7
The antenna topology under bending.
Figure 8
Figure 8
|S11| vs. frequency of the antenna for different bending radius.
Figure 9
Figure 9
Peak gain vs. frequency of the antenna for different bending radius.
Figure 10
Figure 10
The effect of the PDMS encapsulation on the |S11| of the antenna.
Figure 11
Figure 11
The effect of the PDMS encapsulation on the peak gain of the antenna.
Figure 12
Figure 12
Schematic representation of the antenna fabrication process.
Figure 13
Figure 13
Fabricated prototypes: (a) transparent and non-transparent antenna prototypes, (b) transparent antenna in bent state.
Figure 14
Figure 14
Antenna on top of the forearm phantom: (a) perspective view, (b) cross-sectional view.
Figure 15
Figure 15
Peak gain vs. frequency when varying the separation between the antenna and phantom.
Figure 16
Figure 16
Radiation efficiency vs. frequency when varying the separation between the antenna and phantom.
Figure 17
Figure 17
SAR at 2.4 GHz when varying the separation between the antenna and phantom.
Figure 18
Figure 18
SAR distributions in the forearm phantom at: (a) 2.4 GHz, (b) 2.45 GHz and (c) 2.6 GHz.
Figure 19
Figure 19
Antenna on top of the multilayer phantom: (a) cross-sectional view, (b) perspective view. (Rbn = 12.5 mm, Rms = 40 mm, Rft = 48.5 mm, Rsk = 50 mm).
Figure 20
Figure 20
SAR distributions in the multilayer phantom at: (a) 2.4 GHz, (b) 2.45 GHz and (c) 2.6 GHz.
Figure 21
Figure 21
Antenna |S11| measurement set-up: (a) antenna bending towards the x-axis direction, (b) antenna bending towards the y-axis direction, and (c) flat antenna.
Figure 22
Figure 22
Simulated and measured |S11| vs. frequency: (a) transparent antenna, (b) non-transparent antenna.
Figure 23
Figure 23
Antenna measurement set-up inside the AMS-8050 Antenna Measurement System.
Figure 24
Figure 24
Simulated and measured peak gain vs. frequency of the transparent and non-transparent antennas.
Figure 25
Figure 25
Simulated and measured total efficiency vs. frequency of the transparent and non-transparent antennas.
Figure 26
Figure 26
Simulated and measured axial ratio vs. frequency: (a) transparent antenna, (b) non-transparent antenna.
Figure 27
Figure 27
Simulated and measured far-field radiation patterns of the transparent antenna at 2.4 GHz: (a) unbent state, (b) bent state.
Figure 27
Figure 27
Simulated and measured far-field radiation patterns of the transparent antenna at 2.4 GHz: (a) unbent state, (b) bent state.
Figure 28
Figure 28
Simulated and measured far-field radiation patterns of the non-transparent antenna at 2.4 GHz: (a) unbent state, (b) bent state.
See this image and copyright information in PMC

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