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    All-Textile On-Body Antenna for Military Applications
    (Ieee-Inst Electrical Electronics Engineers Inc, 2022) Celenk, Esra; Tokan, Nurhan Turker
    An all-textile cavity-backed substrate integrated waveguide (SIW) antenna is proposed for military applications. The antenna matches standard military badge size. The aircraft-shape badge antenna that operates in X-band is designed for air force. SIW cavity and meandered slots that form the body and wing of the figure provide resonance at 8 GHz with 26% bandwidth. Symmetrical boresight patterns with very low sidelobes are observed. The measured gain and efficiency of the structure are 5.2 dBi and 79.2% at 8 GHz, respectively. This efficiency value is the highest among other SIW cavity textile-antennas. The antenna is investigated on conformal surfaces, as well. Bending of the antenna to follow body movements does not deteriorate performance of the textile antenna sensor. The peak specific absorption rate value over 10 g of tissue was 0.53 and 0.69 W/kg for 30 dBm input power for female and male breasts, which makes it suitable as an on-body antenna. The badge antenna is fabricated with standard textile fabrication techniques and its simulation performance is confirmed successfully by measurements. Usage of standard off-the-shelf parts for the assembly and fabrication with standard textile fabrication techniques enables simple and cost-effective mass production of the proposed badge antenna.
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    All-Textile On-Body Metasurface Antenna
    (Electromagnetics Acad, 2022) Celenk, Esra; Tokan, Nurhan T.
    In this work, a novel all-textile washable metasurface antenna is designed for WBAN/WLAN and mid-band 5G applications. Metasurface antenna is obtained by implanting SRR (Split Ring Resonator) metamaterials that show left-hand characteristics to the patch plane. The metamaterial arrays consisting of 4 x 1 and 4 x 2 SRRs are placed to lateral sides of a circular patch. The performance of the antenna is verified by a full-wave electromagnetic analysis tool. The results show that metamaterial arrays significantly increase gain and efficiency values of the circular patch antenna. Metasurface antenna consisting of 4 x 2 array of metamaterials increases the efficiency from 74% to 94.5% and the antenna gain from 6.81 dBi to 9.43 dBi. Performance of the antenna is observed on conformal surfaces, as well. An analysis is carried out to calculate the peak specific absorption rate on an arm phantom. Patterns of vertically bended antenna in circle divide =0 degrees and 90 degrees planes and low SAR values up to 30dBm input power proved suitability of the metasurface antennas for on-body applications. The antennas are fabricated by using standard textile manufacturing techniques. It was confirmed by the measurement results that the metasurface formed by the linear SRR arrays increases the antenna gain. With its low cost, fabrication with standard off-the-shelf parts, high gain, and efficiency features, the proposed antenna can be used in wireless body area networks and 5G applications.
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    Frequency Scanning Conformal Sensor Based on SIW Metamaterial Antenna
    (Ieee-Inst Electrical Electronics Engineers Inc, 2021) Celenk, Esra; Tokan, Nurhan Turken
    A conformal transverse slotted substrate integrated waveguide (SIW) metamaterial leaky-wave antenna sensor with uniform slots is investigated and analyzed for mmWave sensing applications. Firstly, its planar version is introduced. Then, its performance is compared with the curved SIW antenna. The metamaterial characteristics of the antennas are investigated. The transverse slots on the array forms a composite right/left-handed (CRLH) metamaterial structure that controls the radiation direction as the function of frequency. It behaves like a left handed metamaterial and radiates backward in the lower frequencies of the band (28-45GHz), whereas it behaves like a right handed metamaterial that scans forward direction at the higher frequencies (45-62GHz). Approximately 80 degrees beam scanning is obtained in curved version with acceptable side lobe levels, whereas 110 degrees beam steering is achieved with the planar version. Theoretical analysis and the simulation results are confirmed successfully by the experimental results in the 28-40 GHz band. Besides, a practical example of conformal SIW metamaterial antenna on military helmet made of a ballistic material is illustrated. The calculated spatial peak power density values of the proposed curved SIW metamaterial antenna on the outer surface of a head phantom are demonstrated.