From Maxwell s Equations to Modern Communication Antenna Marvels: An Amazing Journey of Novel Designs

Transcription

1 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. rahmat@ee.ucla.edu

2 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.

3 Dual Band Patch Measured Results: Pixel Approach S11 (db) MoM Model FDTD Model Measured Prototype Frequency (GHz) Measured results agree with MoM and FDTD simulations

4 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 Fitness Value Return Loss (db) Antenna II The N th Iteration -20 Antenna I Frequency (GHz)

5 Keyboard Influence Investigation Measurement Results No keyboard

6 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

7 UCLA Miniature MIMO Arrays

8 Tri-Band PIFA 0-5 PIFA 2 Slot PIFA 1 Tri-band PIFA using J-shaped and quarter wavelength slots. Reflection coefficient (db) GHz 5.25GHz 5.75GHz -25 Measured Calculated 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.

9 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

10 Reconfigurable Antennas: Patch Antennas Patch Slot Switch Ground Plane LHCP/RHCP diversity (2) (1) Dual frequency operation Dual band CP performance

11 Reconfigurable Dual-Frequency Dual-CP Antenna for Wireless Communications Measurement Switch - on Switch - off Operational Mechanism: Current Flow Feed Point Return Loss (db) Simulation Switch off, Mesurement Switch off, Simulation -18 Switch on, Mesurement Switch on, Simulation Frequency (GHz) y z x Switch-off, LHCP Φx is π/2 ahead Switch-on, RHCP Φ-y is π/2 ahead MEMS switches can be used for low loss operations dB 0dB -30dB -20dB dB -10dB 0dB -30dB f=4 38GHz LHCP φ=0(deg) f=4.38ghz, LHCP, φ= f=4.38ghz,lhcp,φ=90(deg) f=4.38ghz, LHCP, φ=90

12 Meta-Materials ( Beyond the nature; none existing in the nature) Double Negative Materials (Left-handed) ε < 0 µ < 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

13 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

14 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

15 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.

16 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) Z X,Y E-plane H-plane λ 0 3λ 0 Substrate x (cm) E db Return Loss S 11 E (db) Thick Substrate (t=0.059λ 0, BW=4.3%) S 11 (db) y (cm) Z X,Y E-plane H-plane frequency (GHz) conventional thin substrate conventional thick substrate PBG substrate effective dielectric substrate x (cm) E (db) E db Pattern bifurcation!

17 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) x (cm) Z E-plane H-plane X,Y E db E (db) Thick Substrate (t=0.059λ 0, BW=4.3%) High Performance Radiation Pattern with improved Bandwidth No Pattern bifurcation!

18 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