Title: Investigations%20into%20Reduced-Size%20Antennas%20for%20Mobile%20Computing
1Investigations into Reduced-Size Antennas for
Mobile Computing
- by
- Konstanty Bialkowski
- School of Information Technology Electrical
Engineering - University of Queensland
2Rationale
- There is a strong demand for reducing the size of
mobile computers 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
3Problems 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
4Options for Solving Propagation Problems
- Increase Transmitted Power
- Disadvantage - battery can ran out quickly
- 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
5Antenna 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.
6Antenna 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. However, nulls are at different
positions.
7Non-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, LHCRHC - Pattern Diversity
- Signal is received only from a selected direction
8Investigated Antennas
- Ericsson PIFA
- Smart Clothing IFA
- Smart Clothing IFA Dual-Band
- F Shaped Monopole
- CPW Feed Patch Antenna
- Single 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.
9Fully Developed Antennas
- Smart Clothing IFA
- Single Slot Ring
- Single Slot Ring
- Polarization Diversity
- Dual Slot Ring
- Pattern Diversity Antenna
10IFA (for Smart Clothing)
- Non-adaptive antenna with high degree of cross
polarization
Photographs of the developed antenna
11IFA (for Smart Clothing)
- 3D Radiation Plot and Current Distributions
12Single Slot Ring (CP Feed)
- Circular Polarization (non adaptive) Antenna
Photographs of the developed antenna
13Single Slot Ring (CP Feed)
- 3D Radiation and Current Plot shown
14Single Slot Ring with Perturbation Segments
- Able to achieve Linear or Circular Polarization
depending on the state of its switches
- Photographs of the developed antenna
15Single Slot Ring Antenna Operation
- Perturbation segments
- Are ON circular polarization is obtained
- Are OFF linear polarization is achieved
16Single Slot Ring Simulations
- Current Plots
- With and without perturbation segments
17Dual Slot Ring Antenna (1)
- Pattern Diversity Antenna
Generates 3 independent radiation patterns by
turning ON or OFF P-I-N diodes
18Dual Slot Ring Antenna (2)
- Pattern Diversity Antenna
- Photographs of the developed antenna
19Dual Slot Ring Antenna(Far field radiation Plots)
20Dual Slot Ring Antenna(Current Plots)
21Experimental 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
22Bluetooth Experimental Setup
- Includes two Bluetooth Modules connected to
- Two PCs running Linux 2.4.19 with BlueZ 2.2
- Uses 'Ping' link application over Bluetooth's
l2cap layer - Using this system, performances of various
antennas described previously can be assessed in
real time - This task is accomplished by measuring mean
packet delay and counting error-free packets of
information received during the transmission
between the two PCs. -
23Bluetooth Experiment Results
24Conclusions
- Fixed and variable pattern planar antennas to
mitigate multipath problems have been analysed
using Agilent ADS Momentum. - The antennas parameters have been selected for
operation with Bluetooth. -
- Developed antennas have been experimentally
tested.
25Conclusions (continued)
- A PC-based system has been developed to assess
in real time the communication link between
Bluetooth modules. - The system serves as an experimental platform for
assessing antenna diversity schemes for Bluetooth.