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Uwb antenna by debashish(IIT DELHI)
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Uwb antenna by debashish(IIT DELHI)

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understanding of uwb technology and design of uwb antenna for underwater application

understanding of uwb technology and design of uwb antenna for underwater application

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  • 1. UNDERSTANDING OF UWB TECHNOLOGY AND UWB ANTENNA DESIGN FOR UNDERWATER COMMUNICATIONS Submitted by DEBASHISH PRADHAN ENTRY ID-2013EEE8271 COURSE-EEL 760 Department of Electrical Engineering IIT DELHI
  • 2. What is ultra wide band(UWB)?  Ultra wide band is the band which occupies greater than 500 MHz of band width or greater than 25% of the operating center frequency.  FCC allocated the 3.1-10.6 GHz spectrum for unlicensed use .
  • 3. WHY UWB?  UWB technology transmit and receive pulse based waveform compressed in time .  So in frequency domain band width of pulse is very high.  Because of compressed time pulse data rate is very high and as the power of pulse is spread over the large frequency band so noise interference is very less.
  • 4. UWB ADVANTAGES  High data rates  Multiple-access capabilities, due to wide band width of transmission  Propagation through solid material, due to presence of energy at different frequencies.  Carrier less signal propagation  Simplicity in implementation, low cost of devices.
  • 5. UWB application  High resolution radar-for example detection and movement of objects near vehicle are more accurate  Wireless personal area network(WPAN)-Anyone can use  Military communication- The probability to detect UWB pulses is very low.  Imaging system-like ocean imaging medical diagnostic  Emergency situation- As UWB spectrum can penetrate obstacles .this property can be used to detect and rescue survivors in disaster situation
  • 6. UWB ANTENNA REQUIREMENTS  Band width-3.1-10.6 GHz  Radiation Efficiency-High(>70%)  Phase-Nearly Linear(constant group velocity)  Radiation Pattern-Omnidirectional  Directivity-low  HPBW-wide(>60)  Return loss-less(<-10db)
  • 7. Achieving Broader Bandwidth  There are several known antenna topologies that are said to achieve broader characteristics ,such as horn antenna , Biconical antenna ,Helix antenna ,Bowtie antenna ,spiral antenna. biconical antenna bowtie antenna helix antenna
  • 8. Bow-tie antenna  If we consider the case of dipole antenna for 300 mHz frequence then length should be 0.5 m (to behave as a half wave dipole antenna)  If the frequency changes radiation pattern changes as the length is fixed.  So the problem is that the above Half-Wavelength antenna design depends solely on length.  What if instead, we could design an antenna that was completely specified by Angles instead of Lengths? Angles do not depend on distance - and hence don't depend on wavelength.  One of the popular UWB antenna is Bow-tie antenna.
  • 9. VSWR of bow tie antenna  For L=76.5mm  D=1300  http://www.antenna-theory.com/antennas/wideband/bowtie.php
  • 10. Signal propagation in water  Aquatic communication are limited by two factor  1)low speed of sound  2)time varying multi path propagation  So alternative approach is Electro-magnetic wave communication.  Electromagnetic wave in water is only 9 times slower than air.  As attenuation factor is directly proportional to square root of freq and conductivity.  Propagation of high frequency component are not possible in water .
  • 11. Study of permittivity of water
  • 12. Under water antenna analysis  If we put the bow-tie antenna inside water(without any change in structure)  upcommons.upc.edu/.../UWB%20antenna%20design%20for%20underw
  • 13. Folded Bow-tie antenna analysis  It is the combination of circular loop and bow-tie antenna.  The radiation pattern and return loss depends on radius, angle , width, thickness, feeding and internal isolation of antenna.
  • 14. Parametric study Angle and width upcommons.upc.edu/.../UWB%20antenna%20design%20for%20underw
  • 15. Parametric study Thickness and gap feeding upcommons.upc.edu/.../UWB%20antenna%20design%20for%20underw
  • 16. Parametric study radius Choosing best dimensions (width,thickness……) Bw=1800 mhz-135mhz=1665mhz As bw>500mhz so the designed antenna is a uwb antenna upcommons.upc.edu/.../UWB%20antenna%20design%20for%20underw
  • 17. Radiation pattern(without internal isolation) upcommons.upc.edu/.../UWB%20antenna%20design% 20for%20underw
  • 18. Final shape with internal isolation  An antenna need battery and circuit to work but cannot be touching water  Thus we have to isolate center of antenna with sphere.  The sphere can be air or air Teflon ball.
  • 19. Radiation pattern(with isolation) upcommons.upc.edu/.../UWB%20antenna%20design%20for %20underw
  • 20. Conclusion  When the antenna has internal isolation ,the pattern is more omnidirectional.  Under water UWB communication is possible but within short range because of conductivity of water.