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

by K.S. Bialkowski, A. Postula & M.E. Bialkowski School of Information Technology & Electrical Engineering University of Queensland. Investigations into fixed-pattern and adaptive antennas for use with IEEE802.11b and Bluetooth standards. Rationale Problems with traditional antennas

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

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  1. by K.S. Bialkowski, A. Postula & M.E. Bialkowski School of Information Technology & Electrical Engineering University of Queensland Investigations into fixed-pattern and adaptive antennas for use with IEEE802.11b and Bluetooth standards

  2. 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 Presentation Outline

  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

  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

  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 antennapattern, polarizationor 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

  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.

  7. By alternating between the two polarizations good quality signal reception can be maintained. 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. • However, nulls are at different positions.

  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

  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.

  10. Fully Developed Antennas • Printed IFA • Single Slot Ring • Single Slot Ring Polarization Diversity • Dual Slot Ring Pattern Diversity Antenna

  11. Printed IFA Design with the Use of Momentum 3D Radiation Plot and Current Distributions

  12. Fully Developed Printed IFA • Non-adaptive antenna with high degree of cross polarization The developed antenna

  13. Single Slot Ring (CP Feed) Design with the Use of Momentum • 3D Radiation and Current Plot shown

  14. Fully Developed Single Slot Ring (CP Feed) Antenna • Circular Polarization (non adaptive) Antenna The developed antenna

  15. Operation of Single Slot Ring with Perturbation Segments Antenna • Perturbation segments • Are ON: circular polarization is obtained • Are OFF: linear polarization is achieved

  16. Design of Single Slot Ring with Perturbation Segments • Current Plots • With and without perturbation segments

  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

  18. OFF ON OFF OFF Dual Slot Ring Antenna Generates 3 independent radiation patterns by turning ON or OFF P-I-N diodes

  19. Fully Developed Dual Slot Ring Antenna • Pattern Diversity Antenna The developed antenna

  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

  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.

  22. Bluetooth Experimental Setup [Photo] R module T module

  23. Bluetooth Experiment • Includes: • measuringmean 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

  24. Bluetooth Experiment Results [Real-time] RSSI Packet Delay The position of dots is related to the link quality BER/ Quality

  25. Bluetooth Experiment Results [Power/Delay vs Distance] Power Delay 2.5m + Distance (cm) 50 100

  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.

  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.

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