Project Description
RF/Antenna Projects, EE Department,
Current EE department projects in the RF/Antenna area include:
- Development of HFSS computer models for metamaterial structures
- Development of physical metamaterial prototypes verified through measurements taken in the Cal Poly Anechoic Chamber
The development of HFSS simulation models for metamaterials has been established for split ring resonators (SRR) and capacitively loaded strips (CLS) as detailed in [1-3]. Both planar (Fig. 1)
Fig. 1: Unit Cell, Planar MetaMaterial HFSS Model and tri-planar models (Fig. 2) have been developed and simulation results compared.
Fig. 2: Unit Cell, Tri-Planar MetaMaterial HFSS Model
The planar model (Fig. 1) is composed of a box filled with 5880 Duroid (εr = 2.2) or FR4 with (x, y, z) dimensions of (0.210, 0.756, 0.156 inches). S-parameters are calculated as a function of frequency with the goal of |S11| → ∞ dB and |S21| → 0dB to yield a double negative material [Re(ε) < 0, Re(μ) < 0] response. Fig. 3 below illustrates the S-parameter response for the planar case (Fig. 1).
Fig. 3: S-Parameter Response, Planar MetaMaterial HFSS Model
This response indicates double negative properties (|S11| = -4dB and |S21| = -10dB) at the target frequency of 5GHz. To determine if the tri-planar structure yields an improvement in performance, the same measurement was performed: see Fig. 4 below.
Fig. 4: S-Parameter Response, Tri-Planar MetaMaterial HFSS Model
This response also indicates double negative properties (|S11| = -18.5dB and |S21| = -0.05dB), but at a frequency of 6.325GHz. Material dimensions can be scaled to obtain these characteristics at the target frequency (5GHz). Additional simulations are currently underway to characterize negative material characteristics with respect to unit cell geometries. To allow fabrication, simulation models align with materials (Roger’s Duroid and FR-4) available from substrate manufacturers. To detect negative index material characteristics, a prism structure of metamaterial unit cells [4] will be fabricated: see Fig. 5 below.
Fig. 5: Prism Geometry, MetaMaterial HFSS Model (left), Expected Ray Paths (right) [4].
Incident radiation will be applied at the x = 13cm plane at normal incidence (along the x-axis), while transmitted radiation will be measured as a function of angle (xy-plane) on both sides of the normal (at expected refracted angles) to verify negative index material performance. Applications of metamaterials include the focusing of light rays using rectangular (as opposed to convex) slabs of metameterial and the focusing of RF energy from small radiating apertures [3]: see Fig. 6 below.
Fig. 6: Application of Metamaterials: Focusing Radiation [5]
References
1. D.R. Smith, W. Padilla, D.C. Vier, S.C. Nemat-Nasser, S. Schultz, “Negative Permeability from Split Ring Resonator Arrays,” Lasers and Electro-Optics Europe, 2000, Conference Digest, 10-15 Sept 2000.
2. R.W. Ziolkowski, “Design, Fabrication, and Testing of Double Negative Matematerials,” IEEE Trans. Antennas Progat., Vol. 51, July 2003, pp. 1516-1529.
3. J.B. Pendry, A.J. Holden, D.J. Robbins, W.J. Stewart, “Magnetism from Conductors and Enhanced Nonlinear Phenomena,” IEEE Trans. Microwave Theory & Techniques, Vol. 47, No. 11, Nov 1999, pp. 2075-2084.
4. J.B. Pendry and D.R. Smith, “Reversing Light with Negative Refraction,” Phys. Today, 57, June 2004, pp. 37-43.
5. J.B. Pendry, “Negative Refraction Makes a Perfect Lens,” Phys. Rev. Lett., Vol. 85, No. 18, Oct 2000, pp. 3966-3060
Dean Arakaki
darakaki@calpoly.edu
