Frequency selective surface with repeating pattern of concentric closed conductor paths, and antenna having the surface
First Claim
1. A microwave frequency selective element being reflective in a first frequency band and transmissive in a second frequency band different from said first frequency band, comprising:
- a substantially periodic array of sets of radiators disposed along a surface of the element, wherein each of the sets of the radiators comprises at least two radiators of which one radiator is an innermost radiator and a second radiator is an outermost radiator which encircles the innermost radiator, each radiator having a configuration which encircles a point on the surface of the element;
wherein said second frequency band is lower than said first frequency band, and the outermost radiator has a circumference approximately equal to a wavelength of radiation in the lower one of said frequency bands.
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Accused Products
Abstract
A microwave element having a frequency selective surface (FSS) is formed of a substantially planar substrate of dielectric material which is transparent to electromagnetic radiation, and supports an array of radiators wherein the radiators are arranged in a plurality of sets of radiators. In each set of radiators, in a preferred embodiment, there are three concentric radiators fabricated of an electrically conductive material. The outermost radiator has a hexagonal closed form, and the inner radiators are configured as circular annuluses. In each set, the largest radiator has a circumference equal to a wavelength of a first frequency of radiation to be reflected from the (FSS), the sets being spaced apart by a spacing equal to one-third of the foregoing wavelength in the dielectric substrate. In a two-dimensional array of the sets of the radiators, the sets are located at vertices of equilateral triangles. An antenna incorporating the FSS includes a first horn operative at radiation of the foregoing wavelength and a reflector, both of which are disposed on one side of the FSS. Additional horns operative at higher frequencies located on the opposite side of the FSS for transmittal of radiation through the FSS.
110 Citations
17 Claims
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1. A microwave frequency selective element being reflective in a first frequency band and transmissive in a second frequency band different from said first frequency band, comprising:
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a substantially periodic array of sets of radiators disposed along a surface of the element, wherein each of the sets of the radiators comprises at least two radiators of which one radiator is an innermost radiator and a second radiator is an outermost radiator which encircles the innermost radiator, each radiator having a configuration which encircles a point on the surface of the element; wherein said second frequency band is lower than said first frequency band, and the outermost radiator has a circumference approximately equal to a wavelength of radiation in the lower one of said frequency bands. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An antenna comprising a reflector, a frequency selective element, and a plurality of microwave feeds positioned for illuminating said reflector wherein a first of said feeds operative at a higher frequency of radiation is located on a side of said frequency selective element opposite said reflector to permit illumination of said reflector by transmittal of radiation through said frequency selective element, and wherein a second of said feeds operative at a lower frequency of radiation and said reflector are positioned on a common side of said frequency selective element opposite said first feed for permitting illumination of said reflector by reflection of radiation at said lower frequency by said frequency selective element, and
wherein said frequency selective element comprises: -
a substantially periodic array of sets of radiators disposed along a surface of said element, wherein each of the sets of the radiators comprises at least two radiators of which one radiator is an innermost radiator and a second radiator is an outermost radiator which encircles the innermost radiator, each of said radiators having a configuration which encircles a point on the surface of said element; and wherein the outermost one of said radiators has a circumference approximately equal to a wavelength of the radiation at said lower frequency, said sets of radiators being spaced apart by a spacing equal approximately to one-half wavelength of the radiation at said lower frequency. - View Dependent Claims (16, 17)
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Specification