Outline Introduction Paper: Paper: Antenna Designs Antenna - - PowerPoint PPT Presentation

Paper presentation – Ultra-Portable Devices

Paper: Paper:

Akram Alomainy,Yang Hao and David M Davenport ”Parametric St d f W bl A t ith V i Di t f th Study of Wearable Antennas with Varying Distances from the Body and Different On-Body Positions” IET Seminar on Antennas and Propagation for Body-Centric Wireless Communications, London, UK, pp. 84-89, 2007

Presented by:

Rohit Chandra

2010-01-26 1 Paper Presentation - Ultra Portable Devices

Outline

• Introduction
• Antenna Designs
• Antenna Performance Analysis: Free Space vs Wearable
• Antenna Coupling Around the body
• Results of Antenna coupling on body
• Summary

2010-01-26 2 Paper Presentation - Ultra Portable Devices

Introduction

• WBAN’s radio system components including Antenna:

Hidd C t L W i ht Hidden, Compact, Low Weight

• Smart Clothing/Textile : Integration of RF system into cloth
• 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 3 Paper Presentation - Ultra Portable Devices

Introduction...

• Paper analyses:
• Antenna performance when placed on body
• Effect of distance variation and positions
• On body propagation channel
• Various antenna analyzed

2010-01-26 4 Paper Presentation - Ultra Portable Devices

Antenna Types Antenna Types

• Planar Antennas
• Printed on FR4 substrate, εr = 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

• 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

Wearable Antennas

• 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

• Loss in backward radiation
• Increased directivity because of

curvature of human body

Varying Distance Results

• 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

• Antennas with ground plane least affected by varying distance
• 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

Antenna coupling around body

• Transmitter at left waist and receiver at right chest and right thigh.

g g g

• Path Loss dependent on on-body link and type of antenna.

Reflection from ground

• Ground Modeled as PEC plane near the feet of the human model
• 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

Measurements Results

• Parasitic L at 4mm from

body

On Body Communication Link Loss Loss

• Monopole Antenna
• Tx at left waist
• Rx on right chest
• 18 different body

postures changing 20 seconds

Summary

• Antenna performance is different at different body positions

b f i ti i l t i l ti d t f because of variation in electrical properties and curvature of body.

• Planar antenna with ground planes are more suitable.
• Transmission loss depends on antenna type and property of

surrounding lossy material surrounding lossy material.

2010-01-26 18 Paper Presentation - Ultra Portable Devices