From Maxwell s Equations to Modern Communication Antenna Marvels: An Amazing Journey of Novel Designs Yahya Rahmat-Samii Professor & Past Chairman Electrical Engineering Department U of California Los Angeles (UCLA) U.S.A. email: rahmat@ee.ucla.edu http://www.ee.ucla.edu/antlab
Potential Approaches for Miniaturization High Dielectric Constant Double Negative Material Low Profile using EBG Folding Antenna Structure Structure Profiling, Fractal, etc. Incorporation of Switches Hybridizations of Above Stored Energy Utilization Many aspects of these will be also touched upon in this talk.
Dual Band Patch Measured Results: Pixel Approach 0.0 5.0 S11 (db) 10.0 15.0 MoM Model FDTD Model Measured Prototype 20.0 1.0 2.0 3.0 4.0 5.0 Frequency (GHz) Measured results agree with MoM and FDTD simulations
PSO/FDTD in Broadband Patch Antenna Design: Parameter Approach ws L L s P s E-Shape Antenna 50 0 w L/2 x f 31% bandwidth Convergence Measurement Results Average fitness at the current iteration g best up to the current iteration Wide Band Design Dual-frequency Design 48-5 46 Fitness Value 44 42 Return Loss (db) -10-15 Antenna II 40 38 100 200 300 400 500 600 700 800 900 1000 The N th Iteration -20 Antenna I -25 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 Frequency (GHz)
Keyboard Influence Investigation Measurement Results No keyboard 90 0 120 0
MIMO Arrays Design and System Testing Directional Omnidirectional Array Configurations UCLA True MIMO Testbed (David Brown and Michael Fitz) Testing of designed antennas in real system environment Evaluation of system capacity as a function of antenna characteristics and array topology
UCLA Miniature MIMO Arrays
Tri-Band PIFA 0-5 PIFA 2 Slot PIFA 1 Tri-band PIFA using J-shaped and quarter wavelength slots. Reflection coefficient (db) -10-15 -20 2.45GHz 5.25GHz 5.75GHz -25 Measured Calculated -30 2 3 4 5 6 7 f (GHz) Calculated and measured reflection coefficient of the tri-band PIFA. Adding a quarter wavelength slot generates the third resonant frequency. Although, the small PIFA couples with the quarter wavelength slot, these two higher frequency bands can be brought as closely as desired.
Fractal Antennas and MIMO Properties of Fractal Antennas that potentially benefit antenna design: Space filling property to miniaturize wire and patch antennas Self-similarity to design multiband antennas Space filling ability Self-similarity Packaging 4 fractal elements in the same space as 3 standards UCLA MIMO
Reconfigurable Antennas: Patch Antennas Patch Slot Switch Ground Plane LHCP/RHCP diversity (2) (1) Dual frequency operation Dual band CP performance
Reconfigurable Dual-Frequency Dual-CP Antenna for Wireless Communications 0-2 -4 Measurement Switch - on Switch - off Operational Mechanism: Current Flow Feed Point Return Loss (db) -6-8 -10-12 Simulation -14-16 Switch off, Mesurement Switch off, Simulation -18 Switch on, Mesurement Switch on, Simulation -20 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 Frequency (GHz) y z x Switch-off, LHCP Φx is π/2 ahead Switch-on, RHCP Φ-y is π/2 ahead 300 330 30 60 300 330 0 30 60 MEMS switches can be used for low loss operations. 270 240-10dB 0dB -30dB -20dB 90 120 270 240-20dB -10dB 0dB -30dB 90 120 210 150 180 f=4 38GHz LHCP φ=0(deg) f=4.38ghz, LHCP, φ=0 210 150 180 f=4.38ghz,lhcp,φ=90(deg) f=4.38ghz, LHCP, φ=90
Meta-Materials ( Beyond the nature; none existing in the nature) Double Negative Materials (Left-handed) ε < 0 µ < 0 1960 s & 2000 s Optics Electromagnetic Bandgap Structures (EBG) 2000 s Microwave Soft & Hard Artificial complex ground planes QRP Γ = 90 phase AMC Γ = 0 phase PBG Passive Filters Components EBG - Antenna FSS 1990 s 1940 s 1995 s 1970 s
Wire antennas near PEC and PMC/EBG surfaces S11 Low profile PEC PEC PMC PMC/EBG Vertical wire antenna Horizontal wire antenna Vertical wire antenna Horizontal wire antenna
Very Low Profile Electric Antenna (< λ/30) Various Antennas on Artificial Complex Ground Plane Patch element Patch array Bent monopole Low profile curl CP dipole Surface wave antenna
Miniaturized Microstrip Patch Antennas-I: Patch Antenna on the High Dielectric and Thick Substrate x z y space waves Higher Dielectric Constant Substrates: Smaller Elements MMIC Fabrication surface waves Narrower Bandwidths t ε eff =10.20 diffraction Enhance Surface Waves Thicker Substrates: Wider Bandwidths Enhance more the Surface Waves High dielectric and thick substrate increases the surface waves and causes pattern degradation from the diffraction/scattering of the substrates modes at the finite substrate s edges.
Miniaturized Microstrip Patch Antennas-II: Performance of the Patch Antenna on the Thin/Thick High Dielectric Substrate Thin Substrate (t=0.032λ 0, BW=1.4%) t ε eff =10.20 y (cm) 35.0 30.0 25.0 20.0 15.0 90 60 30 Z 0 5 0-5 -10 30 60 90 X,Y E-plane H-plane 10.0 3λ 0 3λ 0 Substrate 5.0 120 120 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 x (cm) 150 180 150 E db Return Loss S 11 E (db) 20.0 40.0 60.0 80.0 0.0 Thick Substrate (t=0.059λ 0, BW=4.3%) S 11 (db) 5.0 10.0 15.0 20.0 y (cm) 40.0 35.0 30.0 25.0 20.0 15.0 10.0 90 60 30 Z 0 5 0-5 -10 30 60 90 X,Y E-plane H-plane 25.0 30.0 1.0 1.5 2.0 2.5 3.0 frequency (GHz) conventional thin substrate conventional thick substrate PBG substrate effective dielectric substrate 5.0 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 x (cm) 20.0 40.0 60.0 80.0 E (db) 120 120 150 150 180 E db Pattern bifurcation!
Miniaturized Microstrip Patch Antennas-III: EBG and Effective Dielectric in Suppressing the Surface Waves (TM z ) EBG EBG Substrate r=0.45a, a/λ 0 =0.35 r a y (cm) 40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 x (cm) 90 60 120 30 150 Z 0 5 0-5 -10 180 30 150 60 120 90 E-plane H-plane X,Y E db 20.0 40.0 60.0 80.0 E (db) Thick Substrate (t=0.059λ 0, BW=4.3%) High Performance Radiation Pattern with improved Bandwidth No Pattern bifurcation!
Universities must be considered as vital players in creating new and visionary concepts for future missions. ucla antenna lab UCLA Antenna Laboratory in co-operation with other institutions is advancing miniaturized antenna design concepts and developments for modern communications applications. We look forward to working with you for novel designs. Towards Miniaturization