Introduction to Metamaterials:Application to Communications

Systems Design

Ignacio Gil Departament d’Enginyeria Electrònica

Universitat Politècnica de Catalunya, Spain

I.Gil

Outline

Motivation

Metamaterials Introduction

Applications

Filtering

Couplers, Diplexers, Dividers

Design Example: RF-MEMS Metamaterials

Conclusions

I.Gil

Outline

Motivation

Metamaterials Introduction

Applications

Filtering

Couplers, Diplexers, Dividers

Design Example: RF-MEMS Metamaterials

Conclusions

I.Gil

Motivation

RF Front-EndIF stages and

signal processing

I.Gil

Motivation

TechnologiesMicromachining

RF MEMSMCM-D

New Design Strategies

Electromagnetic BandGaps METAMATERIALS

Devices isolation

Filtering

Espurious supression

Miniaturization

Radiation leakage inhibition

Tunability

Efficiency

Low-losses

High-Q

Si Technology

Reconfigurable devices

Multi-metal structures

I.Gil

Motivation

Metamaterials Introduction

Applications

Filtering

Couplers, Diplexers, Dividers

Design Example: RF-MEMS Metamaterials

Conclusions

Outline

I.Gil

MetamaterialsArtificially fabricated material, based on periodic (or quasi-periodic)structures, with singular and controllable electromagnetic properties, notpresent sometimes in natural media.

Types • Electromagnetic and Photonic Cristals (EBG, PBG)• Effective media with negative index (LHM, ENG, MNG)

EBG LHM

Period ∼ λg

Bragg Effect

Bragg Condition

pπβ =

Woodpile structureε, μ simultaneiusly negativePeriod << λg (miniaturization)

I.Gil

MetamaterialsEffective media metamaterialsArtificial structures with controllable magnetic permeability and/or dielectricpermittivity.

ε

μRHM

n, β >0, n∈ℜ(dielectric materials)

LHMn, β <0, n∈ℜ(no existing in nature)

MNGn, β ∈ℑ

(Ferrimagnetic materials)

ENGn, β ∈ℑ

(Plasmas, metals at optical frequencies)

Medios opacos

• Transparent medium• Backward waves• Negative refraction index !!!!!!!• Left Handed Media (LHM)

I.Gil

Metamaterials

Maxwell EquationstB

cxE

∂∂

−=∇1

tD

cxH

∂∂

=∇1

HB μ=

ED ε=

Monocrhomatic plane wave Hc

xE μωβ =

Ec

xH εωβ −=

ExHcSπ4

=

Poynting Vector

E

H

β

β

E

H

RHM LHM

S S

Left Handed Materials– LHM (properties)

vg

vp

vg

vp

I.Gil

Metamaterials

Doppler effect

Cherenkov radiation

Negative refraction

Curved lenses Flat lenses

V. Veselago, Sov. Phys. Usp, 1968

Left Handed Materials– LHM (properties)

I.Gil

MetamaterialsSynthesis of LHM (superposition of two artificial media)

E

βH

SRR - Pendryε < 0 μ < 0

d << λg

2

2

1ωω

ε p−= 22

2

1o

Fωωωμ−

−=

F: Fractional area.

ωo: resonance frequency

μ < 0 ⇔ ωo < ω < ωo/(1-F)1/2

Plasma

frequency

First synthesis of a LHM – Smith, 2000

I.Gil

Excited by an axial magnetic field

Current loops between the rings

LC tank behaviour

pulo CrC ⋅⋅= πspul

o LCr ⋅⋅=π

ω 2

SRR

22

2

1o

Fωωωμ−

−=F: fractional area

μ<0 ⇔ ωo < ω < ωo/(1-F)1/2

Metamaterials

Medium with μ < 0

I.Gil

Metamaterials

COMPLEMENTARY

CSRR

SRR

Medium with ε < 0

Excited by an axial electric field

CSRRs can be placed in the ground plane of amicrostrip line.

fSRR ≈ fCSRR

Complementary Split Rings Resonator (CSRR)

First resonant particle with negative permittivity

I.Gil

Metamaterials

I.Gil

Metamaterials

f

S(2,1)

fp

fo

SRRs

wires

BACKWARD WAVE PROPAGATION

Ek S

H

SRRs μ < 0

INDUCTORS ε < 0

SUPERPOSITION

LHM MEDIUM

I.Gil

-50

-40

-30

-20

-10

0

0 2 4 6 8 10 12

Frequency (GHz)

S(1,

1), S

(2,1

) (dB

)

S(1,1)

S(2,1)

• Good frequency selectivity

• Small dimensions

• Out of band rejection > 25dB

IL ≈ 3.5dBsBW ≈ 0.6GHz

Arlon εr=2.43 ; h=0.49mm

1st LHM planar structure based on SRRs

F. Martin et al., APL, 2004

Metamaterials

I.Gil

Metamaterials

S(2,1)

fp

fo

CSRRs

gaps

CSRRs ε < 0

GAPS μ < 0

f

BACKWARD WAVE PROPAGATION

Ek S

H

SUPERPOSITION

LHM MEDIUM

I.Gil

Metamaterials

-40

-30

-20

-10

0

0 1 2 3 4 5 6

Frequency (GHz)

S(1,

1), S

(2,1

) (dB

)

IL ≈ 4dBsBW ≈ 0.4GHz

2Cg 2Cg

F. Falcone et al., PRL, 2004

I.Gil

Outline

Motivation

Metamaterials Introduction

ApplicationsFiltering

Couplers, Diplexers, Dividers

Design Example: RF-MEMS Metamaterials

Conclusions

I.Gil

Applications: Narrow Band Pass Filters

Bonache et al., Micr. & Opt. Tech. Lett., 2005

Falcone et al., Phys. Rev. Lett., 2004

Bonache. et al., IEEE Trans. Micr. Theo.Tech., 2006

I.Gil

Applications: Ultra Wide Band Pass Filters

Bonache et al., Micr. & Opt. Tech. Lett., 2005

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Applications: Improved Stop Band Filter

García-García. et al., IEEE Micr.Trans. Theo. Tech., 2005

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Applications: Tunable Filters

μ<0

I. Gil et al., Electronics Letters, 2004

VLSRR

Tunable BW

Infineon BB833

9pF-0.75pF (0V-28V)

I.Gil

Applications: Tunable Filters(a)

(b)

(a)

(b)Measurement

Electric simulations(with losses) Tuning

range>30%

I. Gil et al., IEEE-Micr. Trans.Theo. Tech., June 2006

I.Gil

0,5 1,0 1,5 2,0

-50

-40

-30

-20

-10

0

S11

S21

S P

aram

eter

s (d

B)

Frequency (GHz)

S51 S41 S21 S31 S11 S21 Simulation S11 Simulation

Jarauta et al., Micr. & Opt. Tech. Lett., 2006

M. Gil et al., PIERS, 2006

(2,1)S

(3,1)S(1,1)S

(3,2)S

J. Bonache et al., Elec. Lett., 2006

Applications: Couplers, Diplexers, Dividers

I.Gil

Outline

Motivation

Metamaterials Introduction

Applications

Filtering

Couplers, Diplexers, Dividers

Design Example: RF-MEMS Metamaterials

Conclusions

I.Gil

Tunable Metamaterials

1-D tunable metamaterials structures implemented inmicrostrip technology by using VLSRR

Significant losses due to varactor-metal junction resistance

Low quality factor, Q~10-30

RF-MEMS Metamaterials

I.Gil

CSRR+RF-MEMS CPW Unit Cell

CSRR

c=d=10μm

l=480μm ; w=130 μm

CPW

W=150μm ; G=30μm

RF-MEMS bridge

B=80μm ; b=100μm

H=290μm ; h=40μm

RF-MEMS modifies the electrical characteristics of CSRR (fo)

I.Gil

CSRR+RF-MEMS CPW Simulation

4-stage periodic device

50Ω CPW structure

Agilent Momentum

Coplanar mode

Mesh frequency=100GHz

Mesh density=20cells/λ

Device lenght: 2780μm

Distance between CSRR: 220μm

No mechanical effects

Up-state: MEMS_h=2μm

Down-state: MEMS_h=0.5μm

I.Gil

CSRR+RF-MEMS CPW Simulation

fo at Q-band: 39.2-49.2GHz

Tuning Range: ~20%

Rejection Level: IL<-50dB

No losses simulation

Down-state

Up-state

Up-state

Down-state

I.Gil

CSRR+RF-MEMS CPW Technology

Stripped-down RF-MEMS technology

3 lithographic steps

Al layer sputter-deposited and patterned on AF45 glass substrate(CPW structure)

Sacrificial photoresist layer (anchoring regions of the MEMS)

Al layer deposited (sacrifial layer removal)

Electrically floating bridge anchored directly on the substratein holes of the CPW ground planes

I.Gil

CSRR+RF-MEMS CPW Technology

Down-state: bridge only contacts the centre of CPW strip

Native Al oxide as interposer to prevent DC shorts

Al layer thickness: tAl=1μm

AF45 substrate: εr=5.9; h=650μm

Photoresist Layer: tPh=3μm

I.Gil

(a)

(b)

Actuation Voltage: 0-17V

fo at Q-band: 39-48GHz

Tuning Range: ~20%

Rejection Level: IL<-40dB

Good losses level (<-3dB)

CSRR+RF-MEMS CPW Experimental

I.Gil

Simulation vs Experimental

(a) (b)

Good agreement

Approximation validated

I. Gil et al., Electronics Letters, 2008

I.Gil

Motivation

Metamaterials Introduction

Applications

Filtering

Couplers, Diplexers, Dividers

Design Example: RF-MEMS Metamaterials

Conclusions

Outline

I.Gil

Conclusions

Metamaterials: Microwave engineering solution in order toachieve compact and miniaturized devices with asignificant performance improvement

Applications: Filtering, couplers, diplexers, dividers, etc

Performance:

Filtering: BPF:high selectivity ; UWBPF ; RPF: high rejection

Tunable devices: Tuning range~20%, IL<-40dB, high-Q (low losses)

Future work: RF-MEMS Band pass frequency response(ε,μ<0) , electrical modelling

Thanks for your attention!

Questions??

Introduction to Metamaterials:Application to Communications

Systems Design