Low insertion phase variation dielectric material

Abstract

This invention is directed to an apparatus for transmitting an electromagnetic wave. The apparatus includes a dielectric material with a permittivity that decreases with increasing frequency over an operating frequency bandwidth that includes the frequency of the electromagnetic wave. With this behavior, the electrical or phase length of the dielectric material remains relatively constant and independent of frequency over the operating band, a feature that is highly advantageous for many important applications including circuit boards, radomes, and antennas. In addition, the dielectric material can be engineered to exhibit this behavior at a desired frequency, including frequencies in the millimeter, microwave, VHF and UHF frequency ranges. In a preferred embodiment, the dielectric material is an artificial dielectric manufactured by mixing conductive particulate into a host dielectric material. The conductive particulate can be microspheres or microfibers particularly with poor or medium conductivities, that have determined shapes and that are mixed in a volumetric proportion with the host dielectric material, to achieve the desired permittivity versus frequency behavior. With the microfibers, the maximum loss tangent occurs off the center frequency of the operating frequency bandwidth so that constant phase behavior can be obtained with relatively little wave transmission loss. The apparatus can also include a conductive material disposed in contact with the dielectric material, for transmitting the electromagnetic wave. The invention also includes related methods.