Metamaterial Inspired Antenna Miniaturization for MIMO System Applications

Transcription

1 Forum for Electromagnetic Research Methods and Application Technologies (FERMAT) Metamaterial Inspired Antenna Miniaturization for MIMO System Applications By: Muhammad Umar Khan, Department of Electrical Engineering King Fahd University of Petroleum & Minerals December, 2014 Abstract : Fourth generation (4G) wireless communication standards have adopted multiple-input-multiple-output (MIMO) systems to cater for high data rate requirements. For a successful implementation of these standards, the antenna of MIMO systems is an important design consideration. The MIMO systems require that their antenna with multiple elements should have high port isolation and low correlation between it elements. The wireless devices, where these systems are implemented require that their antenna must be low-profile and fit within the enclosing of the device. Together, these restrictions make the design of antennas for the MIMO systems a challenging task. Antenna is still one of the largest parts of any communication device. A standard antenna dimension correspond to half wavelength of its operating frequency. Decreasing the size of antenna beyond this limit severely degrades its radiation characteristics. For MIMO systems, accommodating multiple antenna elements in a limited space is therefore a serious issue which require that the novel antenna miniaturization techniques be developed. These techniques should try to reach the best possible practical limit of small antennas while maintaining reasonable radiation characteristics. In this work, antennas for MIMO systems are designed for various standards between 0.7 GHz to 6 GHz. All the designed antennas are planar, low-profile and uses modified microstrip patch antennas (MPAs) as the elements. A metamaterial (MTM) inspired technique is proposed which uses the complementary split-ring resonator (CSRR) for MPA miniaturization. We first thoroughly investigate the miniaturization technique and then develop design procedures based on it. An 80% miniaturization in the patch area is achieved using the proposed method in the 700 MHz band and 65% miniaturization is achieved in the 5GHz band. The miniaturized MPA thus developed are used to design 2-element MIMO antenna systems in the lower LTE band, 4-element MIMO antenna systems in the ISM band and 8-element MIMO antenna systems in the WiFi band. All the designs are highly compact and conform to the dimensions of a standard wireless device. Keywords: Metamaterial, Inspired Antenna,Miniaturization, MIMO System Applications.

2 INTRODUCTION Design MIMO Antenna Systems 0.7 GHz 6 GHz Solutions for designing compact, planar and low-profile antennas for such MIMO Systems Special Emphasis to the miniaturization of planar antennas Antenna inside a Tablet 2

3 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 3

4 MOTIVATION Use of Mobile Devices is on the rise Market Forecast of Wireless Mobile Devices * (in millions) Market Forecasts Laptops UltraMobiles Tablets Mobile Phones Laptops Ultra Mobiles Tablets Mobile Phones * 4

5 MOTIVATION Applications in use Multi-point video conferencing HD video streaming Distant Learning Size 4 Mbps 10 Mbps 50 Mbps 2 hr HD Video 4.5 GB 2.3 hrs 57 min min Echo-diagram Study Time to download a file versus the speed * 4 GB 2.1 hrs 50 min 10 min Audio Book 110 MB 3.4 min 1.4 min 7 sec Telemedicine * 5

6 MOTIVATION 4G-LTE standards use MIMO systems to cater for high data rate requirements They can offer a theoretical 100 Mbps speed Practical Data rates offered by 3G and 4G Technologies * Downlink Uplink 3G 4 Mbps 1 Mbps 4G 10 Mbps 6-8 Mbps Antenna is an important design consideration for 4G systems * 6

7 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 7

8 MIMO SYSTEMS An important technical breakthrough towards achieving higher channel capacity in multipath environments Tx 0 Tx 1 Rx 0 Rx 1 Multiple antenna elements at both receiver and transmitter ends to improve the throughput of the communication system among others Tx N Rx N 8

9 MIMO SYSTEMS MIMO systems make use of the multipath environment and provide gains over a SISO Tx 0 1 Rx 0 counterpart, such as Diversity Gain Array Gain Multiplexing Gain Tx 1 1 Diversity Gain Rx 1 9 Due to conflicting demands of all these methods, MIMO Tx 0 1 Rx 0 systems cannot utilize all these advantages simultaneously. Tx 1 2 Rx 1 Multiplexing Gain 9 9

10 MIMO ANTENNA SYSTEMS Front-end of any wireless MIMO system (any modern handheld device) Devices using MIMO systems require that their antennas are low profile, fit in a limited space and cover several bands. The MIMO antenna system consists of several antenna elements of similar features arranged in such a way that they fit within the wireless device with reasonable performance A 3-element MIMO Antenna System * * 10

11 PERFORMANCE EVALUATION OF MIMO ANTENNA SYSTEM Conventional antenna performance metrics are not sufficient to describe and predict the performance of MIMO antenna system Some additional features are calculated to characterize the performance of MIMO antenna system A MIMO antenna system is evaluated based on 1. Reflection Coefficient & Isolation 2. Radiation Efficiency Γ = b i 2 a i 2 3. Radiation Patterns 4. Total Active Reflection Coefficient (TARC) 5. Correlation Coefficient 6. Mean Effective Gain (MEG) 7. Channel Capacity ρ e = [b]= S. [a] F 1 θ, φ F 2 θ, φ dω 2 F 1 θ, φ 2 dω F 2 θ, φ 2 dω 11

12 MIMO ANTENNA SYSTEM DESIGNS Initial work on MIMO antenna systems design appeared in 2005 * The work analyzed a standard array of 6 monopoles for performance in MIMO systems The work concluded that isolation between antenna elements of such a system greatly effect its performance High isolation between antenna elements is required to gain the anticipated benefits of a MIMO system Many designs were presented in literature from 2005 onwards Miniaturized antenna elements & high isolation between closely placed antenna elements are the main features sought by a MIMO antenna designer *K. Rosengren and P. Kildal, Radiation eciency, correlation, diversity gain and capacity of a six-monopole antenna array for a MIMO system : theory, simulation and measurement in reverberation chamber," IEE Proc. Microw. Antennas Propag., vol. 152, no. 1, pp. 7-16,

13 MIMO ANTENNA SYSTEMS DESIGNS MIMO antenna system designs presented in various Journals * * M. S. Sharawi, Printed Multi-Band MIMO Antenna Systems and their Performance Metrics, IEEE Antennas & Propagations Magazine, Vol. 55, No. 5, pp , Oct

14 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 14

15 WORK CONTRIBUTIONS 1. A systematic design Metamaterials(MTM)-inspired technique for the design of miniaturized MPA 2. Applying the Theory of Characteristic Modes to understand and explain the behavior of the proposed miniaturization technique 3. Design of MIMO Antenna Systems for various bands between 0.7 GHz 6 GHz using the proposed MTM-inspired MPAs as their elements 4. Characterization of the designed MIMO antenna systems in a real wireless indoor environment 5. An MTM-inspired isolation enhancement technique for the proposed MIMO antenna systems 15

16 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 16

17 MICROSTRIP PATCH ANTENNA (MPA) Well analyzed, widely used printed antenna Methods of Analysis Transmission-line model Cavity Model 3D radiation pattern of MPA Full wave methods f r = 1 2π εμ mπ h 2 + nπ L 2 + pπ W 2 A Microstrip patch antenna 17

18 ELECTRICALLY SMALL ANTENNAS (ESA) An antenna whose maximum dimension is less than λ 2π is called an ESA ESAs are evaluated based on their Q and radiation efficiency An ESA has a low bandwidth, high Q, and low radiation efficiency / gain Work McLean, Minimum Q 2 ka + 1 (ka) 3 Thal, (ka) 3 Gustafsson,2007 G 1 η 2(ka) 3 An antenna enclosed in Chu-sphere 18

19 MINIATURIZATION OF MPA MPA patch antenna can be miniaturized by Changing the effective wavelength Increasing the current path Several Techniques are used in Literature for MPA miniaturization Material Loading Folding & Shorting Reshaping \ Introducing Slots Modification of GP MTM inspired techniques A miniaturized circular Patch Antenna * * Saman Jahani, Jalil Rashed-Mohassel, and Mahmoud Shahabadi Miniaturization of Circular Patch Antennas Using MNG Metamaterials, IEEE Antennas & Wireless Propagation Letters, vol. 0, pp ,

20 SUMMARY Miniaturization Technique Material Loading Shorting & Folding Reshaping a Patch / Introducing Slots Features Advantages Disadvantages High dielectric substrates Ceramic Substrates Magnetodielectric substrates Shorting pins Shorting walls Folding Fractal Antenna Engineered conductors Slots in the patch High degree of miniaturization Easy design procedure Up to 4 times miniaturization Cost effective solution Up to 8 times miniaturization Can provide wider bandwidth Expensive materials Limited bandwidth No standard design procedure Complex antenna geometry Non-planar Complex antenna geometry No standard design procedure Modification in Ground Plane Slots in GP Use of DGS Up to 8 times miniaturization Planar & Simple geometry Low efficiency Increase back lobe level No standard design procedure Use of Metamaterials Use of ENG, MNG, DNG substrates Use of MTM-inspired techniques High degree of miniaturization Limited bandwidth Low efficiency Complex geometry No standard design procedure 20

21 CSRR LOADED MPA A patch antenna is miniaturized by etching out a complementary split-ring resonator (CSRR) underneath it The effect of various parameters of the CSRR on the resonant frequency are analyzed The Geometry of the proposed Miniaturized MPA 21

22 PARAMETRIC ANALYSIS Parametric studies to model the effect of CSRR dimensions radius r, width of ring w spacing between the rings s Reflection Coefficient (db) Variation of the width of CSRR rings "w" w=0.5mm w=0.7mm w=0.9mm w=1.1mm w=1.5mm Frequency (GHz) Change in the resonant frequency due to r 22

23 EQUIVALENT CIRCUIT MODEL Babinet s principle can be used to find the impedance of the CSRR The impedance of a structure is related to its complementary image by Z s Z c = η2 4 The single ring CSRR is a complementary image of the loop antenna The impedance of the loop antenna is related to its circumference Resistance curves for a loop Reactance curves for a loop 23

24 EQUIVALENT CIRCUIT MODEL Equivalent circuit model of the CSRR loaded MPA 24

25 DESIGN PROCEDURE Design a patch antenna with resonant frequency higher than the desired frequency Etch out a CSRR underneath the patch While tuning the CSRR, if the resonant frequency is lost, shift the feedline along the patch until the resonance is recovered. During all this process, make sure that the main radiator remains the patch. Simulate and note the resonant frequency Decrease r Increase w, s of the CSRR No Resonant frequency > desired frequency Yes Increase r Decrease w, s of the CSRR Finish 25

26 THEORY OF CHARACTERISTIC MODES Characteristic modes are the orthogonal current modes that can exist on a conducting body of arbitrary shape CM theory provides a solution to compute these modes numerically Currently, the theory is being used for systematic antenna design and analysis application 1968 : Garbacz 1971 : Harrington & Mutaz : Marta Cabedo Fabrés, Eva Antonino Daviu Theory Applications 26

27 THEORY OF CHARACTERISTICS MODES The relation between E-field and the J produced on conducting body is L J E i = 0 The surface current can be expanded as a sum of basis function J = a n J n n Defining Testing function W and taking inner product n a n L(J n ), W m = W m, E i Above equation in Matrix form I n Z mn = [V m ] An arbitrary shape conducting body S 27

28 THEORY OF CHARACTERISTICS MODES Using the symmetry of Generalized impedance matrix R = 1 2 X = 1 2j Z + Z Z Z Eigenvalue (λ n ) The matrix form an Eigenvalue equation X [J n ] = λ n R [J n ] Characteristic Currents (Jn) Modal Significance E n = jωa n j 1 ωεμ (. A n) Characteristic Angle Characteristic Fields (En) J = n a n J n 28

29 29.5 mm ANALYSIS OF MINIATURIZED MPA 38 mm MPA structure without excitation Eigenvalue for the first mode of the MPA structure 29

30 29.5 mm ANALYSIS OF MINIATURIZED MPA 38 mm CSRR loaded MPA structure without excitation Eigenvalue for the first mode of the CSRR loaded MPA structure 30

31 ANALYSIS OF MINIATURIZED MPA Characteristic current corresponding to the first mode 31

32 SUMMARY & COMPARISON Ref. Band BW Red. G or ɳ Tech. Structure [2] 900 MHz 10% 50% 6 dbi Material Loading Non-planar [25] 1.24 GHz 1% 90% - Material Loading Non-planar [4] 2.45 GHz 4% 75% 90% Shorting & Folding Non-planar [45] 935 MHz 0.3% 75% - Slots in Patch Planar [36] 2.45 GHz 34% 50% 70% Reshaping Patch Non-planar [51] 1.5 GHz 7% 90% - Modification of GP Planar [6] GHz 1.9% 77% 67% Modification of GP Planar [58] 2.45 GHz 0.4% 75% 28.1% MTM-inspired Non-planar [59] 700 MHz 0.5% 60% -7.9 dbi MTM-inspired Non-planar This Work 2.45 GHz* 2% 76.5% 30% MTM-inspired Planar 32

33 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 33

34 MIMO ANTENNA SYSTEM DESIGNS USING THE CSRR-LOADED MPA Using the CSRR-loaded MPAs, MIMO antenna systems of 2, 4 and 8 elements were designed for various bands between 0.7 GHz 6 GHz This included the antenna for LTE 700 MHz band, ISM 2.45 GHz band, and the WiFi 5 GHz band 34

35 4-ELEMENT MIMO ANTENNA SYSTEM FOR 2.4 GHZ BAND Fabricated 4-element MIMO antenna system (a) Top side, (b) Bottom side Geometry of the 4-element MIMO antenna system (a) Top side, (b) Bottom side M. S. Sharawi, M. U. Khan, A. B. Numan and D. N. Aloi, ``A CSRR loaded MIMO antenna system for ISM band operation", IEEE Transactions on Antenna and Propagation, vol. 61, no. 8, pp , Aug

36 4-ELEMENT MIMO ANTENNA SYSTEM FOR 2.4 GHZ BAND Minimum BW = 60 MHz Minimum Isolation = 10 db Reflection coefficient curves of the 4-element MIMO antenna system Measured isolation curves of the 4-element MIMO antenna system 36

37 4-ELEMENT MIMO ANTENNA SYSTEM FOR 2.4 GHZ BAND Current distribution of the 4- element MIMO antenna system when element, (a) 1 is active (Top side), (b) 3 is active (Top side), (c) 1 is active (Bottom side flipped ), (d) 3 is active (Bottom side flipped) 37

38 4-ELEMENT MIMO ANTENNA SYSTEM FOR 2.4 GHZ BAND Radiation patterns of the 4-element MIMO antenna system in the y-z plane. Radiation patterns of the 4-element MIMO antenna system in the x-z plane. Radiation pattern measurements conducted at an outdoor measurement facility at OU, USA. 38

39 4-ELEMENT MIMO ANTENNA SYSTEM FOR 2.4 GHZ BAND Antenna Element MEG, Efficiency & Correlation Coefficient MEG (XPD = 0 db) MEG (XPD = 6 db) % % % % Max. Correlation Coefficient 0.14 Radiation Efficiency 39

40 CHANNEL CAPACITY ESTIMATION The upper bound of channel capacity of a MIMO system can be evaluated using H matrix C = log 2 det I + ρ N HH bits/sec/hz It is of the form ; h 11 h 1N h N1 h NN 40

41 CHANNEL COEFFICIENT MATRIX The channel matrix can be evaluated by ; Measurements in the environment of interest Theoretical calculations based on the antenna radiation patterns and assumptions of the environment - Different models exists (e.g. Kronecker Model) - Models try to simplify the environment and use 2D radiation patterns 41

42 MEASUREMENT SETUP A 4 x 4 system MIMO system was implemented and measurements were carried for indoor LOS as well as NLOS case SDR platforms were used to implement the 4 x 4 MIMO System 4-element printed MIMO antenna were connected at both ends Standard Monopoles were also connected for the comparison 1) M. U. Khan, W. A. Al-Saud and M. S. Sharawi, ``Isolation Enhancement Effect on the Measured Channel Capacity of a Printed MIMO Antenna System", The 8th European Conference on Antennas and Propagation, The Hague, The Netherlands, April 6-11, ) M. U. Khan, W. A. Al-Saud and M. S. Sharawi, ``Channel Capacity Measurement of a 4- Element Printed MIMO Antenna System", The 8th German Microwave Conference, Aachen, March 10-12,

43 CHANNEL CAPACITY MEASUREMENT Rx 15 ft Tx Measurement Scenario in the LOS case 43

44 CHANNEL CAPACITY MEASUREMENT Rx 15 ft Tx 10 ft Measurement Scenario in the NLOS case 44

45 CHANNEL CAPACITY MEASUREMENT Channel estimation pulses were sent to measure the H matrix 1000 realizations were carried out to find average H matrix at a fixed location 25 realizations of H matrix was obtained by changing the location of Tx and Rx The H matrix was normalized to remove the first order statistics i-e path loss and to get the second order statistics i-e channel correlation 45

46 CHANNEL CAPACITY RESULTS Channel Capacity (Bits/sec/Hz) Printed 4-element MIMO 4 x 4 Monopole Ideal 4x4 MIMO SNR (db) Channel Capacity in the N- LOS environment 4-Element MIMO NLOS 8.9 bits/sec/hz LOS 7.1 bits/sec/hz Channel Capacity (Bits/sec/Hz) Printed 4-element MIMO 4 x 4 Monopole Ideal 4x4 MIMO SNR (db) 4 Monopoles 12.5 bits/sec/hz 10 bits/sec/hz Channel Capacity in the LOS environment 46

47 d = 0.5 mm 4 & 8-ELEMENT MIMO ANTENNA SYSTEM FOR 5 GHZ BAND 4 11 mm 8 mm 3 s = 0.5 mm 5 mm 5 mm w =0.25 mm r = 2.5 mm mm 100 mm 100 mm 50 mm Fabricated 4-element MIMO antenna system (a) Top side, (b) Bottom side (a) 50 mm Geometry of the 4-element MIMO antenna system (a) Top side, (b) Bottom side (b) 47

48 d = 0.5 mm 4 & 8-ELEMENT MIMO ANTENNA SYSTEM FOR 5 GHZ BAND 8 mm s = 0.5 mm 11 mm 8 7 w =0.25 mm r = 2.5 mm mm 100 mm mm 5 mm mm 50 mm 30 mm 50 mm Fabricated 8-element MIMO antenna system (a) Top side, (b) Bottom side (a) (b) Geometry of the 8-element MIMO antenna system (a) Top side, (b) Bottom side M. U. Khan and M. S. Sharawi, A compact 8-element MIMO antenna system for ac WLAN applications, in the proceedings of International Workshop on Antenna Technology (iwat 13), Karlsruhe, Germany, March 4-6,

49 4 & 8-ELEMENT MIMO ANTENNA SYSTEM FOR 5 GHZ BAND Reflection coefficient of the 4- element MIMO Antenna System Measured Isolation for the 4- element MIMO Antenna System 49

50 4 & 8-ELEMENT MIMO ANTENNA SYSTEM FOR 5 GHZ BAND Reflection coefficient of the 4- element MIMO Antenna System 2D Radiation patterns of the 4- Element MIMO Antenna System measured at 5.04 GHz, (a) x-z plane, (b) y-z plane [Element 1 = Black, Element 2 =Pink, Element 3 = Blue, Element 4 = Red] 50

51 2-ELEMENT MULTI-BAND MIMO ANTENNA SYSTEM COVERING LTE 700 MHZ BAND Fabricated 2-element MIMO Antenna system (a) Top side, (b) Bottom side Geometry of the 2-element MIMO Antenna system (a) Top side, (b) Bottom side M. U. Khan and M. S. Sharawi, ``A 2 x 1 multi-band MIMO antenna system consisting of miniaturized patch elements", Microwave & Optical Technology Letters, Vol. 56, No. 6, pp , Jun

52 2-ELEMENT MULTI-BAND MIMO ANTENNA SYSTEM COVERING LTE 700 MHZ BAND S-parameters of the 2-element MIMO Antenna system 52

53 2-ELEMENT MULTI-BAND MIMO ANTENNA SYSTEM COVERING LTE 700 MHZ BAND Measured gain pattern of the proposed MIMO antenna system (a) 750~MHz x-z plane, (b) 750~MHz y-z plane, (c) 1170~MHz x-z plane, (d) 1170~MHz y-z plane, (e) 1700~MHz x-z plane, (f) 1700~MHz y-z plane, (g) 2350~MHz x-z plane, (h) 2350~MHz y-z plane Anechoic Chamber for the antenna measurements at KAUST, KSA. 53

54 2-ELEMENT MULTI-BAND MIMO ANTENNA SYSTEM COVERING LTE 700 MHZ BAND Band (MHz) MEG Element 1 (db) MEG, Efficiency & Correlation Coefficient MEG Element 2 (db) Radiation Efficiency Element 1 Radiation Efficiency Element % 28% % 14% % 21% % 19% 0.01 Correlation Coefficient 54

55 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 55

56 MTM-INSPIRED ISOLATION ENHANCEMENT FOR MIMO ANTENNA SYSTEMS Isolation enhancement is also an important topic of research in the design of MIMO antenna systems A 10 db isolation was achieved by antenna element placement An MTM-inspired isolation enhancement technique is also proposed which gave at least 4 db enhancement It uses a split ring resonator to increase the isolation 56

57 SPLIT-RING RESONATOR (SRR) SRR is a resonant structure and behaves as LC resonator [3],[4] The resonant frequency of SRR depends on its dimensions [A]J. B. Pendry, A. J. Holden, D. J. Robbins and W. J. Stewart, Magnetism from Conductors and Enhanced Nonlinear Phenomena, IEEE Trans. Microw. Theory Tech., vol. 47, no. 8, pp , Nov [B] J. D. Baena, J. Bonache, F. Martin, R. M. Sillero, F. Falcone, T. Lopetegi, M. A. G. Laso, J. Garcia-Garcia, I. Gil, M. F. Portillo, and M. Sorolla, Equivalent-circuit models for split-ring resonators and complementary split-ring resonators coupled to planar transmission lines, IEEE Trans. Microw. Theory Tech., vol. 53, no. 4, pp , Apr [C] A. Pradeep, S. Mridula, and P. Mohanan, Design of an Edged-Coupled Dual-Ring Split-Ring Resonator, IEEE Antennas Propag. Mag., vol. 53, no. 4, pp ,

58 4-ELEMENT MIMO ANTENNA WITH IMPROVED ISOLATION The isolation was improved by placing the SRR between patch elements The dimensions of the SRR corresponded to the resonant frequency of 2.45 GHz Outer radius r Width w Spacing s Split d Geometry of the 4-element MIMO antenna with improved isolation 5.8 mm 0.6 mm 1.2 mm 1 mm 58

59 4-ELEMENT MIMO ANTENNA WITH IMPROVED ISOLATION 0 db S 11 S 22 S 33 S 44 S 12 S 14, S 23 S 13, S S Frequency (GHz) Geometry of the 4-element MIMO antenna with improved isolation Fabricated 4-element MIMO antenna with improved isolation Peak Gain Bandwidth Minimum Isolation dbi 60 MHz -18 db 59

60 4-ELEMENT MIMO ANTENNA WITH IMPROVED ISOLATION Surface current density on the 4-element MIMO antenna with single element excitation Surface current density on the 4-element MIMO antenna with improved isolation 60

61 ISOLATION IMPROVEMENT IN OTHER BANDS Outer radius r Width w Spacing s Split d 2.4 mm 0.3 mm 0.7 mm 0.5 mm 0-5 db S 11 S 22 S 33 S 44 S 12 S 14, S S 13, S 24 S Frequency (GHz) S-Parameters of the MIMO Antenna with improved isolation operating in 5 GHz band Geometry of the 4-element MIMO (Operating in the 5 GHz band) antenna with improved isolation 61

62 DESIGN PROCEDURE FOR THE ISOLATION TECHNIQUE Design the Miniaturized patch elements based MIMO antenna for the desired band Calculate the dimensions of the SRR for the resonant frequency of antenna Place the SRR between the radiating edges of patch antenna M. U. Khan, and M. S. Sharawi, ``Isolation Improvement Using an MTM Inspired Structure with a Patch Based MIMO Antenna System", The 8th European Conference on Antennas and Propagation, The Hague, The Netherlands, April 6-11,

63 SUMMARY & COMPARISON Ref Band of Operation Elements Type No. Size (mm 3 ) Minimum Isolation (db) [87] 2.45, 5.4, 5.8 GHz Printed Monopoles Structure 2 90 x 35 x Planar [123] 2.3 GHz PIFA 2 38 x 28 x Planar [83] 2 GHz Printed Monopoles 4 95 x 60 x Planar [110] 2.65 GHz MPA 3 90 x 120 x 1 28 Planar [11] 2.45 GHz PIFA x 120 x 18 - Non-Planar [126] 5 GHz Printed Yagi-Uda 3 55 x 48 x Planar [96] 5.2 GHz Dipoles x 210 x Non-Planar [127] 750 MHz PIFA x 55 x 4 12 Non-Planar [103] 700 MHz PIFA 2 40 x 90 x 5 13 Non-Planar [102] 700 MHz PIFA 2 95 x 60 x 9 20 Non-Planar Proposed GHz MPA x 50 x Planar Proposed 2 5 GHz MPA x 50 x Planar Proposed MHz, 1.17, 1.7, 2.35 GHz MPA x 60 x Planar 63

64 OUTLINE Motivation MIMO Systems & Antennas Work Contributions Proposed Miniaturized MPA MIMO Antenna Systems using Proposed MPA Elements Isolation Enhancement in the Proposed MIMO Antenna Systems Conclusions & Future Work 64

65 CONCLUSIONS A novel CSRR-loaded miniaturized MPA design technique has been developed The technique provides more than 80% miniaturization in the lower LTE band, 65% miniaturization in the 5 GHz WiFi band The technique is simple to implement, planar, and do not use any lumped components 65

66 CONCLUSIONS The proposed MPA were used to design the MIMO antenna systems operating in different bands and their performance was fully analyzed System level measurements were carried out to access the performance of the designed antennas An MTM-inspired isolation enhancement technique was also proposed and applied 66

67 FUTURE WORK Improving the radiation efficiency / BW of the CSRRloaded MPA Come up with a controlled design methodology for multi-band, efficient loaded antennas utilizing the theory of CM. Analyzing the optimal antenna element placement for a particular structure 67

68 PUBLICATIONS : JOURNAL PUBLICATIONS 1) M. U. Khan, M. S. Sharawi and R. Mittra ``Microstrip Patch Antenna Miniaturization Techniques : A Review", accepted in IET Microwave, Antennas & Propagation, December ) M. U. Khan and M. S. Sharawi, ``A dual band microstrip annular slot based MIMO antenna system", Microwave & Optical Technology Letters, Vol. 57, No. 2, pp , Feb ) M. U. Khan and M. S. Sharawi, ``A 2 x 1 multi-band MIMO antenna system consisting of miniaturized patch elements", Microwave & Optical Technology Letters, Vol. 56, No. 6, pp , Jun ) M. S. Sharawi, M. U. Khan, A. B. Numan and D. N. Aloi, ``A CSRR loaded MIMO antenna system for ISM band operation", IEEE Transactions on Antenna and Propagation, vol. 61, no. 8, pp , Aug ) M. S. Sharawi, A. B. Numan, M. U. Khan and D. N. Aloi, ``A dual-element dual-band MIMO antenna system with enhanced Isolation for Mobile Terminals", IEEE Antennas and Wireless Propagation Letters, vol. 11, pp , PATENT ``CSRR Loaded Multiple-Input-Multiple-Output (MIMO) Antenna System," Mohammad S. Sharawi, Muhammad U. Khan and Ahmed B. Numan (KFUPM, KSA), Filed on Sep to USPO, Patent Pending.

69 PUBLICATIONS : CONFERENCE PUBLICATIONS 1) M. U. Khan, and M. S. Sharawi, ``Annular Slot Based Printed MIMO Antenna System Design", 2014 IEEE International Symposium on Antenna and Propagation, Memphis, TN, USA, July 6-12, ) M. U. Khan, W. A. Al-Saud and M. S. Sharawi, ``Isolation Enhancement Effect on the Measured Channel Capacity of a Printed MIMO Antenna System", The 8th European Conference on Antennas and Propagation, The Hague, The Netherlands, April 6-11, ) M. U. Khan, and M. S. Sharawi, ``Isolation Improvement Using an MTM Inspired Structure with a Patch Based MIMO Antenna System", The 8th European Conference on Antennas and Propagation, The Hague, The Netherlands, April 6-11, ) M. U. Khan, W. A. Al-Saud and M. S. Sharawi, ``Channel Capacity Measurement of a 4-Element Printed MIMO Antenna System", The 8th German Microwave Conference, Aachen, March 10-12, ) M. U. Khan, M. S. Sharawi, and D. A. Aloi, A multi-band 2 x 1 MIMO antenna system consisting of CSRR loaded patch elements, in the proceedings of 2013 IEEE International Symposium on Antenna and Propagation, Florida, USA, July 7-13, ) M. U. Khan and M. S. Sharawi, Channel capacity analysis of a novel printed MIMO antenna system in wireless mobile environment, in the proceedings of 2013 IEEE International Symposium on Antenna and Propagation, Florida, USA, July 7-13, ) M. U. Khan, M. S. Sharawi, A. Steffes, and D. N. Aloi, A 4-element MIMO antenna system loaded with CSRRs and patch antenna elements, in the proceedings of 7th European Conference on Antenna and Propagation (EuCAP 2013), Gothenburg, Sweden, April 8-12, ) M. U. Khan and M. S. Sharawi, A compact 8-element MIMO antenna system for ac WLAN applications, in the proceedings of International Workshop on Antenna Technology (iwat 13), Karlsruhe, Germany, March 4-6, 2013.

70 THANK YOU! Q & A?