Andrey GleenerAndrey Gleener R&D Services Ltd.a8421@intergate.cahttp://mypage.uniserve.ca/~a8421/Andrey-Gleener/

IEEE Joint Communications Chapter - Vancouver

Ideas for Embedded Antenna Design

For Small-Size and Hand-Held Devices

Apple iPhone Antenna

Antenna close to on-board components

antenna developer has to extend design thought onto the whole mechanical structure surrounding the Antenna

The Usual Antenna Properties:

• Frequency• Bandwidth• Radiation pattern• Gain• Efficiency• Polarization

Technological Details:

• Materials• Feed• Mounting

Issues specific to Embedded Antenna:

• Interaction with Surrounding Circuitry• Effects of Antenna Housing• Interaction with Human Body

Types of structures used as embedded antennas

Dipole

Monopole

Helix

Loop

Slot

Inverted FPatch

Currents localized on Antenna Structure

Currents forced on Ground Plane

Include Ground Plane to get larger effectiveaperture

Avoid GroundPlane if it is excessively lossy

Simple Embedded Antenna

Nordic Semiconductor evaluation board

Pattern as function of total length

L

< 1/4 λ

E

L = 1/2λ~

L = 1λ~~

~3/8 λ

~1/4 λ

E

~1/4 λ E

Polarization is Important

PIFA

Planar Inverted F Antenna

PIFA from Monopole

Monopole

Inverted L

Inverted F

PIFA

PIFA from Slot Antenna

Slot

Half-Slot

PIFA

Advantages of PIFA

• can be matched directly to 50 Ohm

• high efficiency in compact form factor

• reduced coupling to surrounding environment

• low Specific Absorption Rate

• can be made resonant in desired multiple frequency bands!

Dual Band PIFA

Slot

Return Loss of Dual Band PIFA Antenna

5%6%

Return Loss of modern multi band cellular Antenna

19% 21%

Mobile Phone Antenna Patterns

Patterns are not omnidirectionalPatterns are not optimal horizontallyPolarization is not entirely vertical

Proximity of User’s Hand and Headfurther changes the pattern

Trends in Embedded Antenna development:

• Multi-Antenna systems

• Antennas with reconfigurable geometry

• Integration of multiple dissimilar Antennas in one enclosure

• Use of Metamaterials in Antenna design

Antenna and Circuit on the same board

Inside Linksys Wi-Fi Card. Two Inverted-F Antennas arranged in diversity scheme. PCB Material around the antennas removed.

Ericsson T 200 Antenna

Heat Staking the Antenna

Antenna Matched Antenna Not Matched

• Antenna needs to be mounted specifically and precisely

• Antenna assembly must be highly repeatable from one assembly to another

• Antenna can not be loose or change position inside the package

• Any materials touching Antenna absorb energy

• Always verify that your Antenna is still matched when in production.