Forum for Electromagnetic Research Methods and ... Inspired Antenna Miniaturization for MIMO System Applications By: Muhammad Umar Khan, Department of Electrical Engineering King Fahd

Metamaterial Inspired Antenna Miniaturization for MIMO System Applications

By:Muhammad Umar Khan, Department of Electrical EngineeringKing 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.

Forum for Electromagnetic Research Methods and Application Technologies (FERMAT)

Dissertation Defense (Dec,2014)

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

2

Antenna inside a Tablet


OUTLINE

3

• Motivation

• Work Contributions

• Proposed Miniaturized MPA

• Isolation Enhancement in the Proposed MIMO Antenna Systems

• MIMO Systems & Antennas

• MIMO Antenna Systems using Proposed MPA Elements

• Conclusions & Future Work

• Motivation


MOTIVATION

• Use of Mobile Devices is on the rise

4

2013 2014 2017

(in millions)

Laptops 315 302 271

UltraMobiles 23 38 96

Tablets 197 265 468

Mobile Phones

1875 1949 2129

Market Forecast of Wireless Mobile Devices *

Market Forecasts

Laptops Ultra Mobiles Tablets Mobile Phones

* http://www.gartner.com


MOTIVATION

• Applications in

use

– Multi-point video

conferencing

– HD video

streaming

– Distant Learning

– Telemedicine

5

Size 4 Mbps 10 Mbps 50 Mbps

2 hr HD Video 4.5 GB 2.3 hrs 57 min 11. 4 min

Echo-diagram Study

4 GB 2.1 hrs 50 min 10 min

Audio Book 110 MB 3.4 min 1.4 min 7 sec

Time to download a file versus the speed *




MOTIVATION

Downlink Uplink

3G 4 Mbps 1 Mbps

4G 10 Mbps 6-8 Mbps

6

• 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 *

• Antenna is an important design consideration for 4G

systems


OUTLINE

7

• Motivation








MIMO SYSTEMS

• An important technical

breakthrough towards

achieving higher channel

capacity in multipath

environments

• Multiple antenna elements

at both receiver and

transmitter ends to

improve the throughput of

the communication

system among others

8

Tx 0

Tx 1

Tx N

Rx 0

Rx 1

Rx N


MIMO SYSTEMS

• MIMO systems make use of the

multipath environment and

provide gains over a SISO

counterpart, such as

– Diversity Gain

– Array Gain

– Multiplexing Gain

• Due to conflicting demands of

all these methods, MIMO

systems cannot utilize all these

advantages simultaneously.

9

1

1

Diversity Gain

Rx 0

Rx 1

Tx 0

Tx 1

Tx 0

Tx 1

9

Multiplexing Gain

Tx 0

Tx 1

Rx 0

Rx 1

1

2

9


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

10

* http://www.robaid.com/

A 3-element 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

3. Radiation Patterns

4. Total Active Reflection Coefficient (TARC)

5. Correlation Coefficient

6. Mean Effective Gain (MEG)

7. Channel Capacity

PERFORMANCE EVALUATION OF MIMO

ANTENNA SYSTEM

11

Γ = 𝑏𝑖2

𝑎𝑖2

[b]= 𝑆 . [𝑎]

𝜌𝑒 = 𝐹1 𝜃, 𝜙 ∗ 𝐹2 𝜃, 𝜙 𝑑Ω

2

𝐹1 𝜃, 𝜙2𝑑Ω 𝐹2 𝜃, 𝜙

2𝑑Ω


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

12

*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, 2005.

Dissertation Defense (Dec,2014)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. 218-232, Oct. 2013


OUTLINE

14

• Motivation








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


OUTLINE

16

• Motivation








MICROSTRIP PATCH ANTENNA (MPA)

17

A Microstrip patch antenna

• Well analyzed, widely used

printed antenna

• Methods of Analysis

– Transmission-line model

– Cavity Model

– Full wave methods

𝑓𝑟 =1

2𝜋 𝜀𝜇

𝑚𝜋

ℎ

2

+𝑛𝜋

𝐿

2

+𝑝𝜋

𝑊

2

3D radiation pattern of MPA


ELECTRICALLY SMALL ANTENNAS

(ESA)

• An antenna whose maximum dimension

is less than𝜆

2𝜋is 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

18

An antenna enclosed in Chu-sphere

Work Minimum Q

McLean, 1996 1

2

2

𝑘𝑎+1

(𝑘𝑎)3

Thal, 2006 1

(𝑘𝑎)3

Gustafsson ,2007 𝐺

𝜂

1

2(𝑘𝑎)3


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

19

* Saman Jahani, Jalil Rashed-Mohassel, and Mahmoud Shahabadi “Miniaturization of Circular Patch Antennas Using MNG Metamaterials,” IEEE Antennas & Wireless Propagation Letters, vol. 0, pp. 1194-1196, 2010.

A miniaturized circular Patch Antenna *


SUMMARY

MiniaturizationTechnique

Features Advantages Disadvantages

Material Loading • High dielectric substrates• Ceramic Substrates• Magnetodielectric substrates

• High degree of miniaturization

• Easy design procedure

• Expensive materials• Limited bandwidth

Shorting & Folding • Shorting pins• Shorting walls• Folding

• Up to 4 times miniaturization

• Cost effective solution

• No standard design procedure• Complex antenna geometry• Non-planar

Reshaping a Patch / Introducing Slots

• Fractal Antenna• Engineered conductors• Slots in the patch


• Can provide wider bandwidth

• Complex antenna geometry• No standard design procedure

Modification in Ground Plane

• Slots in GP• Use of DGS


• 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


CSRR LOADED MPA

21

• 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


PARAMETRIC ANALYSIS

22

2.4 2.42 2.44 2.46 2.48 2.5 2.52 2.54 2.56 2.58 2.6-40

-35

-30

-25

-20

-15

-10

-5

0

5

Frequency (GHz)

Reflection C

oeffic

ient (d

B)

Variation of the width of CSRR rings "w"

w=0.5mm

w=0.7mm

w=0.9mm

w=1.1mm

w=1.5mm

• Parametric studies

to model the effect of

CSRR dimensions

– radius ‘r’,

– width of ring ‘w’

– spacing between the

rings ‘s’

22

Change in the resonant frequency due to ‘r’


EQUIVALENT CIRCUIT MODEL

23

• 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

𝒁𝒔𝒁𝒄 =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


EQUIVALENT CIRCUIT MODEL

24

Equivalent circuit model of the CSRR loaded MPA


DESIGN PROCEDURE

25

Design a patch antenna with resonant frequency higher than

the desired frequency

Etch out a CSRR underneath the patch

Simulate and note the resonant frequency

Increase ‘r’Decrease ‘w’, ‘s’ of

the CSRR

Resonant frequency

> desired

frequency

Decrease ‘r’Increase ‘w’, ‘s’ of

the CSRR

No Yes

Finish

• While tuning the CSRR, if the resonantfrequency is lost, shift the feedline along thepatch until the resonance is recovered.

• During all this process, make sure that the mainradiator remains the patch.


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

26

1968 : Garbacz

1971 : Harrington & Mutaz

2007-08 : Marta Cabedo Fabrés , Eva

Antonino Daviu

Theory

Applications


THEORY OF CHARACTERISTICS MODES

𝐿 𝐽 − 𝐸𝑖 = 0

𝐽 =

𝑛

𝑎𝑛𝐽𝑛

𝑛 𝑎𝑛 𝐿(𝐽𝑛),𝑊𝑚 = 𝑊𝑚, 𝐸𝑖

𝐼𝑛 𝑍𝑚𝑛 = [𝑉𝑚]

27

An arbitrary shape conducting body ‘S’

The relation between E-field and the J produced on conducting body is

The surface current can be expanded as a sum of basis function

Defining Testing function W and taking inner product

Above equation in Matrix form


THEORY OF CHARACTERISTICS MODES

• Eigenvalue (𝜆𝑛 )

• Characteristic Currents (Jn)

• Modal Significance

• Characteristic Angle

• Characteristic Fields (En)

28

𝑅 =1

2𝑍 + 𝑍∗

𝑋 =1

2𝑗𝑍 − 𝑍∗

𝑋 [𝐽𝑛] = 𝜆𝑛 𝑅 [𝐽𝑛]

Using the symmetry of Generalized impedance matrix

The matrix form an Eigenvalue equation

𝐽 =

𝑛

𝑎𝑛𝐽𝑛

𝐸𝑛 = −𝑗𝜔𝐴𝑛 − 𝑗1

𝜔𝜀𝜇𝛻(𝛻. 𝐴𝑛)


ANALYSIS OF MINIATURIZED MPA

29

29

.5 m

m

38 mm

MPA structure without excitation

Eigenvalue for the first mode of the MPA structure



30

29

.5 m

m

38 mm

CSRR loaded MPA structure without excitation

Eigenvalue for the first mode of the CSRR loaded MPA structure



31

Characteristic current corresponding to the first mode


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] 2.635 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

ThisWork

2.45 GHz* 2% 76.5% 30% MTM-inspired Planar

32


OUTLINE

33

• Motivation








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


4-ELEMENT MIMO ANTENNA SYSTEM

FOR 2.4 GHZ BAND

35

Geometry of the 4-element MIMO antenna system(a) Top side, (b) Bottom side

Fabricated 4-element MIMO antenna system(a) Top side, (b) Bottom side

M. S. Sharawi, M. U. Khan, A. B. Numan and D. N. Aloi, `À CSRR loaded MIMO antenna system for ISM band operation", IEEE Transactions on Antenna and Propagation, vol. 61, no. 8, pp. 4265-4274, Aug. 2013.



FOR 2.4 GHZ BAND

36

Reflection coefficient curves of the 4-element MIMO antenna system

Measured isolation curves of the 4-element MIMO antenna system

• Minimum BW = 60 MHz• Minimum Isolation = 10 dB



FOR 2.4 GHZ BAND

37

Current distribution of the 4-element MIMO antenna systemwhen element , (a) 1 is active (Topside) , (b) 3 is active (Top side), (c)1 is active (Bottom side flipped ) ,(d) 3 is active (Bottom sideflipped)



FOR 2.4 GHZ BAND

38

Radiation patterns of the 4-element MIMO antenna system in the x-z plane.

Radiation patterns of the 4-element MIMO antenna system in the y-z plane.

Radiation pattern measurements conducted at

an outdoor measurement facility at OU, USA.



FOR 2.4 GHZ BAND

39

Antenna Element

MEG (XPD = 0 dB)

MEG(XPD = 6 dB)

Radiation Efficiency

1 -5. 44 -5. 43 29%

2 -5.65 -5.64 29%

3 -8.00 -8.00 29%

4 -8.96 -8.96 29%

Max. Correlation Coefficient 0.14

MEG, Efficiency & Correlation Coefficient


CHANNEL CAPACITY ESTIMATION

• The upper bound of channel capacity of a MIMO system

can be evaluated using ‘H’ matrix

• It is of the form ;

ℎ11 ⋯ ℎ1𝑁⋮ ⋱ ⋮ℎ𝑁1 ⋯ ℎ𝑁𝑁

𝐶 = 𝑙𝑜𝑔2 𝑑𝑒𝑡 𝐼 +𝜌

𝑁𝐻𝐻∗ bits/sec/Hz

40


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


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

42

1) M. U. Khan , W. A. Al-Saud and M. S. Sharawi, `Ìsolation 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, 2014.

2) 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, 2014


CHANNEL CAPACITY MEASUREMENT

43

Rx

Tx

15 ft

Measurement Scenario in the LOS case


Rx

Tx

15 ft

10 ft

Measurement Scenario in the NLOS case




• 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


CHANNEL CAPACITY RESULTS

46

0 5 10 15 20 25 300

5

10

15

20

25

30

35

SNR (dB)

Channel C

apacity (

Bits/s

ec/H

z)

Printed 4-element MIMO

4 x 4 Monopole

Ideal 4x4 MIMO

Channel Capacity in the LOS environment

0 5 10 15 20 25 300

5

10

15

20

25

30

35

SNR (dB)

Channel C

apacity (

Bits/s

ec/H

z)

Printed 4-element MIMO

4 x 4 Monopole

Ideal 4x4 MIMO

Channel Capacity in the N-LOS environment

4-ElementMIMO

4 Monopoles

NLOS 8.9 bits/sec/Hz

12.5bits/sec/Hz

LOS 7.1 bits/sec/Hz

10 bits/sec/Hz


4 & 8-ELEMENT MIMO ANTENNA

SYSTEM FOR 5 GHZ BAND

47



10

0 m

m

11

mm

8 mm

5 mm

5 m

m

1.5 mm

50

mm

50 mm

10

0 m

m

‘w’=0.25

mm

‘s’ = 0.5

mm

‘r’ = 2.5

mm

‘d’

= 0

.5 m

m

12

34

(a) (b)




10

0 m

m

11

mm

8 mm

5 mm

50 mm

1.5 mm

5 m

m

30

mm

50 mm

10

0 m

m

12

34

56

78 ‘w’=0.25

mm

‘s’ = 0.5 mm

‘r’ = 2.5 mm

‘d’

= 0

.5 m

m

(a) (b)

48



M. U. Khan and M. S. Sharawi, “A compact 8-element MIMO antenna system for 802.11ac WLAN applications”, in the proceedings of International Workshop on Antenna Technology (iWAT 13), Karlsruhe, Germany, March 4-6, 2013.




49

Reflection coefficient of the 4-element MIMO Antenna System

Measured Isolation for the 4-element MIMO Antenna System




50

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]


2-ELEMENT MULTI-BAND MIMO ANTENNA

SYSTEM COVERING LTE 700 MHZ BAND

51

Geometry of the 2-element MIMO Antenna system (a) Top side, (b) Bottom side

Fabricated 2-element MIMO Antenna system (a) Top side, (b) Bottom side

M. U. Khan and M. S. Sharawi, `À 2 x 1 multi-band MIMO antenna system consisting of miniaturized patch elements", Microwave & Optical Technology Letters, Vol. 56, No. 6, pp. 1371-1375, Jun. 2014.




S-parameters of the 2-element MIMO Antenna system




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.




Band (MHz)

MEG Element 1 (dB)

MEG Element 2 (dB)

Radiation Efficiency Element 1

Radiation Efficiency Element 2

Correlation Coefficient

750 -5.88 -5.67 28% 28% 0.05

1170 -7.05 -6.68 13% 14% 0.05

1700 -5.28 -5.35 21% 21% 0.01

2350 -13.13 -11.27 19% 19% 0.01

MEG, Efficiency & Correlation Coefficient


OUTLINE

55

• Motivation








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


SPLIT-RING RESONATOR (SRR)

57

• 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. 2075-2084, Nov. 1999.[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. 14511461, Apr. 2005[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. 45-54, 2011.


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

58

Outer radius ‘r’ 5.8 mm

Width ‘w’ 0.6 mm

Spacing ‘s’ 1.2 mm

Split ‘d’ 1 mm

Geometry of the 4-element MIMO antenna with improved isolation



IMPROVED ISOLATION

59

2.3 2.35 2.4 2.45 2.5 2.55 2.6 2.65 2.7-30

-25

-20

-15

-10

-5

0

Frequency (GHz)

dB

S11

S22

S33

S44

S12

S14

, S23

S13

, S24

S34

Geometry of the 4-element MIMO antenna with improved isolation

Fabricated 4-element MIMO antenna with improved isolation

Peak Gain - 0.5 dBi

Bandwidth 60 MHz

Minimum Isolation -18 dB



IMPROVED ISOLATION

60

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


ISOLATION IMPROVEMENT IN OTHER

BANDS

61

Outer radius ‘r’ 2.4 mm

Width ‘w’ 0.3 mm

Spacing ‘s’ 0.7 mm

Split ‘d’ 0.5 mm

Geometry of the 4-element MIMO (Operating in the 5 GHz band) antenna

with improved isolation4.8 4.85 4.9 4.95 5 5.05 5.1 5.15 5.2

-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency (GHz)

dB

S11

S22

S33

S44

S12

S14

, S23

S13

, S24

S34

S-Parameters of the MIMO Antenna with improved isolation operating in 5 GHz band


DESIGN PROCEDURE FOR THE

ISOLATION TECHNIQUE

62

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, `Ìsolation 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, 2014.


SUMMARY & COMPARISON

Ref Band of Operation Elements Type No. Size (𝒎𝒎𝟑) Minimum Isolation (dB)

Structure

[87] 2.45, 5.4, 5.8 GHz Printed Monopoles

2 90 x 35 x 0.8 10 Planar

[123] 2.3 GHz PIFA 2 38 x 28 x 1.6 20 Planar

[83] 2 GHz Printed Monopoles

4 95 x 60 x 0.8 11.5 Planar

[110] 2.65 GHz MPA 3 90 x 120 x 1 28 Planar

[11] 2.45 GHz PIFA 2 120 x 120 x 18 - Non-Planar

[126] 5 GHz Printed Yagi-Uda 3 55 x 48 x 1.28 - Planar

[96] 5.2 GHz Dipoles 2 270 x 210 x 10 20 Non-Planar

[127] 750 MHz PIFA 2 110 x 55 x 4 12 Non-Planar



Proposed 1 2.45 GHz MPA 4 100 x 50 x 0.8 -18 Planar

Proposed 2 5 GHz MPA 8 100 x 50 x 0.8 -15 Planar

Proposed 3 750 MHz, 1.17, 1.7, 2.35 GHz

MPA 2 120 x 60 x 0.8 -10 Planar63


OUTLINE

64

• Motivation








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


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


FUTURE WORK

• Improving the radiation efficiency / BW of the CSRR-

loaded 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

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 2014.

2) M. U. Khan and M. S. Sharawi, `À dual band microstrip annular slot based MIMO antenna system", Microwave & Optical

Technology Letters, Vol. 57, No. 2, pp. 360 - 364, Feb. 2015.

3) M. U. Khan and M. S. Sharawi, `À 2 x 1 multi-band MIMO antenna system consisting of miniaturized patch elements",

Microwave & Optical Technology Letters, Vol. 56, No. 6, pp. 1371-1375, Jun. 2014.

4) M. S. Sharawi, M. U. Khan, A. B. Numan and D. N. Aloi, `À CSRR loaded MIMO antenna system for ISM band operation",

IEEE Transactions on Antenna and Propagation, vol. 61, no. 8, pp. 4265-4274, Aug. 2013.

5) M. S. Sharawi, A. B. Numan, M. U. Khan and D. N. Aloi, `À dual-element dual-band MIMO antenna system with enhanced

Isolation for Mobile Terminals", IEEE Antennas and Wireless Propagation Letters, vol. 11, pp. 1006-1009, 2012.

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. 2012 to USPO, Patent Pending.

PUBLICATIONS :

CONFERENCE PUBLICATIONS

1) M. U. Khan , and M. S. Sharawi, `Ànnular Slot Based Printed MIMO Antenna System Design", 2014 IEEE International

Symposium on Antenna and Propagation, Memphis, TN, USA, July 6-12, 2014.

2) M. U. Khan , W. A. Al-Saud and M. S. Sharawi, `Ìsolation 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, 2014.

3) M. U. Khan , and M. S. Sharawi, `Ìsolation 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,

2014.

4) 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, 2014.

5) 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,

2013.

6) 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, 2013.

7) 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, 2013.

8) M. U. Khan and M. S. Sharawi, “A compact 8-element MIMO antenna system for 802.11ac WLAN applications”, in the

proceedings of International Workshop on Antenna Technology (iWAT 13), Karlsruhe, Germany, March 4-6, 2013.

THANK YOU !

Q & A ?

Documents

Forum for Electromagnetic Research Methods and ... Inspired Antenna Miniaturization for MIMO System Applications By: Muhammad Umar Khan, Department of Electrical Engineering King Fahd