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An antenna system includes an antenna element and an electromagnetic bandgap element proximate the antenna element wherein the electromagnetic bandgap element is optimized for narrow bandwidth operation thereby providing radiofrequency selectivity to the antenna system. Preferably the electromagneti

An antenna system includes an antenna element and an electromagnetic bandgap element proximate the antenna element wherein the electromagnetic bandgap element is optimized for narrow bandwidth operation thereby providing radiofrequency selectivity to the antenna system. Preferably the electromagnetic bandgap element is tunable such as through use of a bias-alterable dielectric substrate or other tuning mechanism. The design approach also provides a means of creating an ultra-thin low-profile narrowband tunable channel selective antenna system suitable for low frequency applications.

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What is claimed is: 1. An antenna system comprising: an antenna element; an electromagnetic bandgap element proximate the antenna element; wherein the electromagnetic bandgap element comprises a substrate with a metallic backing and a mosaic of conductive patches on a surface of the substrate optim

What is claimed is: 1. An antenna system comprising: an antenna element; an electromagnetic bandgap element proximate the antenna element; wherein the electromagnetic bandgap element comprises a substrate with a metallic backing and a mosaic of conductive patches on a surface of the substrate optimized for narrow bandwidth operation thereby providing radiofrequency selectivity; and a thin high-resistivity coating on the mosaic for allowing an even application of a bias voltage between the mosaic and the substrate. 2. The antenna system of claim 1 wherein the electromagnetic bandgap element is tunable. 3. The antenna system of claim 2 wherein the electromagnetic bandgap element comprises a dielectric substrate with a bias-alterable dielectric constant. 4. The antenna system of claim 3 wherein the dielectric substrate has a dielectric constant of more than about 40. 5. The antenna system of claim 3 wherein the dielectric substrate has a dielectric constant of more than about 85. 6. The antenna system of claim 1 wherein the antenna system has an operation frequency of less than about 1 GHz. 7. The antenna system of claim 1 wherein the electromagnetic bandgap element is optimized for narrow bandwidth operation by use of a suitable cell geometry. 8. The antenna system of claim 1 wherein the electromagnetic bandgap element is of an artificial magnetic conducting (AMC) surface type. 9. The antenna system of claim 1 wherein the mosaic is patterned to provide for narrow bandwidth operation. 10. The antenna system of claim 9 wherein a genetic algorithm is used in patterning the mosaic to provide for narrow bandwidth operation. 11. The antenna system of claim 1 wherein an overall thickness of the electromagnetic bandgap element is less than about λ/100 wherein λ is a wavelength of the antenna system. 12. The antenna system of claim 11 wherein the antenna system has an operating frequency (c/λ) of less than about 1 GigaHertz. 13. The antenna system of claim 1 wherein an overall thickness of the electromagnetic bandgap element is less than about λ/1000 wherein λ is a wavelength of the antenna system. 14. The antenna system of claim 1 wherein an overall thickness of the electromagnetic bandgap element is less than about λ/2000 wherein λ is a wavelength of the antenna system. 15. The antenna system of claim 1 wherein the narrow bandwidth is less than about 5 percent of a center frequency of the antenna system. 16. The antenna system of claim 1 wherein the narrow bandwidth is less than about 1 percent of a center frequency of the antenna system. 17. The antenna system of claim 1 wherein the narrow bandwidth is less than about 0.1 percent of a center frequency of the antenna system. 18. An artificial magnetic conducting (AMC) surface for use in an antenna system to provide a narrow bandwidth of operation and radio frequency selectivity, comprising: a substrate of a dielectric material; the substrate patterned with conductive patches to provide a unit cell geometry; wherein the unit cell geometry is optimized for narrow bandwidth operation thereby providing radiofrequency selectivity; and a thin high-resistivity coating on the substrate patterned with conductive patches to allow application of a uniform bias voltage between the conductive patches and the substrate. 19. The AMC surface of claim 18 wherein the substrate is tunable. 20. The AMC surface of claim 18 wherein the narrow bandwidth of operation is less than about 5 percent of the operating frequency. 21. The AMC surface of claim 18 wherein the narrow bandwidth of operation is less than about 1 percent of the operating frequency. 22. The AMC surface of claim 18 wherein the narrow bandwidth of operation is less than about 0.1 percent of the operating frequency. 23. The AMC surface of claim 18 wherein the substrate has a dielectric constant of at least about 40. 24. The AMC surface of claim 18 wherein the substrate has a dielectric constant of at least about 85. 25. The AMC surface of claim 18 wherein the substrate has a thickness of less than about λ/100, wherein the operating frequency given by c/λ, is less than about 1 GHz. 26. The AMC surface of claim 18 wherein the substrate has a thickness of less than about λ/1000, wherein the operating frequency given by c/λ, is less than about 1 GHz. 27. An antenna system comprising: an antenna element; an electromagnetic bandgap element proximate the antenna element; the electromagnetic bandgap element comprising a substrate of a dielectric material patterned with conductive patches overlaid with a thin high-resistive coating to provide a unit cell geometry suitable for narrow bandwidth operation of less than about 5 percent of an operating frequency to thereby provide radiofrequency selectivity; the operating frequency less than about 1 GHz. 28. The antenna system of claim 27 wherein the electromagnetic bandgap element is tunable.