Paper presentation – Ultra-Portable Devices Outline • Introduction Paper: Paper: • Antenna Designs • Antenna Performance Analysis: Free Space vs Wearable Akram Alomainy,Yang Hao and David M Davenport ” Parametric St d Study of Wearable Antennas with Varying Distances from the f W bl A t ith V i Di t f th • Antenna Coupling Around the body Body and Different On-Body Positions ” • Results of Antenna coupling on body IET Seminar on Antennas and Propagation for Body-Centric Wireless Communications, London, • Summary UK, pp. 84-89, 2007 Presented by: Rohit Chandra 2010-01-26 Paper Presentation - Ultra Portable Devices 1 2010-01-26 Paper Presentation - Ultra Portable Devices 2 Introduction Introduction... • WBAN’s radio system components including Antenna: • Paper analyses: Hidden, Compact, Low Weight Hidd C t L W i ht - Antenna performance when placed on body - Effect of distance variation and positions • Smart Clothing/Textile : Integration of RF system into cloth - On body propagation channel - Various antenna analyzed • Compact and low profile antennas for easy integration • Body Worn Antennas problems : reduced efficiency, pattern distortion, antenna detuning � transmission error, loss of communication Link communication Link 2010-01-26 Paper Presentation - Ultra Portable Devices 3 2010-01-26 Paper Presentation - Ultra Portable Devices 4
Antenna Types Antenna Types • Planar Antennas • Printed on FR4 substrate, ε r = 4.6, σ = .002 S/m • Thickness = 1.6mm ( for Wiggle = 0.7mm) • Analysis : finite Integral Technique in 2.4 GHz ISM band Analysis: Free Space Analysis • Excellent performance by conventional Antennas • Size reduction reduces antenna bandwidth and efficiency due to Size reduction reduces antenna bandwidth and efficiency due to coupling between elements and vias.
Wearable Antenna Analysis Wearable Antennas • Frequencies : 2.4, 2.44,2.48 GHz • Distance : 1 4 8 mm • Distance : 1,4,8 mm • Electric Properties of human body at 2.4 GHz • Detuning from Free Space: change in effective length due to lossy body • Printed Monopole and Parasitic L less detuning due to ground plane • Narrow band of Parasitic L: distance variation is less Narrow band of Parasitic L: distance variation is less Radiation Pattern Varying Distance Results • Loss in backward radiation • Increased directivity because of curvature of human body • Difference in Left and right chest because of difference in human physiological and electrical properties of tissues • Farther antenna more gain: reduction in absorbed power
Results Antenna coupling around body • Transmitter at left waist and receiver at right chest and right thigh. g g g • Antennas with ground plane least affected by varying distance • Path Loss dependent on on-body link and type of antenna. • Inverted L, parasitic L and wiggle antenna: narrowband performance from return • Inverted L parasitic L and wiggle antenna: narrowband performance from return loss and transmission loss analysis. • Narrow band antennas: unreliable even if slight detuning • Narrow band antennas: unreliable even if slight detuning • Creeping wave: diffraction of space wave because of body curvature Reflection from ground Measurements Results • Ground Modeled as PEC plane near the feet of the human model • Parasitic L at 4mm from body • Ground affects the link closer to ground like left waist – left ankle Ground affects the link closer to ground like left waist left ankle • Introduction of nulls in radiation pattern and Transmission coefficient due to MPC
On Body Communication Link Summary Loss Loss • Antenna performance is different at different body positions because of variation in electrical properties and curvature of b f i ti i l t i l ti d t f • Monopole Antenna body. • Tx at left waist • Rx on right chest • Planar antenna with ground planes are more suitable. • 18 different body postures changing • Transmission loss depends on antenna type and property of 20 seconds surrounding lossy material surrounding lossy material. 2010-01-26 Paper Presentation - Ultra Portable Devices 18
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