N121-086 TITLE: Large-scale Electromagnetic Metamaterials for Shipboard Applications

TECHNOLOGY AREAS: Ground/Sea Vehicles

ACQUISITION PROGRAM: PEO Ships, Integrated Topside INP

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OBJECTIVE: Establish approaches and develop techniques to design and manufacture low-cost, large-scale artificially structured metamaterials operating in the radio frequency (RF)/microwave band.

DESCRIPTION: An electromagnetic (EM) metamaterial is an engineered composite material that reacts to incident EM radiation with a response that cannot be found in conventional materials. Electromagnetic metamaterials are often constructed of periodic arrays of conducting resonators (e.g., split-ring resonators and/or wires) which respond to the applied field to produce the electromagnetic properties beyond what is found in nature. The structural arrangement of the resonating elements gives the desired electromagnetic properties. Ideally, the matrix in which the resonators are embedded would have permittivity and permeability close to free-space and low loss at the frequencies of interest, to minimize reflection and absorption.

Recent scientific and technical advances in the field of EM metamaterials have demonstrated materials with simultaneously negative effective permittivity and negative magnetic permeability, yielding a negative refractive index. This opens up entirely new possibilities for the manipulation of electromagnetic waves over a very broad spectrum from the visible, through the infrared (IR), to the microwave. One major barrier to employing this technology in the Navy fleet is the need for low cost, low loss, large volume fabrication technology. Thus there is a need to research and develop techniques to manufacture these metamaterials on a cost and size scale relevant to defense applications for ground and sea vehicles. The interplay between the specific design of the metamaterial and the fabrication concept will need to be investigated as part of the approach.

PHASE I: Develop innovative concepts for low-cost, high-volume fabrication of artificially structured EM metamaterial for use in composite structures with linear dimensions on the order of 1 meter. Identify materials and methods of fabrication that would lead to a robust structure capable of meeting design requirements of permittivity and permeability for practical applications. Propose a demonstration metamaterial application of interest to the Navy, which will incorporate the innovative fabrication concept and would require meter scale metamaterial composites.

Critical aspects would be designs that are lightweight, low loss, broadband, and at the lowest possible cost. Tolerances of the typical unit cell patterns produced must equal or exceed those of standard printed circuit board technology, which are approximately 1 mil (25um). Thermal stability of the substrates used should not exceed a ~2% change in linear dimensions over the range -65oC to 185oC. The substrate dielectric materials should have dielectric uniformity tolerance of <2 %. Layer-to-layer registration of metamaterial layers should have a tolerance of less than 5% of the unit cell linear dimensions. The resulting metamaterial composite must be compatible with naval fire safety and structural requirements for shipboard applications.

PHASE II: Build a prototype of the necessary tooling and demonstrate the fabrication concept developed in Phase I. Use the innovative fabrication technique to demonstrate a meter scale prototype metamaterial topside application functional in the microwave band. The metamaterial composite prototype will be tested against proposed electromagnetic and structural performance criteria.

PHASE III: The small business will work with the Navy and industry to transition metamaterials to relevant shipboard and military environments. Low cost, low loss, large scale electromagnetic metamaterials fabrication is an enabling technology with potential applications in a number of integrated topside design systems. For example, antenna isolation surfaces, low observable antennas, frequency selective surfaces, radar absorbing materials, compact waveguides, beam forming lenses, and impedance matched radomes.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Electromagnetic metamaterials with tailored permittivity and permeability have many uses where one wants to control or direct the propagation of radiation. A useful application is for antenna isolation surfaces for clusters of antennas and structures where interference is likely, such as cell-phone base stations and cluttered commercial communication systems. Lightweight beam forming lenses for communications satellites is another potential commercial application.

REFERENCES:
1. R. A. Shelby et al. Science, 292, p 77 (2001).

2. J.B. Pendry and D. R. Smith, Physics Today, 57, p. 37 (2004).

3. A. F. Starr et al., Phys. Rev. B 70, 113102 (2004).

KEYWORDS: Metamaterials; Microwave; Electromagnetic; Magnetic Permeability; Electric Permittivity

** TOPIC AUTHOR (TPOC) **

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