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

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

3. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Outline Introduction Multi Element Antenna (MEA) Systems Evaluation Compact Printed MEA Systems Design Diversity and MIMO Systems Performance Conclusions

4. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Modern Antenna Systems Demands 1.Mitigation of fading in wireless communications Diversity techniques at the receiver 2.Requirements for higher data rate communications Multiple Input Multiple Output (MIMO) wireless systems

5. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Printed versus Non Printed Antennas 1.Zero-cost 2.Ease of fabrication 3.Ease of integration in small terminals 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

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

7. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS MEA Systems Evaluation Criteria for achieving Diversity/MIMO performance Diversity performance metricMIMO performance metric Mean Effective Gain (MEG) Envelope Correlation Coefficient (ρ e ) Effective Diversity Gain (EDG) MIMO capacity (C)

8. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Criteria in Non Uniform Environment Mean Effective Gain (MEG) : Envelope correlation coefficient (ρ e ) : G (Ω) : active gain pattern E(Ω) : active electric field pattern P(Ω) : angular density function XPR : cross polarization power ratio Environment Characteristics

9. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Criteria in Uniform Environment Mean Effective Gain (MEG) : Envelope correlation coefficient (ρ e ) : Uniform Environment e rad : radiation efficiency

10. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Effective Diversity Gain Calculation + Effective Diversity Gain (EDG) CDF of SNR of the combined signal (CDF : Cumulative Distribution Function) Mean Effective Gain (MEG) : Envelope correlation coefficient (ρ e ) : P div : the received power level of the combined signal P ideal : the received power level of a dual-polarized isotropic radiator with unit radiation efficiency operating in the same environment P div and P ideal are read at the same probability level in a CDF versus SNR plot

11. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS MIMO Capacity Calculation The Capacity (C) of a N x N MIMO system when the channel state information is not known at the transmitter: The Transfer matrix T elements are evaluated using a generic MIMO channel model: Complex channel gain Number of multipath components Direction of ArrivalDirection of Departure P T : transmitted power σ 2 : noise power I N : NxN Identity matrix

12. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS 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. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Investigated MEA Systems Design Compact due to the use of :  device’s ground plane  fractal concepts (Minkowski monopole)  short circuit (Inverted F Antenna (IFA)) The layouts of the investigated compact printed Multi Element Antenna (MEA) systems

14. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS S ii parameters of MEA Systems (a)(b) (c) (d) (e) (a), (b), (c) measured (d), (e) simulated (IE3D) Antennas’ placement with respect to the ground plane The dimensions of the antenna elements In all cases the antennas are well tuned at 5.2 GHz ISM band (5.15 – 5.35 GHz) due to Γ i : reflection coefficient at i th antenna port

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

16. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Radiation Efficiencies of MEA Systems Perpendicular orientation causes comparatively high efficiencies Average e rad value drops as the number of branches increase Since |S ii | < -14dB for all cases the drop is solely attributed to the power coupled into the feed network (|S ij | 2 )

17. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS MEG, ρ e and EDG Results Propagation in a Uniform Environment Strong mutual coupling leads to saturation behavior Similarity of patterns due to symmetry

18. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS EDG Results in Non Uniform Environments Saturation behavior The uniform environment approximates the indoor scenarios and the elliptical distributions quite well Simpler equations for ρ e and MEG calculation can be utilized simplifying considerably the performance evaluation Interesting Remark

19. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS MIMO System Modeling Tx – Rx separation distance is 10m (d x,d y,d z ) = (20m,30m,3.5m)

20. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Propagation Scenario Description Single bounce scattering mechanisms uniformly distributed with the constraint to reside in the far field region of the Tx and Rx antenna arrays The θθ, θφ, φθ and φφ scattering 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. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS MIMO Capacity Results Propagation in the Indoor Environment The same transmitted power is used for all MIMO systems for a fair comparison The effects of both the correlation properties and the power transmission gain on channel capacity are taken into account Saturation behavior

22. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS 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. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Conclusions Antennas’ orientation and placement has an impact on the overall system’s performance 1. Vertical orientation of the closely spaced elements has proven to increase the elements’ efficiency by decreasing the corresponding mutual coupling 2. By appropriately placing the elements at the edge of the ground plane, pattern diversity was achieved.

24. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS 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 performance evaluation procedure

25. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Conclusions For both Diversity/MIMO systems an asymptotic behavior of performance was observer as the number of antenna elements increases 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 due to

26. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS 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. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Thank You!!!

28. UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Criteria in Uniform Environment Mean Effective Gain (MEG) : Envelope correlation coefficient (ρ e ) : Uniform Environment