Ultra wide band antenna
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Ultra wide band antenna

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Ultra wide band antenna Presentation Transcript

  • 1. Ultra Wide-Band AntennaPrepared By:Krunal Siddhapathak(10BEC097)
  • 2. Outline
  • 3. Introduction Ultra-wideband (UWB) communication systemshave the promise of very high bandwidth reduced fading from multipath low power requirements. The main concept behind UWB radio systems isthat they transmit pulses of very short duration, asopposed to traditional communication schemes,which send sinusoidal waves The role that UWB antennas play in all of this isthat they have to be able to transmit these pulsesas accurately and efficiently as possible.
  • 4. Introduction (Contd.)
  • 5. UWB Frequency-Domain SignalLink Characterization The transmit antenna is excited with a continuous wave signalwith the frequency f . The relevant parameters for the frequency-domain linkdescription are: AMPLITUDE OF TRANSMITTED SIGNALUTX(F) IN [V]; amplitude of receive signal Urx(f) in [V]; radiated field strength at a position r ETX. transfer function of the transmit antenna. transfer function of the received antenna. characteristic transmit antenna impedance. characteristic receive antenna impedance. Antenna gain. Distance between Tx-Rx antenna.
  • 6.  the transmit antenna is excited with a impulse. The elements of the UWB time domain linkcharacterization are: AMPLITUDE OF TRANSMIT SIGNAL UTX(F) IN [V]; amplitude of receive signal Urx(f) in [V]; radiated field strength at a position r ETX. transfer function of the transmit antenna. transfer function of the received antenna. characteristic transmit antenna impedance. Distance between Tx-Rx antenna.UWB Time-Domain Signal LinkCharacterization
  • 7. Antenna CharacterizationParameter1) Peak Value of theEnvelope: The peak valueof the analytic envelopeh+(t) is a measure for themaximal value of thestrongest peak of theantenna’s time-domaintransient response envelope.2) Gain in FrequencyDomain: The gain infrequency domain is definedlike in narrow-band systems.
  • 8. Antenna CharacterizationParameter (Contd.)3)Envelope Width: The envelope width describes thebroadening of the radiated impulse and is defined as the widthof the magnitude of the analytic envelope at half maximum(FWHM).4) Ringing: The ringing Tt of a UWB antenna is undesired andusually caused by resonances due to energy storage or multiplereflections in the antenna. It results in oscillations of theradiated pulse after the main peak.5) Transient Gain: The transient gain gT is an integral qualitymeasure that characterizes the ability of an antenna to radiatethe power of a given waveform uTx6) Group Delay: The group delay of an antenna characterizesthe frequency dependence of the time delay.
  • 9. UWB ANTENNA PRINCIPLESThe ultra-wide bandwidth radiation is basedon a few principles:1. traveling-wave structures2. frequency-independent antennas3. self-complementary antennas4. multiple resonance antenna5. electrically small antennas.
  • 10. Traveling-Wave Antennas Traveling-wave antennasoffer for the guided wavea smooth, almost notrecognizable transitionwith the fieldsaccelerated to free-spacepropagation speed co Typical antennas aretapered wave guideantenna e.g horn antenna,Vivaldi antennas Aperture coupled Vivaldiantenna. (Left) Top view;(right)bottom view with feedline.
  • 11. Frequency-Independent Antennas If wavelength and size ofantenna is scaled by samefactor than radiation patternwill remain same this typeof antenna are calledfrequency independent.
  • 12. Self-Complementary Antennas It is an arbitrary shapedantenna Antenna constitute half ofan infinitely extendedplanar-sheet conductor suchthat the shape of itscomplementary structure isexactly identical with thatof the originalstructure with two terminalsfor the simplest case. The self-complementaryantenna has constant inputimpedance independent ofthe source frequency andthe shape of the structure.Truncated fractal antenna toshow the principle of self-complementary antennas.
  • 13. Self-Complementary Antennas(Contd.) Type of self complementary antenna depends on numbers ofterminal, number of reference plane and others They also have constant-impedance property independent ofthe source frequency and the shape of the structure forrespective classes of structures with various grades ofcomplexity. This general principle is called “Principle of Self-Complementarity”. (This is also called “Mushiake Principle”on the Internet.) This principle is applicable also to thestructures other than antennas
  • 14. Multiple Resonance antenna Multiple resonance antennasare combinations ofmultiple, narrow-band,radiating elements. Each element for example, adipole covers a limitedbandwidth, e.g., 20% of thetotal UWB bandwidth.Typical candidates are theLog-Per and fractalantennas.Log-Per antenna with a coaxialconnector feeding the inner triplateline.
  • 15. Electrically Small Antennas
  • 16. Conclusion Ultra-wide-band as an emerging technology requires for theantenna characterization a thorough knowledge of thebehaviour in time domain, in frequency domain, and, incertain cases, in the spatial domain. It has been shown that forultra-wide-band, certain antenna classes can be definedaccording to their radiating characteristics.