INFINITESIMAL DIPOLE ANTENNAS & WEARABLE ANTENNAS

Group 11

Presented By:

• SINDHUJA M• SINDHUJA S• SRIKKANTH SRIDHAR• SUJITHA T• MANIVANNAN R• GANGADHARAN

Classification of Wire Antenna Elements

Electrical Size

• Electrical Size of an Antenna - the physical dimensions of the antenna defined relative to wavelength.

• Electrically small antenna - the dimensions of the antenna are small relative to wavelength.

• Electrically large antenna - the dimensions of the antenna are large relative to wavelength.

Infinitesimal Dipole Antenna

• The simplest type of wire antennas is infinitesimal dipole antenna.

• The antenna is assumed to be inifnitesimal if its length L is much less than the wavelength: L << λ.

• Typically: L < λ/50 and very thin: r << λ .

Geometry

Radiation Patterns

• Both, electric and magnetic fields depend on the angle and have a maximum when = 900 (the direction perpendicular to the dipole axis) and a minimum when = 00.

Field Regions of the Infinitesimal Dipole

• We may separate the fields of the infinitesimal dipole into the three

• standard regions:• Reactive near field kr << 1• Radiating near field kr > 1• Far field kr >> 1(r>> λ/2π)

Near-Field Region (Reactive near field)

• Components are in phase-Quadrature (i.e They are orthogonal to each other.)

• It is mathematically equivalent to that of a D.C Current Segment.

Near field equations

Intermediate Field(Radiating Near Field)

• The radial Component of the electric field diminishes.

• As r gets very large the radial component is reduced to zero.

• E and H are now in phase which yields a Poynting vector for these two components which is purely real (radiation).

Far-Field

• The Field consists only of two components which are orthogonal to each other. Thus this is now a TEM plane wave.

• Wave Impedance is equal to the impedance of the medium.

• The Field equations are obtained by substituting kr>>1.

Far-Field Equations

Radiation Pattern in 3D

Applications

• Used to Model other antennas.• Used to model Capacitor-Plate Antennas

Capacitor Plate Antennas

Wearable Antennas

• A wearable antenna is meant to be a part of the clothing used for communication purposes, which includes tracking and navigation, mobile computing and public safety.

• Thus Wearable antennas have to be flexible and also at the same time their performance must not deteriorate while bending.

Difficulty in Wearable Antennas

• In the case of on-body environment, it is diffcult to keep the wearable antenna un-bent all the time and it becomes bent quite often due to body movements.

• The bending may modify the performance characteristics of the antenna as its resonant length gets altered.

• For the convenience of the user, wearable antennas need to be hidden and of low profile. This requires a possible integration of these antenna elements within everyday clothing.

• Microstrip patch is a representative candidate for any wearable application, as it can be made suitable for integration into clothing.

Fabric Substrate

Design of Textile Antennas

• A thin, conducting rectangular copper patch on an insulating fabric substrate backed by a copper ground plane.

Textile Rectangular Patch Antenna

Design Considerations:

• Ground Plane must be sufficiently large so as to minimize the radiation which enters the body from the patch antenna.

Radiation Patterns

• A large ground plane (120mm x 120mm) must be used in order to minimize the strength of the back lobe.

• Still the effects of radiation on body is not completely removed. A small amount of radiation may still pass through.

Design Parameters

Design Parameters

• Material: Polyester• Length : 47.9mm• Width: 55.43• Dimensions of Ground Plane: 120mmx120mm• Ground Plane: Copper• Patch material: Copper• Loss Tangent:0.01

• Substrate Thickness: 2.85 mm• Dielectric Constant : 1.44• Design Frequency : 2.45 GHz

Advantages & Applications

• Flexible & Unobtrusive.• Can be Extended for Bluetooth Systems.• Constant Communication possible

• Can Revolutionize communication and mobile phones.

• Enhances GPS Tracking for Military Personnel.• When Interfaced with Medical sensors, it

provides a continuous monitoring of health on the go.

• Safety and Navigation.