UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS A Hybrid Electromagnetic-Discrete Multipath Model for Diversity Performance Evaluation of Multi Element Antenna Systems V. Papamichael, C. Soras and 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 Outline Introduction Electromagnetic Discrete Multipath Model Diversity Performance Evaluation Antenna Systems Description Propagation Scenario and Input Parameters Simulation Results (MEG, ρ e, MEAG, DG, EDG) Conclusions

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Introduction Mitigation of fading in wireless communications Diversity techniques at the receiver Measurements Antenna s time and cost consuming not practical from the antenna designer point of view non – physical physical Performance evaluation of Diversity Systems Modeling Channe l analytically full wave

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS The two capabilities of a Diversity System :  the mitigation of multipath fading and  the capture of average power are separately calculated Diversity Systems Performance Evaluation Prior works  via measurements or  using simplified analytical models based on measurements This work Evaluates diversity performance through a new hybrid Electromagnetic Discrete Multipath (EMDM) model using:  physical modeling for the wireless channel and  full wave analysis for the antennas Distinct advantage of EMDM model

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Wireless Link in Free Space V R : Rx open-circuit voltage μ 0 : free space permeability ω : angular frequency h T\R : vector effective lengths Ω T0 : Direction of Departure (θ T0,φ T0 ) Ω R0 : Direction of Arrival (θ R0,φ R0 ) I T : input current at the Tx antenna k : wavenumber A : Tx antenna position vector B : Rx antenna position vector R : Tx-Rx separation distance

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Wireless Link in Multipath Environments D sp : specular depolarization operator r : total multipath length (r 1 + r 2 ) g 0 (r ) : spreading factor (1/4πr ) M : scattering mechanism position vector

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Electromagnetic-Discrete Multipath Model Voltage Transfer Function Circuit description of the Tx and n th Rx antennas of a SIMO System

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Vector Effective Length Calculation G(θ,φ) : active power gain pattern P(θ,φ) : active phase pattern R A : real part of the antenna input impedance U(θ,φ) : radiation intensity P in : input power at antenna (IE3D parameter) G IE3D (θ,φ) : active gain pattern from IE3D P tot : total generator power (IE3D parameter)

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Reference Antenna Characteristics Reference antenna selection is crucial for diversity performance evaluation Special ability : captures the maximum power without providing fading mitigation isotropic θ and φ gain patterns and π/4 linear polarization

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Criteria for Achieving Diversity Gain Mean Effective Gain (MEG) : Envelope correlation coefficient (ρ e ) : P n : received power at n th Rx antenna terminals

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Diversity Performance Metrics: 1. MEAG samples P div P ref P rec P rec : received power at Rx antenna terminals Z R : load impedance at Rx antenna terminals Received power by the reference antenna Received power by the diversity antenna system Mean Effective Array Gain

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Diversity Performance Metrics: 2. DG P div /E{P div } P ref /E{P ref } P rec Normalized received power by the reference antenna Normalized received power by the diversity antenna system Diversity Gain samples 1

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Diversity Performance Metrics: 3. EDG P div /E{P ref } P ref /E{P ref } P rec Effective Diversity Gain samples 1

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Investigated MEA Systems The layouts of the investigated compact 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))

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Investigated MEA Systems The layouts of the investigated compact 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))

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

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS EMDM Model’s Input Parameters ParameterPhysical meaning (units)Value hThT Transmitting antenna’s vector effective length (m) Computed using a MoM EM field solver hRhR Receiving antenna’s vector effective length (m) Z TA/RA Impedance of the Tx/Rx antennas (Ω) Z T/R Characteristic impedance of Tx/Rx feeding networks (Ω)50 d x xd y xd z Dimensions of the indoor environment (m 3 )30x20x3 APosition vector of Tx antenna phase center (m)(10,10,1.5) BPosition vector of Rx array phase center (m)(20,10,1.5) LNumber of multipaths (-)21 MPosition vector of depolarization mechanism (m) Randomly distributed inside the environment D sp Depolarization operator (-) Calculated using the distributions in [1] rMultipath length (m)|A-M|+|B-M| (θ T,φ T )DoD ( o ) Calculated based on the propagation scenario (θ R,φ R )DoA ( o ) [1] C. Oestges et. al., “Propagation modeling of MIMO Multipolarized Fixed Wireless Channels”, IEEE Transactions on Vehicular Technology, Vol. 53, No. 3, pp , May 2004.

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS MEG Results MEG differences are below 3.3 dB Mutual coupling among closely spaced elements causes antenna radiation efficiency reduction Average MEG value drops as the number of branches increases

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Envelope Correlation Coefficient Results All values are below 0.5

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS CDF of Normalized Received Power Strong mutual coupling leads to saturation behavior

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS EDG, MEAG and DG of the 5 MEA Systems Number of branches EDG (dB)MEAG (dB)DG (dB) The values for EDG and DG are calculated at 1% probability level Saturation behavior

UNIVERSITY OF PATRAS ELECTRICAL & COMPUTER ENG. DEPT. LABORATORY OF ELECTROMAGNETICS Conclusions The Diversity Performance Evaluation of compact MEA systems was performed using a new hybrid Electromagnetic-Discrete Multipath (EMDM) model having the following characteristics: describes the antennas using full wave analysis and the wireless channel using physical modeling requires a small number of input parameters can be implemented in any geometry based propagation scenario (e.g. a cluster based scenario) calculates separately the system’s capability to mitigate multipath fading (DG) and the capability to capture average power (MEAG)

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