with IEEE802.11b and Bluetooth

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12
-
13 February 2002

8
th

Australian Symposium on Antennas

1

Investigations into fixed
-
pattern
and adaptive antennas for use
with IEEE802.11b and Bluetooth
standards


by



K.S. Bialkowski, A. Postula & M.E. Bialkowski


School of Information Technology &
Electrical Engineering


University of Queensland

12
-
13 February 2002

8
th

Australian Symposium on Antennas

2

Presentation Outline


Rationale


Problems with traditional antennas


Antenna diversity techniques to
overcome propagation problems



Non
-
adaptive and adaptive antenna
solutions


Examples of investigated antennas


PC setup for assessing antenna
performances in a Bluetooth
communication system


Conclusions


12
-
13 February 2002

8
th

Australian Symposium on Antennas

3

Rationale


There is a strong demand for reducing the size
of wireless communication devices to open
new application areas




To meet this demand, reduced
-
size antennas
are required



New antenna designs
have to mitigate
problems associated with multi
-
path
propagation



The viable option are antennas offering
diversity

12
-
13 February 2002

8
th

Australian Symposium on Antennas

4

Problems with Traditional
Antennas


Traditional antennas (such as monopoles) are of
fixed pattern and polarization.



The transmitted wave is affected by
multi
-
path
propagation
resulting in large changes in the
received signal strength



In mobile environment, receiving antennas are
often pattern/polarization mismatched to the
incident wave

12
-
13 February 2002

8
th

Australian Symposium on Antennas

5

Options for Solving
Propagation Problems


Increase Transmitted Power



Disadvantage


(i) more battery power required


(ii) more radiated power absorbed by an operator



Use Antenna Diversity



By matching the receiving antenna

pattern
,
polarization

or
field

(E or H) the receiving system gain can be improved
by several dB




Advantage:


The quality of communication link can be improved
without
the need to compensate by an active gain


The battery can operate over an extended time period


Health hazards due to radiation are reduced

12
-
13 February 2002

8
th

Australian Symposium on Antennas

6

Antenna Diversity Options




Pattern diversity
:

the antenna pattern is matched to the
direction from which the wave arrives



Polarization diversity
:

the antenna polarization is matched to
the polarization of the incident wave




Field diversity
:

antenna elements are selected to couple to
E

or
H

field, whichever is maximum at a given location



All the above schemes
do not require large real estate
and
can be realized using a single or few antenna
elements.

12
-
13 February 2002

8
th

Australian Symposium on Antennas

7

Antenna Diversity Example


The following figures show signals received by
horizontally

and
vertically

polarized antennas in a
typical indoor environment.


The signals are affected by multi
-
path propagation.


H
owever, nulls are at different positions.



By alternating between the two polarizations good
quality signal reception can be maintained.


12
-
13 February 2002

8
th

Australian Symposium on Antennas

8

Non
-
Adaptive and Adaptive
Antenna Solutions


Non
-
Adaptive solution


offered by fixed
-
pattern
antennas featuring high cross
-
polar component




Used in (some of) current designs (Eg PIFA)


co
-
polar and cross
-
polar components observed in far
-
field
radiation pattern.



Adaptive Diversity solution
-
offered by antennas with
pattern controlled by a switching system:



Polarization Diversity


Signal is received on one of two (or more) polarizations, eg
Horizontal + Vertical, LHC+RHC


Pattern Diversity


Signal is received only from a selected direction

12
-
13 February 2002

8
th

Australian Symposium on Antennas

9

Investigated Antennas


Ericsson PIFA


Smart Clothing IFA


F Shaped Monopole


CPW Feed Patch Antenna


Single Circular Slot Antenna (LP and CP
Polarized)


Dual Slot Ring Antenna



All of them have been designed for operation
at 2.4GHz using Agilent ADS Momentum.


12
-
13 February 2002

8
th

Australian Symposium on Antennas

10

Fully Developed Antennas


Printed IFA




Single Slot Ring



Single Slot Ring


Polarization Diversity



Dual Slot Ring


Pattern Diversity Antenna

12
-
13 February 2002

8
th

Australian Symposium on Antennas

11

Printed IFA Design with
the Use of Momentum

3D Radiation Plot and Current Distributions

12
-
13 February 2002

8
th

Australian Symposium on Antennas

12

Fully Developed


Printed IFA


Non
-
adaptive antenna with high degree of
cross polarization

The developed antenna

12
-
13 February 2002

8
th

Australian Symposium on Antennas

13

Single Slot Ring (CP Feed)
Design with the Use of
Momentum



3D Radiation and Current Plot shown

12
-
13 February 2002

8
th

Australian Symposium on Antennas

14

Fully Developed Single Slot
Ring (CP Feed) Antenna


Circular Polarization (non adaptive) Antenna

The developed antenna

12
-
13 February 2002

8
th

Australian Symposium on Antennas

15

Operation of Single Slot Ring
with Perturbation Segments
Antenna



Perturbation segments


Are ON: circular polarization is obtained


Are OFF: linear polarization is achieved

12
-
13 February 2002

8
th

Australian Symposium on Antennas

16

Design of Single Slot Ring
with Perturbation Segments


Current Plots


With and without perturbation segments

12
-
13 February 2002

8
th

Australian Symposium on Antennas

17

Fully Developed Single Slot
Ring with Perturbation
Segments



Able to achieve Linear or Circular Polarization
depending on the state of its switches


Photographs of the developed
antenna

12
-
13 February 2002

8
th

Australian Symposium on Antennas

18

Dual Slot Ring Antenna

OFF

OFF

ON

OFF

Generates 3 independent radiation patterns by
turning ON or OFF P
-
I
-
N diodes

12
-
13 February 2002

8
th

Australian Symposium on Antennas

19

Fully Developed Dual Slot
Ring Antenna


Pattern Diversity Antenna

The developed
antenna

12
-
13 February 2002

8
th

Australian Symposium on Antennas

20

Experimental Results for
Antennas


The inverted IFA, Single Slot Ring, Single Slot
Ring with Perturbation Segments and Dual Slot
Ring antennas have been tested in terms of their
Return Loss using HP8510 Vector Network
Analyser



In general, good agreement with the Momentum
simulated results has been obtained



12
-
13 February 2002

8
th

Australian Symposium on Antennas

21

Bluetooth Experimental
Setup


Includes two Bluetooth Modules connected to


two PCs running Linux 2.4.20 with BlueZ 2.3



Uses 'Ping' link application over Bluetooth's l2cap
layer with ACL (connectionless) packets



Using this system, performances of a
Bluetooth link (
with antennas described previously
)
can be assessed in real time


The performance can be measured and plotted
vs location/distance of the receiving module.


12
-
13 February 2002

8
th

Australian Symposium on Antennas

22

Bluetooth Experimental
Setup [Photo]

T module

R module

12
-
13 February 2002

8
th

Australian Symposium on Antennas

23

Bluetooth Experiment


Includes:



measuring

mean packet delay and counting error
-
free packets of information received during the
transmission between the two PCs.



Measuring
the received signal power using the
Bluetooth RSSI command.



Measuring
BER estimations using CSR’s Bluetooth
Firmware


12
-
13 February 2002

8
th

Australian Symposium on Antennas

24

Bluetooth Experiment
Results [Real
-
time]

RSSI

BER/

Quality

Packet

Delay

The position of dots is related
to the link quality

12
-
13 February 2002

8
th

Australian Symposium on Antennas

25

Bluetooth Experiment
Results [
Power/Delay vs Distance
]

Delay

Power

50

100

2.5m + Distance (cm)

12
-
13 February 2002

8
th

Australian Symposium on Antennas

26

Conclusions


Fixed and variable pattern planar antennas to
mitigate multipath problems have been designed
and developed using Agilent ADS Momentum.




The antennas parameters have been selected
for operation with Bluetooth (2.4GHz).




Developed antennas were experimentally tested
and showed good performance.


12
-
13 February 2002

8
th

Australian Symposium on Antennas

27

Conclusions (continued)



A PC
-
based system has been developed to
measure in real time the communication link
quality between Bluetooth modules.



The system serves as an experimental platform
for assessing antenna diversity schemes for
Bluetooth.