Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our Privacy Policy and User Agreement for details.

Successfully reported this slideshow.

Like this presentation? Why not share!

No Downloads

Total views

6,316

On SlideShare

0

From Embeds

0

Number of Embeds

27

Shares

0

Downloads

640

Comments

0

Likes

4

No embeds

No notes for slide

- 1. Left-Handed Metamaterials for Microwave Engineering Applications Department of Electrical Engineering UCLA
- 2. Outline • Left-Handed Metamaterial Introduction Resonant approach Transmission line approach • Composite Right/Left-Handed Metamaterial • Metamaterial-Based Microwave Devices Dominant leaky-wave antenna Small, resonant backward wave antennas Dual-band hybrid coupler Negative refractive index flat lens • Future Trends • Summary
- 3. What is a Left-Handed Metamaterial? μ (Permeability) re conventional fle plasma d ct e cte (RH) fra d wire structure air air re nt ε < 0, μ > 0 ε > 0, μ > 0 ide n = + εμ inc No transmission ε (Permittivity) LHMs ferrites ε < 0, μ < 0 split rings structure air air ε > 0, μ < 0 n = − εμ No transmission 1967: Veselago speculates about the possibility of LHMs and discusses their properties.
- 4. What is a Left-Handed Metamaterial? Veselago’s Conclusions • Simultaneous negative permittivity (-ε) and permeability (-μ). • Reversal of Snell’s Law (negative index of refraction), Doppler Effect, and Cerenkov Effect. • Electric field, Magnetic field, and Wavevector of electromagnetic wave in a LHM form a left-handed triad. • LHMs support backward waves: anti-parallel group and phase velocity. • Artificial effectively homogenous structure: metamaterial.
- 5. Rectangular Waveguide Filled with LHM → Pin k backward wave (vp = -vg) ε>0, μ>0 → k → → ε<0, μ<0 k S LH Triad ε>0, μ>0 → S Pout → S HFSS simulation using effective medium [1] naturally occurring LH material has not yet been discovered
- 6. LHM – Resonant Approach • 1967: LHM were first proposed by Russian Physicist Victor Veselago • 2001: LHM realized based on split ring resonators - Resonant Approach towards LHMs [2]. SRR metal wire SRR-based LHM unit-cell SRR: at resonance provides μ<0 metal wire: provides ε<0 • SRR-based metamaterials only exhibit LH properties at resonance - inherently narrow-band and lossy. • SRR-based LHMs are bulky - not practical for microwave engineering applications.
- 7. LHM – Transmission Line Approach • Backward wave transmission line can form a non-resonant LHM [3]-[4]. • Transmission Line Approach is based on the dual of a conventional transmission line. Series capacitance (CL) and shunt CL CL CL inductance (LL) combination supports a fundamental backward wave. LL LL −1 β= Perfect LH transmission line ω C L LL • Perfect LH transmission line not resonant dependent - low-loss and broad-band performance. • However, perfect LH transmission line is not possible due to unavoidable parasitic right- handed (RH) effects occurring with physical realization.
- 8. Transmission Line Approach PRH TL LR PLH TL CL ... CR ... ... LL . .. 1 β PRH = ω CR LR β PLH = − ω CL LL ω ω −βc +βc −βc +βc β β
- 9. Composite Right/Left-Handed Metamaterial ω = −βc ω ω = + βc 0 0 CL LR CR LL CRLH RH β = s(ω ) ω 2C R LR + 1 ⎛L C ⎞ − ⎜ R + R ⎟, ω 2C L LL ⎜ LL C L ⎟ β ⎝ ⎠ • Low frequencies: supports ⎧ − 1 if ω < min(ω se , ω sh ) ⎫ backward wave s (ω ) = ⎨ ⎬, ⎩ + 1 if ω > max(ω se , ω sh )⎭ • High frequencies: supports forward where wave 1 1 ωse = and ω sh = • Two cases C L LR C R LL Unbalanced: ωse≠ ωsh Balanced: ωse= ωsh0
- 10. CRLH Metamaterial 1 2 3 N p Homogeneity Condition • Long wavelength regime CRLH TL • p < λg/4 0 L = N*p
- 11. CRLH Metamaterial – Physical Realization CL LR capacitors metal pads (provides RH effects) CR LL inductor via to gnd Composite right/left-handed (CRLH) unit-cell Lumped element implementation Distributed microstrip implementation Distributed microstrip implementation based based on interdigital capacitor on Sievenpiper mushroom structure [5]
- 12. CRLH – Implementation and Analysis Cascade periodic unit-cell to form one- or two-dimensional CRLH metamaterial TL. How to Characterize a CRLH Unit-Cell Propagation Constant – Dispersion Diagram Impedance – Bloch Diagram
- 13. Comparison of LHMs to PBGs and Filters Photonic Bandgap (PBG) Filters period Similarities Similarities • periodic structures • periodic structures • can be more than one-dimensional • based on low-pass/high-pass structures Differences Differences • PBGs have to be periodic; lattice period • Filters generally designed to meet magnitude determines scattering specifications; LHMs designed to meet both • PBG operated at frequencies where lattice magnitude and phase. period is multiple of λg/2; LHMs operated at • Node-to-node phase shifts of 180° required frequencies where period < λg/4. for filters. • LHMs can be one-, two-, or three- dimensional and are used as bulk “mediums.”
- 14. Dominant-Mode Leaky Wave Antenna
- 15. Leaky-Wave Antenna Theory Principle Conventional RH Leaky-Wave Antenna z ko (operated at higher-order mode) kz θ β source x θ = asin(β (ω ) k0 ) CRLH Leaky-Wave Antenna [6] (operated at dominant mode) kz2= ko2- β2 ω = − β c0 ω ω = + β c0 Characteristics: II III LH RH • Operating in leaky regions RAD. RAD. II : BACKWARD ( β < 0 ) CRLH I IV RH III : FORWARD ( β > 0 ) LH RH GUIDANCE GUIDANCE • BROADSIDE radiation ( β = 0 ) ω0 balanced case: vg(β = 0 ) ≠ 0 β • Fundamental mode
- 16. 1-D Dominant Mode Leaky-Wave Antenna 3-D Far-field Pattern for Several Frequencies Design Specifications fo = 2.4 GHz ZB = 50 Ω unit-cell P in frequency beam scanning Backfire – to – Endfire
- 17. Design Flow Unit-cell parameter – Design Guidelines Dispersion/Bloch Diagrams – Driven Mode Optimize unit-cell for specifications Cascade unit-cells to form CRLH transmission line Simulate CRLH transmission line • S-Parameters: matching • Far-field: fast-wave region for leaky-wave application
- 18. 1-D CRLH Unit-Cell (Interdigital) • Distributed unit-cell p series capacitance provided by interdigital capacitor shunt inductance provided from shorted stub w shunt capacitance from top metal to ground plane series inductance from current on interdigital capacitor ls lc Variables Initial Design Final Design unit-cell period p 12.3 mm 11.4 mm stub length ls 10.0 mm 10.9 mm stub width ws 1.00 mm 1.00 mm via interdigital finger length lc 10.5 mm 10.2 mm interdigital finger width wc 0.30 mm 0.30 mm spacing between fingers S 0.20 mm 0.20 mm via radius r 0.12 mm 0.12 mm ws substrate height h 1.57 mm 1.57 mm substrate permittivity εr 2.2 2.2
- 19. 1-D CRLH Unit-Cell Design Guidelines* For 2-D space scanning, we need to design a balanced (ωse = ωsh) CRLH unit- cell so that there is a seamless transition from LH to RH operation. 1. Choose center frequency, fo, which 5. Set the number of fingers, N, to 8 or 10. represents broadside radiation. (fo=2.4 Then determine required wc and S=2wc/3. GHz) N=10 chosen. w 2. Calculate width required to obtain Zo, set w wc ≈ ≈ 0.3 mm to this value. (w~5.0 mm) ⎛ 5N 2 ⎞ ⎜ − ⎟ ⎝ 3 3⎠ 3. Set stub width, ws, to 20% of w. (ws=1.0 mm) S = 0.2 mm 4. Set stub length (lsi=ls- w) to w; the electrical 6. Calculate length of interdigital finger. length of the stub has to be less than π/2. λg co lc ≈ ≈ ≈ 10.5 mm 8 8 fo ε r * Guidelines have been test on Rogers Duroid 5870 (er=2.33) and 5880 (er=2.2) for various substrate heights; for high permittivity substrate, the number of fingers should be reduced.
- 20. Dispersion/Bloch Diagram Extraction Design Specifications fo = 2.4 GHz ZB = 50 Ω extra section of mircostrip (5 mm each) Planar EM simulation ⎛ 1 − S11S 22 + S12 S 21 ⎞ βp = cos ⎜ ⎜ −1 ⎟ ⎟ S-Parameter extraction ⎝ 2 S 21 ⎠ 2 jZ o S 21 sin( β p ) ZB = (1 − S11 )(1 − S 22 ) − S 21S12
- 21. Dispersion Diagram Extraction Setup dispersion equation; this can be obtained directly from the S-parameters. ⎛ 1 − S11S 22 + S12 S 21 ⎞ βp = cos ⎜ ⎜ −1 ⎟ ⎟ ⎝ 2 S 21 ⎠ Go to Results > Create Report Then click on Output Variables
- 22. Dispersion Diagram Final Design Dispersion Diagram in Ansoft Designer fast-wave region beta < ko self resonance of interdigital capacitor slow-wave region e lin beta > ko air
- 23. Bloch Impedance Diagram Resulting Bloch Impedance Diagram in Ansoft Designer Re(ZB) Im(ZB) impedance (Ohm) LH RH fast-wave region fast-wave region
- 24. 10-Cell CRLH Leaky-Wave Antenna Port1 Port2 Return/Insertion Loss Insertion loss Return loss LH RH fast-wave region fast-wave region
- 25. 10-Cell CRLH Leaky-Wave Antenna Far-field Pattern for Several Frequencies Backward: f=1.95 GHz Broadside: f=2.35 GHz Forward: f=2.95 GHz
- 26. Small Metamaterial Antennas
- 27. Resonant Antenna Theory Conventional RH Patch Antenna CRLH Patch Antenna (treat as periodic, consisting of 2 RH “unit-cells”) (2 CRLH unit-cells) RH p CRLH p resonance condition RH p nπ CRLH p βn = 2p ω n = +1, +2, … n=+1 n = 0, ±1, ±2, … CRLH can have same half- n=+1 wavelength field distribution, but n=-1 at much lower frequency βp 0 π/2 π
- 28. 1.0 GHz CRLH n=-1 Antenna [7] for 4 unit-cells 5 Initial dispersion curve 4 Increase LL Frequency (GHz) Increase CL 3 Increase CL & LL 2 1 0 0 0.25 0.5 0.75 1 β∗ρ/π n= -1 mode is used h1 = 3.16 mm MIM 12.2 mm h2 = 0.254 mm Capacitance z y 15 mm x CPW stub h2 h1 1/19λ0 x 1/23λ0 x 1/88λ0 ground CWP feed
- 29. 1.0 GHz CRLH n=-1 Antenna [7] 0 -5 n = -3 top view Return Loss (dB) -10 n = -2 -15 -20 n = -1 measurement HFSS -25 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Frequency (GHz) E-copol (x-z plane) H-copol (y-z plane) back view E-xpol (x-z plane) H-xpol (y-z plane) 90 90 -5 -5 -10 135 -15 45 135 -10 45 -20 -15 -25 -20 -30 -25 -35 -30 -40 -45 -35 -50 -40 -35 -30 -25 -20 -15 -10 -5 -45 -40-35 -30 -25 -20 -15 -10 -5 180 0 180 0 225 315 225 315 270 270
- 30. CRLH n=0 Antenna (Monopolar) [8] Experimental Results 6 4.0 3.8 Frequency (GHz) Peak Gain (dBi) 4 3.6 3.4 2 ω 3.2 ω = − β c0 ω = + β c0 Exp. Peak Gain Exp. Resonant Frequency 0 3.0 2 4 6 # of unit-cells (N) n=0 points As N increases… CRLH • Gain increases. RH • Resonant frequency does not β change much.
- 31. CRLH n=0 Antenna (Monopolar) z z 0 0 330 30 330 30 0 0 -10 -10 300 60 300 60 -20 -20 -30 -30 z -40 270 90 x -40 270 90 y -30 x -30 -20 -20 -10 240 120 y -10 240 120 0 num. 0 num. 210 150 210 150 180 exp. 180 exp. x Θ, φ 0 0 330 30 330 30 0 0 -10 -10 300 60 300 60 -20 -20 -30 -30 -40 270 90 y -40 270 90 -30 -30 -20 -20 240 120 240 120 -10 -10 0 num. 0 x-z plane 210 150 210 150 180 exp. 180 y-z plane x-y plane Cross-Pol
- 32. Dual-/Multi-Band Metamaterial Components
- 33. Dual-Band Hybrid Coupler CRLH / CRLH hybrid [9] 360 1 CRLH 2 Conventional quadrature: 270 restricted to odd harmonics because only control on slope CRLH CRLH 180 4 CRLH 3 DC offset 90 Characteristics: f0 f1 f 2CRLH f 2conv = 3 f1 0 f • dual-band functionality for an arbitrary pair of frequencies f1, f2 −90 • principle: transition frequency (fo) −180 provides DC offset additional degree of freedom with respect to the −270 conv. RH phase slope CRLH • applications in multi-band systems −360
- 34. Dual-Band Hybrid Coupler Branch Line in Z0 out Experimental Results 0 2 -5 S-parameters (dB) LH TLs -10 Z0 Z0 Z0 -15 f2 = 1.89 S11 2 f1 S21 isolated out -20 S31 S41 -25 Band # 1: 0.92 GHz 0.6 0.8 1 1.2 1.4 1.6 1.8 2 frequency (GHz) Band # 2: 1.74 GHz
- 35. Negative Refractive Index Lenses
- 36. Negative Refractive Index Flat Lens [10] (nLH)sinθLH = (nRH) sinθRH Effective medium HFSS simulation RHM source (15 mm from interface) LHM θRH θLH RH medium LH medium refractive index nRH > 0 refractive index nLH < 0 Possibility of realizing a flat lens E-field magnitude RH medium RH medium 1 LH medium RH medium 2
- 37. Two-Dimensional CRLH Realization Based on Sievenpiper High-Impedance Structure patch LR C L p p CR LL via period of unit cell ground plane How to obtain dispersion characteristics? 1. Drivenmode Approach – Simple, quick, 1-D dispersion diagram. 2. Eigenmode Approach – Requires more processing time, accounts for mode coupling, 2-D dispersion diagram.
- 38. Unit-Cell Setup: Physical Details metal patch metal via radius = 0.12 mm t mm =4.8 height = 1.27 mm .8 mm t=4 h=1.27 mm z p= 5.0 mm mm .0 p =5 substrate parameters ground plane x y εr=10.2, tanδ=0.0023 Np/m * patch,via, and ground plane are assigned as copper.
- 39. Design Flow Unit-Cell Parameters – 1st Order Calculation Dispersion Characteristics Design Driven Mode Approach Verify Eigen Mode Approach • 1-D dispersion • 2-D dispersion • No mode coupling • Mode coupling Flat Lens Realization – Phase Matching HFSS Simulation Flat Lens • Symmetry Conditions: Reduce Simulation Time • Field Plots: Magnitude & Phase
- 40. Sievenpiper Unit-Cell: 1st Order Calculation distributed unit-cell equivalent circuit model fsh = 1/{2πsqrt(CR x LL)} series capacitance: CR ~ substrate permittivity x (patch area/substrate height) shunt inductance: LL ~ 0.2 x substrate height x ln[(2 x substrate height/via radis) – 1] * Left-handed mode will always occur below the shunt resonance (ωsh). Therefore, design dimensions such that wsh occurs at higher limit of frequency of interest. fsh ~ 5 GHz for the dimensions shown in previous slide.
- 41. Sievenpiper Unit-Cell: Driven Mode gap=0.2 mm • Modify unit-cell so that ports can be placed on it, while via keeping dimensions the same. Unit-cell becomes asymmetrical. Port 2 Port 1 • Run driven mode solution; set mesh frequency to ωsh from 1st order calculation. p=5.0 mm • Obtain S-parameters, use following expression to calculate propagation constant.
- 42. Sievenpiper Unit-Cell: Driven Mode 1-D dispersion diagram (from Port 1 to Port 2) e lin air right-handed mode band-gap left-handed mode
- 43. Eigenmode Solver: 2-D Dispersion Diagram z x y Γ Γ to X: px=0°, py=0°→180° X X to M: px=0°→180°, py=180° M M to Γ : px, py: 0°→180° • px: phase offset in x-direction • py: phase offset in y-direction Use Linked Boundary Conditions (LBCs) in HFSS to apply required phase shifts.
- 44. Sievenpiper Unit-Cell Setup Airbox and PML Setup 1. Create airbox1. 2. Select top face of airbox1 and assign PML. 3. Create airbox2. PML hPML=2.50 mm airbox2 hairbox1=8.00 mm airbox1 z physical dimensions shown in previous slide x y
- 45. Unit-Cell Setup: Linked Boundaries XZ - Planes YZ - Planes mx my sx z sy x y Slave BC: sx Slave BC: sy • phase delay: px (180 deg) • phase delay: py (0 deg)
- 46. Eigenmode 2-D Dispersion Diagram Plotted in Microsoft Excel 5 4 frequency (GHz) 3 2 1 0 Γ X M Γ
- 47. Dispersion Comparison: 1-D vs 2-D Solve 8 7 Drivenmode frequency (GHz) 6 Eigenmode (2D) 5 4 3 2 1 0 0 90 180 Beta*p (deg) Use drivenmode to quickly characterize/design, eigenmode to verify
- 48. Flat Lens – Physical Realization Entire circuit on Roger RT 6010 substrate with εr = 10.2 and h = 1.27mm PPWG 40.0 mm (n = +3.2) voltage source 15 mm refocus should occur at 3.8 GHz 50.0 mm LHM based on 21x10 mushroom unit-cells (n = -3.2 @ 3.8 GHz) 40.0 mm PPWG (n = +3.2) 125.0 mm
- 49. Flat Lens – Phase Matching Condition 5 phase match at 3.8 GHz frequency (GHz) 4 |βp| = 72 deg, |n|=3.2 3 X M 2 1 0 Γ0 30 60 90 120 150 180 210 240 270 βp (deg)
- 50. Flat Lens – Simulation Setup Entire circuit on Roger RT 62.5 mm 6010 substrate with 130.0 mm εr = 10.2 and h = 1.27mm voltage source C D PPWG (n = +3.2) 18.0 mm A B LHM based on 21x10 mushroom unit-cell (n = -3.2 @ 3.8 GHz) Boundary Conditions • Radiation boundary applied on Top and Side A, B, and C of air box. • Finite conductivity (Copper) applied on bottom of airbox, PPWG trace, and mushroom patches. • Symmetry boundary (perfect-H) applied to Side D to reduce problem size.
- 51. Flat Lens – Field Calculator for Phase To plot the E-field phase, the field calculator has to be used. • Go to HFSS > Fields > Calculator • Since the field is quasi-TEM, only the z-component of the E-field is required. Quantity > E Scal? > ScalarZ Vec? > VecZ Complex > CmplxPhase Mag Add, give name PhazeZ
- 52. Flat Lens – E-Field Plots (Ground Plane) field on ground plane @ f=3.75 GHz Magnitude Phase
- 53. Flat Lens – E-Field Plots (Above Structure) field on top of structure @ f=3.75 GHz (3.5 mm above top metal) Magnitude Phase
- 54. Flat Lens – Experimental Results f0 =3.79 GHz E-field magnitude Source Source E-field phase E-field measured ~ 3.5 mm above CRLH region
- 55. Future Trends
- 56. Applications & Research Metamaterial Multiple-Input-Multiple-Output (MIMO) Arrays for 802.11n Application [11] Active CRLH Metamaterials • High-gain leaky-wave antennas (embed amplifiers in unit-cell) [12] • Distributed amplifiers [13] Tunable Phase Shifters [14]
- 57. Implementations Nano-Metamaterials: optical frequency applications [15] Evanescent-Mode Metamaterials [16] 1-D LHM: cylindrical DRs in TE mode cutoff parallel plate waveguide (-ε) H-field Profile (TE01δ mode, -μ) Three-Dimensional Metamaterials [17]
- 58. Summary • Left-Handed Metamaterial Introduction Resonant approach Transmission line approach • Composite Right/Left-Handed Metamaterial • Metamaterial-Based Microwave Devices Dominant leaky-wave antenna Small, resonant backward wave antennas Dual-band hybrid coupler Negative refractive index flat lens • Future Trends
- 59. 1) References C. Caloz, C.C. Chang, and T. Itoh, “’Full-wave verification of the fundamental properties of left-handed materials (LHMs) in waveguide configurations,” J. App. Phys., vol. 90, no. 11, pp. 5483-5486, Dec. 2001. 2) R.A. Shelby, D.R. Smith, and S. Schultz, “Experimental verification of a negative index of refraction,” Science, vol. 292, pp. 77-79, Apr. 2001. 3) A. Lai, C. Caloz, and T. Itoh, “Composite right/left-handed transmission line metamaterials,” IEEE Microwave Magazine, Vol. 5, no. 3, pp. 34-50, Sep. 2004. 4) C. Caloz and T. Itoh, Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications, Wiley and IEEE Press, Hoboken, NJ, 2005. 5) D. Sievenpiper, L. Zhang, R.F.J. Broas, N.G. Alexopolous, and E. Yablonovitch, “High-impedance surface electromagnetic surfaces with a forbidden frequency band,” IEEE Trans. Microwave Theory Tech., vol. 47, no. 11, pp. 2059-2074, Nov. 1999. 6) L. Liu, C. Caloz, and T. Itoh, “Dominant mode (DM) leaky-wave antenna with backfire-to-endfire scanning capability,” Electron. Lett., vol. 38, no. 23. pp. 1414-1416, Nov. 2002. 7) C.J. Lee, K.M.K.H. Leong, and T. Itoh, “Design of resonant small antenna using composite right/left-handed transmission line,” Proc. IEEE Antennas and Propagation Society Int. Symp., Washington D.C., Jun. 2005. 8) A. Lai, K.M.K.H. Leong, and T. Itoh, “Infinite wavelength resonant antennas with monopolar radiation patterns based on periodic structures,” IEEE Trans. Antennas Propag., vol. 55, no. 3, pp. 868-876, Mar. 2007. 9) I. Lin, C. Caloz, and T. Itoh, “A branch-line coupler with two arbitrary operating frequencies using left-handed transmission lines,” IEEE-MTT Int. Symp. Dig., Philadelphia, PA, Jun. 2003, vol. 1, pp. 325–327. 10) A. Lai, “Theory and design of composite right/left-handed metamaterial-based microwave lenses," Master Thesis, Dept. E. E., UCLA, Los Angeles, CA, 2005. 11) Rayspan Corporation, http://www.rayspan.com 12) F. P. Casares-Miranda, C. Camacho Peñalosa, and C. Caloz, “High-gain active composite right/left-handed leaky-wave antenna,” IEEE Trans. Antennas Propag., vol. 54, no. 8, pp. 2292-2300, Aug. 2006. 13) J. Mata-Conteras, T. M. Martìn-Guerrero, and C. Camacho-Peñalosa, “Distributed amplifiers with composite right/left-handed transmission lines,” Microwave Opt. Technol. Lett., vol. 48, no. 3, pp. 609-613, March 2006. 14) E.S. Ash, “Continuous phase shifter using ferroelectric varactors and composite right-left handed transmission lines,” Master Thesis, Dept. E.E., UCLA, Los Angeles, CA 2006. 15) V.A. Podolskiy, A.K. Sarychev, and V.M. Shalaev, “Plasmon modes in metal nanowires and left-handed materials,” J. Nonlin. Opt. Phys. Mat., vol. 11, no. 1, pp. 65-74, 2002. 16) T. Ueda, A. Lai, and T. Itoh, “Demonstration of negative refraction in a cutoff parallel-plate waveguide loaded with 2-D square lattice of dielectric resonators,” IEEE Trans. Microwave Theory Tech., vol. 55, no. 6, pp. 1280-1287, Jun. 2007. 17) M. Zedler, P. Russer, and C. Caloz, “Circuital and experimental demonstration of a 3D isotropic LH metamaterial based on the rotated TLM scheme,” IEEE-MTT Int'l Symp., Honolulu, HI, Jun. 2007.
- 60. Design Guide • Ansoft Designer: 1-D Leaky-Wave Antenna • Ansoft HFSS: Negative Refractive Index Flat Lens

No public clipboards found for this slide

Be the first to comment