Περίληψη
Η τεχνολογία των φορετών κεραιών και ηλεκτρονικών αναπτύσσεται ραγδαία τις τελευταίες δεκαετίες και οδηγεί σε ένα μέλλον όπου τα “έξυπνα“ (smart) υφάσματα θα ενσωματωθούν στα ρούχα μας. Ωστόσο, η έρευνα, σε αυτή την τεχνολογία, περιλαμβάνει άλυτα και διάφορα ζητήματα και προκλήσεις. Η παρούσα διδακτορική διατριβή ασχολείται με προκλήσεις όσον αφορά το χαρακτηρισμό και τις μετρήσεις φορετών κεραιών, την τροφοδοσία υφασμάτινων κεραιών και τη διασύνδεση υφασμάτινων γραμμών μεταφοράς. Όσον αφορά το χαρακτηρισμό και τις μετρήσεις φορετών κεραιών, παρουσίαζονται, η σχεδίαση ενός καινοτόμου υγρού ομοιώματος (phantom) ανθρωπίνου κορμού και μια νέα μεθοδολογία για την αξιολόγηση της απόδοσης φορετών κεραιών, χρησιμοποιώντας την τεχνική μέτρησης του κυλινδρικού κοντινού πεδίου (cylindrical near field). Όσο για την τροφοδοσία των υφασμάτινων κεραιών και τη διασύνδεση υφασμάτινων γραμμών μεταφοράς, παρουσιάζονται δύο καινοτόμες μέθοδοι.
Περίληψη σε άλλη γλώσσα
Wearable antennas and electronics technology rapidly grows the last decades and leads to a future where smart textiles will be integrated into our garments. However the wearable technology research includes unsolved or of different approach challenges. This thesis deals with challenges regarding wearable antenna characterization and measurements, textile antennas feeding and textile transmission lines interconnecting. Regarding the wearable antenna characterization and measurements, a novel design of a liquid torso phantom and a new methodology for evaluating wearable antenna performance by using the cylindrical near field measurement technique are proposed. As for the textile antennas and transmission lines feeding and interconnecting, two novel methods are proposed. This thesis presents the design, realization and evaluation of a low cost and lightweight hollow oval cross-section (HOCS) torso phantom appropriate for wearable antenna performance assessment in the frequency range of 2- ...
Wearable antennas and electronics technology rapidly grows the last decades and leads to a future where smart textiles will be integrated into our garments. However the wearable technology research includes unsolved or of different approach challenges. This thesis deals with challenges regarding wearable antenna characterization and measurements, textile antennas feeding and textile transmission lines interconnecting. Regarding the wearable antenna characterization and measurements, a novel design of a liquid torso phantom and a new methodology for evaluating wearable antenna performance by using the cylindrical near field measurement technique are proposed. As for the textile antennas and transmission lines feeding and interconnecting, two novel methods are proposed. This thesis presents the design, realization and evaluation of a low cost and lightweight hollow oval cross-section (HOCS) torso phantom appropriate for wearable antenna performance assessment in the frequency range of 2-6GHz. The phantom consists of an empty inner space (hollow) surrounded by a shell with double plastic walls between which there is at issue simulating liquid. The phantom’s plastic shell is made of a low loss cast acrylic and the liquid is a commercially available one. The HOCS phantom is compared with a corresponding full liquid torso phantom and a numerical heterogeneous anthropomorphic voxel phantom via simulations. Measurements with the realized HOCS phantom are compared with human subjects and a realistic homogeneous anthropomorphic solid phantom. The proposed HOCS phantom is evaluated as a good candidate for wearable antenna performance assessment including reflection coefficient, near field (E-field), on-body communication link budget and far field measurements. Additionally a new methodology, which uses the cylindrical near field (CNF) measurement technique, to evaluate wearable antennas performance parameters, is presented. For this methodology the proposed HOCS phantom and three patch antennas operating at 2; 2.5 and5GHz, appropriate for Off-body communication link, are used. The main advantage of this methodology is that less measurement space is required compared to a conventional far field test site and the use of a heavy duty roll axis, so as to rotate the phantom for 3D pattern coverage is excluded compared to a conventional spherical near field test site. An evaluation technique which is targeted for the CNF test site appropriate for wearable antenna measurements mounted on HOCS torso phantom is proposed and described. The goal of the evaluation technique is to find the optimum CNF measurement volume which would result into transformed far field parameters which will be closest to the simulation far field results. The evaluation technique is assessed by comparing the far field performance parameters (gain, directivity and efficiency),derived from the CNF measurements, with simulations and with direct far field measurements carried out inside a characterized full wave chamber. Validation of the evaluation technique is carried out by applying the derived optimum CNF volumes on the HOCS phantom, for the three antennas, and then measuring and comparing the results with simulations. Finally, the new methodology is described by measuring the patch antennas performance on HOCS phantom by using the CNF technique. The patch antennas are mounted in different locations on the HOCS phantom. The new methodology can be summarized as follows: The near field (E-field) for each antenna in each location is recorded; from the E-field results, assumptions for the maximum direction of radiation are derived and verified from the transformed far field radiation patterns. The far field parameters (gain, directivity) are produced from the near field results, verifying the assumptions made from the near field results about the directivity. Regarding the textile transmission lines (TL), two new methods for interconnecting textile TL are presented in terms of design and fabrication: (a) “slotted overlap” (SO) and (b)“complementary overlap” (CO). The proposed TL interconnection models follow the basic structure of a stripline. A straight stripline, without interconnections, is used as a reference and it is compared with the proposed interconnection methods. The investigated methods exclude the use of rigid coaxial connectors for the interconnection. The most efficient method, CO, is fabricated with purely textile materials (all-textile) so as to meet the “wearable criteria”. For this method the use of Velcro is investigated to provide practical and flexible interconnection characteristics. Additionally, the two interconnecting methods (SO and CO) described above are also investigated for feeding textile patch antennas with striplines. This result into corresponding structures which include a feeding stripline and a textile patch antenna (operating at 2.5GHz). The proposed antennas are probe and microstrip fed ones corresponding to the SO and CO interconnecting methods respectively. For the evaluation of the CO interconnecting/feeding method, an antenna prototype is designed and fabricated as an all-textile, practical and flexible structure. From measurements and simulations the CO antenna feeding method is proved as an efficient one. Finally, the CO concept implementation is enhanced by the demonstration of a real life wearable scenario.
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