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Novel Antennas for flexible and Wearable Wireless Systems

Novel Antennas for flexible and Wearable Wireless Systems. Dr. Haider Khaleel Department of Engineering Science Sonoma State University 11 September 2012. Outline. Review Introduction Research Motivation Aims and Objectives Development of Flexible and Compact Antennas Applications

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Novel Antennas for flexible and Wearable Wireless Systems

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  1. Novel Antennas for flexible and Wearable Wireless Systems Dr. HaiderKhaleel Department of Engineering Science Sonoma State University 11 September 2012

  2. Outline • Review • Introduction • Research Motivation • Aims and Objectives • Development of Flexible and Compact Antennas • Applications • Conclusions and Future Work Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  3. What is an antenna? • The American Heritage Dictionary: A metallic apparatus for sending and receiving electromagnetic waves. • Webster’s Dictionary: A usually metallic device (as a rod or wire) for radiating or receiving radio waves. • Balanis; Antenna Theory: An antenna is a transitional structure between free-space and a guiding structure. HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  4. Why it is important? • Cellular communications, wireless networking between computers. • Cell Phones, PDAs, GPS, Peripherals, remote controls, wireless routers, wireless network cards, gaming consoles, RFID, etc… HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  5. Radiation Mechanism R HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  6. Antenna Types HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  7. Antenna Parameters • Resonant Frequency • Bandwidth • Impedance • Polarization • Radiation Pattern • Gain • Efficiency HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  8. Antenna Resonance An RF antenna is a form of tuned circuit consisting of inductance and capacitance, and as a result it has a resonant frequency. This is the frequency where the capacitive and inductive reactances cancel each other out. At this point the RF antenna appears purely resistive, the resistance being a combination of the loss resistance and the radiation resistance. The capacitance and inductance of an RF antenna are determined by its physical properties and the environment where it is located. The major feature of the RF antenna design is its dimensions.  Always remember! C=λF HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  9. Antenna Reflection Coefficient S11 HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  10. Antenna Bandwidth • Most RF antenna designs are operated around the resonant point. • Only a limited bandwidth over which an RF antenna design can operate efficiently. Outside this, the levels of reactance rise to levels that may be too high for satisfactory operation.  • The antenna bandwidth is particularly important where radio transmitters are concerned as damage may occur to the transmitter. HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  11. Polarization • Polarization is the orientation of electric field component of an EM wave relative to the Earth’s surface.  • Polarization is important to get the maximum performance from the antennas • There are different types of polarization (depending on existence and changes of different electric fields) • Linear (only Ex or Ey) • Horizontal • Vertical • Dual polarized • Circular (Ex and Ey) • Similar to satellite communications • TX and RX antennas must agree on direction of rotation • Elliptical Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  12. Antenna Radiation Power Let us consider a transmitting antenna (transmitter) is located at the origin of a spherical coordinate system. In the far-field, the radiated waves resemble plane waves propagating in the radiation direction and time-harmonic fields can be related by the equations: Electric and Magnetic Fields: The time-averaged power density vector of the wave is found by the Poynting Theorem Power Density: The total power radiated by the antenna is found by integrating over a closed spherical surface, Radiated Power: HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  13. Antenna Efficiency Power is fed to an antenna through a T-Line and the antenna appears as a complex impedance where the antenna resistance consists of radiation resistance and a dissipative resistance. For the antenna is driven by phasor current The power radiated by the antenna is The power dissipated by ohmic losses is An antenna efficiency e can be defined as the ratio of the radiated power to the total power fed to the antenna. HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  14. Directivity • The power density the antenna radiates in the direction of its strongest emission, versus the power density radiated by an ideal isotropic radiator. • The directivity of an actual antenna can vary from 1.76 dBi for a short dipole to as much as 50 dBi for a large reflector antenna. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  15. Antenna Gain The power gain, G, of an antenna is very much like its directive gain, but also takes into account efficiency The maximum power gain The maximum power gain is often expressed in dB. HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  16. Example Suppose an antenna has D = 4, Rrad = 40  and Rdiss = 10 . Find antenna efficiency and maximum power gain. Antenna efficiency Maximum power gain Maximum power gain in dB Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  17. Outline • Review • Introduction • Research Motivation • Aims and Objectives • Development of Flexible and Compact Antennas • Applications • Conclusions and Future Work Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  18. Flexible and Wearable Electronics • A research priority of many national research agencies. • The revenue is estimated to be 30 billion USD in 2017 and +300 billion USD in 2028. HaiderKhaleel, Department of Engineering Science, Sonoma State University 2012

  19. Flexible and Wearable Electronics Ref. [2] Ref. [1] Ref. [3] Ref. [4] Ref. [5] Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  20. Flexible and Wearable Wireless Systems • Require the integration of antennas to provide wireless connectivity. Design Requirements: • Light weight • Low profile • Conformable • Robust • Good performance Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  21. Objectives • Development of flexible, compact, robust, low profile, and efficient antennas. • Performance characterization of antennas when subjected to bending and rolling. • Utilizing the proposed antennas in practical applications. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  22. Previous Work Ref. [16] Ref. [17] Ref. [14] Ref. [15] • Paper based • Delicate • Permanent • folds • High loss • Disposable Textile Antennas • Bulky • High profile • Absorbability • Discontinuity • Complicated Process Fluidic Antennas • Limited to basic • geometries. • Discontinuity • Fragile • Complicated Process • Liquid Crystal Polymer (LCP) • Semi flexible • Low tensile strength • Large designs • 0.25 mm in thickness Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  23. Developed Designs Kapton Polyimide substrate • Low thickness (50.8 µm) • High tensile strength (165 MPA) • High flexibility (50000 psi) • Very low loss (0.002) • High thermal stability • *Published in IEEE Journal of Display Technology and IEEE Antennas and Wireless Propagation. 2012, HaiderKhaleel, Hussain Al-Rizzo, and Daniel Rucker. • Coplanar waveguide feeds • Compact Designs • Inkjet printing • Multiple bands Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  24. Fabrication Methods Screen Printing • Non uniform • Limited resolution • Waste material • Chemical Etching • Lengthy process • By-products • Multistep • Low production • Inkjet Printing • High resolution • Additive • Clean • Roll to roll Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  25. Single Band Printed Monopole 38 mm x 25 mm Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  26. Flexibility Tests Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  27. Radiation Patterns . Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  28. Comparison Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  29. Ultra Wide Band Antenna 47mm x 33mm • UWB has the advantages of: • High data rate • Low power • Simple hardware config. • UWB applications: • Wireless PC peripherals • Multimedia connectivity • Network access for mobile computing devices • Wireless Body Area Networks (WBAN) Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  30. Tapered Vs. Straight Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  31. Radiation Patterns Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  32. Outline • Review • Introduction • Research Motivation • Aims and Objectives • Development of Flexible and Compact Antennas • Applications • Conclusions and Future Work Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  33. MIMO • “MIMO is the use of multiple antennas at both the transmitter and receiver to improve communication performance”. • Limited wireless throughput • Power limitations • Fading, interference, noise Ref. [19] Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  34. Mutual Coupling Reduction between Flexible Printed Monopoles Using Bridged SRRs • Reduction of mutual coupling is essential to the performance of Multiple Input Multiple Output (MIMO) systems since it affects: • The current distribution and phase. • Input impedance • Radiation pattern in each antenna element. Reduces the capacity of MIMO systems. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  35. Previous Work • CSRR • For microstrips EBG & soft surfaces Involve vias MNG structures • Proposed previously for high profile monopoles Defected ground plane • For microstrips. . Ref. [20] Ref. [21] Ref. [22] Ref. [23] Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  36. Proposed Design λ =122mm 75mm x 37mm This section is published in the journal of Applied Computational Electromagnetics, and submitted to IEEE transaction on Antennas and Prop. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  37. Surface Current and Far-field Radiation Patterns . Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  38. S-Parameters and Envelope Correlation . Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  39. SAR Reduction in Telemedicine Systems • “Telemedicineis the use of medical information exchanged from one site to another via electronic communications to improve patients' health status”. American Telemedicine Association. • Telemedicine applications: • Seniors monitoring • Post surgery patients recovery tracking • Monitoring the body performance of astronauts and athletes. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  40. Remote Health Monitoring Scheme Ref. [24] Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  41. Antennas in Telemedicine Antennas must be: • Planar • Compact • Conformal • Robust and reliable Two choices: Microstrip and Printed dipole/monopole antennas • Light weight • Reduced SAR • Resilient to impedance mismatch Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  42. Microstrip vs. Printed Monopole • Microstrips are inherently narrow band antennas. • Printed monopoles are wide band antennas. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  43. Objective • Design a reliable wideband antenna with a hemi spherical radiation pattern. • Isolate the patient’s body from undesired electromagnetic radiation while keeping antenna’s required characteristics. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  44. Previous Work • Adding cavity or shielding plane • Using absorbers • SNG metamaterial • Textile EBG • Drawbacks: • Increase in height • Complicated manufacturing • Decreased efficiency • Large designs Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  45. AMC based Design 64mm 64mm Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  46. Reflection Coefficient Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  47. Radiation patterns and S-parameters Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  48. SAR Analysis • The Specific Absorption Rate (SAR) is a standard used to evaluate power deposition in human tissues. • SAR= • SAR value must not exceed the exposure guidelines specified by the Federal Communication Commission (FCC). • The maximum allowed SAR in USA and Canada is 1.6 W/kg averaged over 1g of tissue. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  49. SAR Analysis Antenna is simulated an a numerical human model (Hugo) with and without AMC. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

  50. SAR Analysis • For a 125 mW input power, the proposed design shows a SAR value of 0.638 W/Kg while the same antenna without AMC experienced a 1.88 W/Kg which is above the specified limit allowed by the FCC. Haider Khaleel, Department of Engineering Science, Sonoma State University 2012

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