without changing the radio hardware itself. not only the wireless network but also the different wireless devices
Broad topic, we on antennaEmphesize that one antenna can work in only one frequecy band
Gain any dep. On app (dire. Long range then more req.), know less inerference req. so low gainUltarwide band?Short linearLong dist circu..less lossesPolarization=Linear S11 set 10 abovevswe gr8er 2 if this (energy rerflected) totaallly ref. avoid not possible
Parametric:- kowing which parameteres sensitive: that should be accurateCstr used for all
Coaxi TEM-> Quasi TEM in micstrip (wave from one medium to another)Radlosss, dielsctric lossTEM quasi TEM?Impp change…
Zo 50 so 50 req. (power loss 50 at 73 ohm and so on)Tapering ??Capa diff tapering if so smoothHigh cap??
Gain depends on this..
Single mode to mode overlapping.
UWB Antenna for Cogntive Radio Application
Studies on Microstrip PatchAntennas for Cognitive Radio (Under the Guidance of Prof. M. V. Kartikeyan) Bhanwar Singh Prateek Batla Pratik Kumar
Overview• Motivation and Scope• Problem Statement• Literature Survey• Work Done – Simulation – Hardware Realization• Results and Discussions• Future Work• Publications
Cognitive Radio• First proposed by Joseph Mitola III in 1998• A radio that can change its transmitter parameters based on interaction with the environment in which it works.• Currently under development
Need for CR• Available wireless bandwidth is limited and most of it is already allocated to different wireless services.• But some of the allocated spectrum remains idle most of the time.• Cognitive Radio makes use of spectrum when it is idle.
Requisite for Antennas• Monitoring of spectrum – To find out which part of spectrum is idle. Requires UWB antenna which can sense a broader bandwidth.• Reconfigurablity – Change parameters to work in idle part of spectrum. Requires a narrowband reconfigurable antenna.
Problem Statement• To design, fabricate and test a UWB antenna for CR with following specifications –• BW = 3.1 to 10.6 GHz• S11 < -10 dB• Gain < 5 dB• Pattern = Approximately Omni directional
Feeding – Why CPW, not MS ?• Mode purity• Truly planar structure, can easily be mounted.• Less radiation and dielectric loss.• Higher impedances can be realized, 30 -140 Ω.• Same impedance can be realized using different feed gap and feed width
Impedance Matching• Input impedance should be close to 50 Ω.• Tapering – Changing feed width and gap.• Abrupt changes introduce parasitic reactive elements which can be very high at higher frequencies, hence avoided.
Parametric Analysis• Investigate antenna by varying one parameter and keep all others constant.• Results to notice are |S11| and input line impedance.• Important parameters are dimensions of ellipse, gap between ellipse and ground, feed length and tapering parameters.
Gain Frequency Simulated Gain Experimental Gain 3.46GHz 2.655dB 2.342dB 5.5GHz 4.076dB 3.985dB 11GHz 4.885dB 4.462dB• Low frequencies -> Long Wavelength -> Standing Waves -> Oscillating mode -> Less Gain• High frequencies -> Travelling mode -> More Gain
Limitations• Radiation pattern bandwidth of antenna is very short.• Contact losses are very high at high frequencies as port is simply soldered to the antenna feeding system.
Publication Under Review• National Conference on “RECENT TRENDS IN MICROWAVE TECHNIQUES AND APPLICATIONS”, organized by “University of Rajasthan, Jaipur”• A Planar Elliptical Monopole Antenna for UWB Applications ( Ref. No. MW1258)• Antenna System for Cognitive Radio Application (Ref No. MW1257)
Important References• Y. Tawk, and C. G. Christodoulou, Member, IEEE, A New Reconfigurable Antenna Design for Cognitive Radio• Elham Ebrahimi, James R. Kelly, Peter S. Hall, Integrated Wide-Narrowband Antenna for Multi-Standard Radio, IEEE TRANSACTIONS ON ANTEN-NAS AND PROPAGATION, VOL. 59, NO. 7, JULY 2011• J. Liang, C Chiau, X. Chen and C.G. Parini, Study of a Printed Circular Disc Monopole Antenna for UWB Systems", IEEE Transactions on Antennas and Propagation, vol. 53, no. 11, November 2005, pp.3500-3504.• C.A. Balanis, Antenna Theory and Analysis, 2nd ed., Wiley, New York, 1997 D. M. Pozar, Microwave and RF Design of Wireless System, Wiley, New York, 2001.• CST’s user manual “www.cst.com”