Wearable Antennas and Body Centric Communication by Shiban Kishen Koul & Richa Bharadwaj

Author:Shiban Kishen Koul & Richa Bharadwaj
Language: eng
Format: epub
ISBN: 9789811639739
Publisher: Springer Singapore

Compact and low cost tapered slot coplanar waveguide fed UWB antennas (TSA) (Fig. 6.3b, [36]) were used as transmitters placed on the body and as receivers in the base stations (BS). The TSA antenna has dimensions of 27 × 16 mm2 and offers a return loss below −10 dB with good radiation performance and relatively constant gain across the UWB band when off, or on a human body.

The antennas were mounted on plastic frames with 3 reflective markers on each (Fig. 6.3b) to provide benchmark 3D position information through a VICON motion capture system [3]. The 8 cameras motion capture system which gives high accuracy results (better than 1 cm) was used to compare with the UWB localization results and to obtain reference coordinates of the base stations (receiver antennas) [37].

Frequency domain measurements were performed in the 3–10 GHz band using a 4-port vector network analyzer (VNA R&S ZVA-50) to capture S21 (channel transfer function) parameters between each transmitter antenna location on the body and the BS (receiver) antenna. For each BS and mobile station (MS) antenna position, the channel impulse response (CIR) was obtained from the S21 collected from the VNA set to 6400 data samples, which is adequate to obtain the required channel information. For the case of limb movement tracking, measurements were taken for each of the wearable antenna location and the data is further combined to get the overall limb localization in three dimensions. The subject is made to hold to a particular position before proceeding to the next position with the VNA scanning time of around 800 ms to mimic the limb motion, hence obtaining a pseudo-dynamic motion for the limbs. For the case of the whole body, the antenna is positioned at different locations and readings are taken from the VNA.

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