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Compact Printed Antennas for Small Diversity and MIMO Terminals. Professor V. Makios Laboratory of Electromagnetics Department of Electrical and Computer Engineering University of Patras Patras, Greece. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS.
Compact PrintedAntennasforSmallDiversity and MIMO TerminalsProfessor V. MakiosLaboratory of ElectromagneticsDepartment of Electrical and Computer EngineeringUniversity of PatrasPatras, GreeceUNIVERSITY OF PATRASELECTRICAL & COMPUTER ENG. DEPT.LABORATORY OF ELECTROMAGNETICSLaboratory of ElectromagneticsAntenna groupProfessor C. Soras (Director)Dr. M. KaraboikisDr. G. TsachtsirisV. PapamichaelUNIVERSITY OF PATRASELECTRICAL & COMPUTER ENG. DEPT.LABORATORY OF ELECTROMAGNETICSOutline
  • Introduction
  • Multi Element Antenna (MEA) Systems Evaluation
  • Compact Printed MEA Systems Design
  • Diversity and MIMO Systems Performance
  • Conclusions
  • Modern Antenna Systems Demands
  • Mitigation of fading in wireless communications
  • Diversity techniques at the receiver
  • Requirements for higher data rate communications
  • Multiple Input Multiple Output (MIMO) wireless systemsPrinted versus Non Printed AntennasSo far in the major part of literature for Diversity and MIMO applications
  • Non-printed antennas (Planar Inverted F Antennas or dipole arrays)
  • Up to 3-element printed antennas have been proposed
  • Advantages of Printed Antennas
  • Zero-cost
  • Ease of fabrication
  • Ease of integration in small terminals
  • Trade-off in Diversity/MIMO PerformanceRestricted space of small terminal deviceIncreasing the number of integrated antennasDiversity and MIMO performance is enhancedStrong mutual coupling among antenna elementsQueryWhat is the maximum number of printed elements in a compact Diversity/MIMO system terminal for maximum performance ?MEA Systems EvaluationCriteria for achieving Diversity/MIMO performance
  • Mean Effective Gain (MEG)
  • Envelope Correlation Coefficient (ρe)
  • Diversity performance metricMIMO performance metric
  • Effective Diversity Gain (EDG)
  • MIMO capacity (C)
  • Criteria in Non Uniform EnvironmentMean Effective Gain(MEG) :Envelope correlation coefficient (ρe) :G(Ω):active gain patternE(Ω):active electric field patternP(Ω): angular density functionXPR: cross polarization power ratioEnvironmentCharacteristicsCriteria in Uniform EnvironmentUniform EnvironmentMean Effective Gain(MEG) :erad: radiation efficiencyEnvelope correlation coefficient (ρe) :Effective Diversity Gain CalculationMean Effective Gain (MEG) :CDF of SNR of the combined signal(CDF : Cumulative Distribution Function)+Envelope correlation coefficient (ρe) :Effective Diversity Gain (EDG)Pdiv: the received power level of the combined signalPideal: the received power level of a dual-polarized isotropic radiator with unit radiation efficiency operating in the same environmentPdivand Pideal are read at the same probability level in a CDF versus SNR plotMIMO Capacity CalculationThe Capacity (C) of a N x N MIMO system when the channel state information is not known at the transmitter:PT:transmitted powerσ2:noise powerIN: NxN Identity matrixThe Transfer matrix Telements are evaluated using a generic MIMO channel model:Direction of ArrivalDirection of DepartureNumber of multipath componentsComplex channel gainInvestigated MEA Systems DesignThe layouts of the investigatedcompact printed Multi Element Antenna (MEA) systems
  • Compact due to the use of :
  • device’s ground plane
  • fractal concepts
  • (Minkowski monopole)
  • short circuit
  • (Inverted F Antenna (IFA))
  • Investigated MEA Systems DesignThe layouts of the investigatedcompact printed Multi Element Antenna (MEA) systems
  • Compact due to the use of :
  • device’s ground plane
  • fractal concepts
  • (Minkowski monopole)
  • short circuit
  • (Inverted F Antenna (IFA))
  • Sii parameters of MEA Systems(a)(b)Γi : reflection coefficient at ith antenna portIn all cases the antennas are well tuned at 5.2 GHz ISM band (5.15 – 5.35 GHz)(c)(d)due to
  • Antennas’ placement with respect to the ground plane
  • The dimensions of the antenna elements
  • (e)(a), (b), (c) measured(d), (e) simulated (IE3D)Active Gain Patterns of MEA Systems(a)(b)In all cases the patterns exhibit complementary performance (pattern diversity)(d)(c)due toAntennas’ placement with respect to the ground plane which affects their radiation characteristics(e)All patterns aresimulated using IE3DRadiation Efficiencies of MEA SystemsAverage erad value drops as the number of branches increaseSince |Sii| < -14dB for all cases the drop is solely attributed to the power coupled into the feed network (|Sij|2)Perpendicular orientation causes comparatively high efficienciesMEG, ρe and EDG ResultsPropagation in a Uniform EnvironmentSimilarity of patterns due to symmetryStrong mutual coupling leads to saturation behaviorEDG Results in Non Uniform EnvironmentsInteresting RemarkThe uniform environment approximates the indoor scenarios and the elliptical distributions quite wellSimpler equations for ρe and MEG calculation can be utilized simplifying considerably the performance evaluationSaturation behaviorMIMO System ModelingTx – Rx separation distance is 10m(dx,dy,dz) = (20m,30m,3.5m)Propagation Scenario DescriptionSingle bounce scattering mechanisms uniformly distributed with the constraint to reside in the far fieldregion of the Tx and Rx antenna arraysThe θθ, θφ, φθ and φφscattering coefficients of the channel’s complex gain are complex Gaussian variables with zero mean and unit varianceT matrix is realized 6000 times assuming L=21 multipath componentsMIMO Capacity ResultsPropagation in the Indoor EnvironmentThe same transmitted power is used for all MIMO systems for a fair comparisonSaturation behaviorThe effects of both the correlation properties and the power transmission gain on channel capacity are taken into accountConclusionsAll systems satisfy the Diversity/MIMO criteriaThe high directivity elliptical distribution propagation scenario provides the maximum EDG (16.4 dB)The maximum 1 % outage capacity achieved with unknown channel state information at the transmitter is 20.4 bps/Hz for the five-element systemConclusionsAntennas’ orientation and placement has an impacton the overall system’s performance
  • Vertical orientation of the closely spaced elements has proven to increase the elements’ efficiency by decreasing the corresponding mutual coupling
  • By appropriately placing the elements at the edge of the ground plane, pattern diversity was achieved.
  • ConclusionsAccording to the results, the uniform power distribution model is a very good approximation for the indoor scenarios (Gaussian, Laplacian and Elliptical)Considerable simplifications of the diversity performanceevaluation procedureConclusionsFor both Diversity/MIMO systems an asymptotic behaviorof performance was observer as the numberof antenna elements increasesdue toMutual coupling among closely spaced elements which causes radiation efficiency reductionAn upper limit of five IFA/Minkowski elements in a PC card for the 5.2 GHz ISM band is posedFuture WorkThe use of compact decoupling networks in order to increase the upper limit of efficient printed antennas onto a small Diversity/MIMO terminal deviceThe performance of compact multi element antenna under various MIMO selection algorithms should be investigatedThank You!!!Criteria in Uniform EnvironmentUniform EnvironmentMean Effective Gain(MEG) :Envelope correlation coefficient (ρe) :
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