This paper presents a detailed analysis of the human body limb movement influence on the radiation pattern of a wearable antenna during different activities. The analysis is carried out at 3, 6, 9 GHz of the 3-10 GHz UWB range of frequencies. Simulations are carried out on a human body model in CST microwave studio with a compact wearable antenna to obtain the body-worn antenna radiation patterns for lower and higher frequencies. This study gives an insight into the variation of the radiation patterns of a compact UWB antenna depending upon the position of the wearable antenna on the body. Results conclude that the radiation pattern of the wearable antenna changes significantly in terms of shape, size, level of distortion and direction of maximum radiation with different limb movement activities and also depends upon the placement of the antenna on the limbs. The coverage area of the wearable antenna radiation pattern becomes highly directive and shrinks in coverage area for the shoulder/thigh node in comparison to the wrist/ankle wearable node by 10-15%. The bending of the limbs leads to deformation and reduction in area of the radiation pattern with values as high as 30-40% compared to free space scenario as the bending angle between the upper and lower arm/leg reduces. The analysis presented gives directional information regarding maximum radiation and the field strength of the radiation pattern for various activities performed. The present study reports results on the influence of the wearable antenna position, on detection and tracking performance of RF and microwave biomedical devices/sensors suitable for various healthcare applications such as tracking of human subject, patient monitoring, gait analysis, physical exercises, yoga, physiotherapy, and rehabilitation.
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