UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS

1. Compact PrintedAntennasforSmallDiversity 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

2. Laboratory of Electromagnetics Antenna group Professor C. Soras (Director) Dr. M. Karaboikis Dr. G. Tsachtsiris V. Papamichael UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS

3. Outline • Introduction • Multi Element Antenna (MEA) Systems Evaluation • Compact Printed MEA Systems Design • Diversity and MIMO Systems Performance • Conclusions

4. 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 systems

5. Printed versus Non Printed Antennas So 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

6. Trade-off in Diversity/MIMO Performance Restricted space of small terminal device Increasing the number of integrated antennas Diversity and MIMO performance is enhanced Strong mutual coupling among antenna elements Query What is the maximum number of printed elements in a compact Diversity/MIMO system terminal for maximum performance ?

7. MEA Systems Evaluation Criteria for achieving Diversity/MIMO performance • Mean Effective Gain (MEG) • Envelope Correlation Coefficient (ρe) Diversity performance metric MIMO performance metric • Effective Diversity Gain (EDG) • MIMO capacity (C)

8. Criteria in Non Uniform Environment Mean Effective Gain(MEG) : Envelope correlation coefficient (ρe) : G(Ω):active gain pattern E(Ω):active electric field pattern P(Ω): angular density function XPR: cross polarization power ratio Environment Characteristics

9. Criteria in Uniform Environment Uniform Environment Mean Effective Gain(MEG) : erad: radiation efficiency Envelope correlation coefficient (ρe) :

10. Effective Diversity Gain Calculation Mean 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 signal Pideal: the received power level of a dual-polarized isotropic radiator with unit radiation efficiency operating in the same environment Pdivand Pideal are read at the same probability level in a CDF versus SNR plot

11. MIMO Capacity Calculation The Capacity (C) of a N x N MIMO system when the channel state information is not known at the transmitter: PT:transmitted power σ2:noise power IN: NxN Identity matrix The Transfer matrix Telements are evaluated using a generic MIMO channel model: Direction of Arrival Direction of Departure Number of multipath components Complex channel gain

12. Investigated MEA Systems Design The layouts of the investigated compact 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))

13. Investigated MEA Systems Design The layouts of the investigated compact 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))

14. Sii parameters of MEA Systems (a) (b) Γi : reflection coefficient at ith antenna port In 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)

15. Active Gain Patterns of MEA Systems (a) (b) In all cases the patterns exhibit complementary performance (pattern diversity) (d) (c) due to Antennas’ placement with respect to the ground plane which affects their radiation characteristics (e) All patterns are simulated using IE3D

16. Radiation Efficiencies of MEA Systems Average erad value drops as the number of branches increase Since |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 efficiencies

17. MEG, ρe and EDG Results Propagation in a Uniform Environment Similarity of patterns due to symmetry Strong mutual coupling leads to saturation behavior

18. EDG Results in Non Uniform Environments Interesting Remark The uniform environment approximates the indoor scenarios and the elliptical distributions quite well Simpler equations for ρe and MEG calculation can be utilized simplifying considerably the performance evaluation Saturation behavior

19. MIMO System Modeling Tx – Rx separation distance is 10m (dx,dy,dz) = (20m,30m,3.5m)

20. Propagation Scenario Description Single bounce scattering mechanisms uniformly distributed with the constraint to reside in the far fieldregion of the Tx and Rx antenna arrays The θθ, θφ, φθ and φφscattering coefficients of the channel’s complex gain are complex Gaussian variables with zero mean and unit variance T matrix is realized 6000 times assuming L=21 multipath components

21. MIMO Capacity Results Propagation in the Indoor Environment The same transmitted power is used for all MIMO systems for a fair comparison Saturation behavior The effects of both the correlation properties and the power transmission gain on channel capacity are taken into account

22. Conclusions All systems satisfy the Diversity/MIMO criteria The 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 system

23. Conclusions Antennas’ orientation and placement has an impact on 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.

24. Conclusions According 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 procedure

25. Conclusions For both Diversity/MIMO systems an asymptotic behavior of performance was observer as the number of antenna elements increases due to Mutual coupling among closely spaced elements which causes radiation efficiency reduction An upper limit of five IFA/Minkowski elements in a PC card for the 5.2 GHz ISM band is posed

26. Future Work The use of compact decoupling networks in order to increase the upper limit of efficient printed antennas onto a small Diversity/MIMO terminal device The performance of compact multi element antenna under various MIMO selection algorithms should be investigated

27. Thank You!!!

28. Criteria in Uniform Environment Uniform Environment Mean Effective Gain(MEG) : Envelope correlation coefficient (ρe) :