Microwave Engineering Group

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Metamaterial Unit Cells for Filtering Applications

• Microwave Engineering Group
• CIMC, FTS, UNS

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Microwave Engineering Group
Dr Vesna Crnojevic-Bengin Group Leader
Mr Vasa Radonic Senior researcher
Dr Branka Jokanovic Associated member
MSc Nikolina Jankovic Researcher
MSc Srdan Pavic Researcher
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Current Projects

• METATEC - Metamaterial-Based Technology for
  Broadband Wireless Communications and RF
  Identification, EUREKA
• Dual-Band and Three-Band Metamaterial-Based
  Microwave Cirucuits and Antennas Devices for
  Modern Communication Systems, MNTR, Serbia
• EMMAT - Low-cost architectures for scanning,
  imaging, filtering and cloaking based on
  innovative electromagnetic structured materials,
  FP7 Marie Currie ITN
• MetaTera Metamaterial and Terahertz
  Technologies for Modern Wireless Systems, COST
  Action

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Outline

• Metamaterials (MTM)
• Effective media concept
• Characteristics, Applications
• Left-Handed (negative index) MTM
• Our research results
• Super-compact microwave filters
• Tunability
• Electronical reconfigurability
• Ongoing research
• Multi-band devices
• Frequency selective surfaces (FSS)
• Artificial magnetism at terahertz frequencies

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Metamaterials

• Why do we need them?
• What are they?
• How to make them?

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The Invisible Man
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EM Wave Material Interaction

• Maxwell equations describe wave propagation in a
  material
• A material is characterized by er i µr (nr, Zr)

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Existing Materials

• Relatively small set of values of er and µr
  (nr, Zr) exists in nature
• Material parameters limit practical designes

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Existing Problems

• Trade-off dimensions vs. performances

Antennas narrow beam with only one source
element? Solution ENZ material!
Microstrip resonators reduced length with small
losses? Solution EVL material!
METAMATERIALS !
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Definition

• Metamaterials are artificial structures made of
  sub-wavelength unit cells, designed to achieve
  advantageous and unusual electromagnetic
  properties.
• Size and periodicity of the unit cells ? ?g/10 ?
  effective media concept can be applied
• Effective parameters (er eff , µr eff, nr eff, Zr
  eff) can be made arbitrarily small or large, or
  even negative in a certain frequency range (LH
  MTM)

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Exotic Properties of LH MTMs

• Negative propagation constant, negative
  refractive index, negative phase velosity
• Reversed phenomena of classical physics (Doppler
  effect, Vavilov-Cerenkov radiation, Snells law,
  Lensing effect, Goss-Henchens effect)

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Application of MTMs

• Scanning
• Unexpected radiation phenomena (backward
  radiation, leaky waves, full scanning etc.)
• Imaging
• Sub-wavelength imaging (amplify evanescent
  waves), work below the refraction limit etc.
• Filtering
• Ultra-sharp filtering, super-compact design,
  multi-band operation
• Cloaking
• channeling of radiation around an object, to make
  both the object and cloaking material invisible

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How to Produce Negative ?r?

• Plasmons phenomena of excitation in metals
• Resonance of electron gas (plasma)
• Plasmon produces a dielectric function of the
  form
• Typically, fp is in the UV-range
• J. Pendry, 1996 fp8.2GHz

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How to Produce Negative ?r?

• J. Pendry, 1999 Split Ring Resonator, SRR

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Experimental Validation

• Smith, Shultz, et al. 2000.

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Design Approaches

• Resonant (SRR-approach)
• ? Narrow LH range
• ? Small attenuation
• Babinet principle CSRR
• Non-resonant (TL- approach)
• Dual to conventional TL
• ? Relatively high insertion loss
• ? Wide LH range

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Our Recent Results

• Resonant Approach to LH MTM Design

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Multiple SRR and Spiral Resonators

• Increased N ? size reduction, wider and deeper
  stop bands between first two harmonics, reduced
  efficiency of excitation (weaker coupling to the
  host microstrip)
• Size of CSR reduced more then 66 in comparison
  to CSRR, but CSRs suffer from high insertion
  losses.
• V. Crnojevic-Bengin, V. Radonic, B. Jokanovic,
  Left-Handed Microstrip Lines with Multiple
  Complementary Split-Ring and Spiral resonators,
  Microwave and Optical Technology Letters, John
  Willey, vol. 49 no. 6, juni 2007, pp 1391-1395

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Multiple SRR and Spiral Resonators

• V. Crnojevic-Bengin, V. Radonic, B. Jokanovic,
  Left-Handed Microstrip Lines with Multiple
  Complementary Split-Ring and Spiral resonators,
  Microwave and Optical Technology Letters, John
  Willey, vol. 49 no. 6, juni 2007, pp 1391-1395

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Fractal Geometries of CSRR

• SS CSRR dimensions ?g/20 x ?g/20
• 35 lower resonant frequency then CSRR
• Higher selectivity on both sides of the passband
• Wider and deeped stop band (second harmonic ?
  22dB)
• V. Crnojevic-Bengin, V. Radonic, B. Jokanovic,
  Fractal Geometries of Complementary Split-Ring
  Resonators, IEEE Transaction on Microwave Theory
  and Techniques, October 2008

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Multiple SS CSRR

• Different behavior due to specific fractal shape
• SS curve higher miniaturization then any other
  fractal or non-fractal geometry (44 lower
  resonant frequency )
• Successfull suppression of frequency bands at
  2fc1
• V. Crnojevic-Bengin, V. Radonic, B. Jokanovic,
  Fractal Geometries of Complementary Split-Ring
  Resonators, IEEE Transaction on Microwave Theory
  and Techniques, October 2008

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Our Recent Results

• Non-Resonant Approach to LH MTM Design

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Four Grounded Spirals - ForeS

• Dimensions ?g/13 x ?g/13, low insertion losses
  and fractional LH BW ? 30
• Large design flexibility small changes to the
  inner dimensions, result in resonant frequency
  tuning range ? 67
• Very good out-of-band performance second
  harmonic at more then 4fr1
• Electronicall reconfigurability (diodes at
  relevant positions) 27 resonant frequency
  tuning range, different in- and out-of-band
  performances
• B. Jokanovic, V. Crnojevic-Bengin, Novel
  left-handed transmission lines based on grounded
  spirals, Microwave and Optical Technology
  Letters, John Willey, Vol. 49, No. 10, oktobar
  2007, pp. 2561-2567

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ForeS Modifications

• Extremly compact, high-selectivity BPF
• 3rd order filter dimensons ?g/4 x ?g/15
• BW3dB3.7 at 1.63GHz, IL-3dB, att.?75dB
  (lower), ? 40dB (up to 2.6 fc1)
• B. Jokanovic, V. Crnojevic-Bengin, O.
  Boric-Lubecke, Miniature High Selectivity
  Filters Using Grounded Spiral Resonators,
  Electronics Letters

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Grounden Spiral Resonator

• II, III and IV order filters with dimensions
  ?g/12x?g/13, ?g/7x?g/14, ?g/4x?g/15
• Insertion loss 2dB - 3.5dB
• Very steep roll-off (att.?70dB at the lower edge
  and ?30dB at the upper edge of the pass band, up
  to 3fc1)
• B. Jokanovic, V. Crnojevic-Bengin, O.
  Boric-Lubecke, Miniature Lowloss Metamaterial
  Resonators Based on Grounded Spirals and Their
  Application in Filter Design, Springer NATO
  Science series books

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Grounded S-Spiral Resonator

• Resonator dimensions ?g/88 x ?g/48
• Considerably increased Q-factor
• Miniature 3rd order filter FBW2.8,
  out-of-band attenuation -65dB, both at the lower
  and at the higher stop band.

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Our Recent Results

• LH MTM Multi-Band Devices

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Dual-Band CRLH Concept

• Second operating frequency
• Harmonic - conventional dual-band devices
• Arbitrary - dual-band systems
• Phase-response curve of the CRLH TL
• DC offset additional degree of freedom?
  Arbitrary pair of frequencies for dual-band
  operation
• Applications
• Phase shifters,
• matching networks,
• baluns, etc.

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Grounded Patch Resonator

• Two times smaller then SRR
• Second harmonic at 3fr1 (2fr1 for SRR)
• Stronger out-of-band rejection
• V. Radonic, V. Crnojevic-Bengin, B. Jokanovic,
  Analysis of Metamaterial Unit Cells Based on
  Grounded Patch, Microwave Review, September 2008.

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MS Embedded Grounded Patch

• Reduced dimensions, increased coupling
• 4th order SBF dimensions ??g/3, att. ?30dB,
  BW3dB29.3
• V. Radonic, V. Crnojevic-Bengin, B. Jokanovic,
  Analysis of Metamaterial Unit Cells Based on
  Grounded Patch, Microwave Review, September 2008.

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Multi-Band Patch-Based Unit Cell

• Non-harmonic spectral allocations
• Three separately controled distinct passbands in
  non-harmonic relation
• V. Radonic, V. Crnojevic-Bengin, B. Jokanovic,
  Novel Left-Handed Unit Cell for Multi-Band
  Filtering Applications, EuMC 2008, Amsterdam,
  NL, October 2008.

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Multi-Band Patch-Based Unit Cell

• Very wide-band BPF
• IEEE 801.11a and HyperLanII systems
• IL-1dB, FBW3dB 39 at 5.2GHz
• V. Radonic, V. Crnojevic-Bengin, B. Jokanovic,
  Novel Left-Handed Unit Cell for Multi-Band
  Filtering Applications, EuMC 2008, Amsterdam,
  NL, October 2008.

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Current Research

• Multi-Band Devices
• Frequency selective surfaces (FSS)
• Artificial magnetism at terahertz frequencies

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FSS

• Two-dimensional arrangements of unit cells
• Multylayer structures
• Can be used as substrates or superstrates

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MTM-Based THz Passives

• No natural magnetic materials at THz
• Terahertz application gap
• ICT, medical, security, food, ...
• The goal to reduce losses, custom-tailor the
  dispersion and offer new functionalities at mm
  and THz frequencies.
• Photonics approach vs. microwave approach
• Investigation of high-frequency limits of
  different concepts and technologies
• Tunable and switchable MTMs
• Random MTMs

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Metamaterial Unit Cells for Filtering Applications

• Microwave Engineering Group
• CIMC, FTS, UNS
• bengin_at_uns.ns.ac.yu,
• vasarad_at_uns.ns.ac.yu