Dual-band offset Cassegrain sub-reflector and antenna using the same

Dual-band Cassegrain sub-reflector based on an octagonal metal ring frequency selective surface

This technology features a frequency selective surface unit cell with a symmetrically stacked structure of dielectric, metal ring, and surface layers on both sides of a middle layer, with embedded dual metal rings. By periodically arranging these cells, the technology creates an offset Cassegrain sub-reflector and antenna that transmits one frequency band while reflecting another.

Handling two different frequency bands with a single reflector antenna previously required adding extra reflectors or increasing the antenna size. Approaches that applied frequency selectivity directly to the main reflector faced limitations due to significantly increased computational time and implementation costs.

This technology applies frequency selectivity to a hyperbolic sub-reflector instead of the main reflector, designed to transmit the 10–28 GHz band and reflect the 30–50 GHz band. Since side and bottom feed units handle each band separately, dual-band operation is possible without increasing physical size. It can be applied to satellite communication ground stations and Ku/Ka-band radar antennas, allowing both bands to be operated simultaneously with a single reflector structure.

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Key Features:

• Symmetrical multilayer structure consisting of first and second dielectric layers, metal ring layers, and surface layers stacked on each side of a middle layer
• Dual metal ring structure including an outer metal ring and an inner metal ring, with the rings embedded in the metal ring layer to contact the surface layer
• Metal ring dimensions limited to an outer ring side length of 0.06–0.08 cm, an inner ring side length of 0.03–0.04 cm, and a width of 0.02–0.03 cm
• Dual-band antenna where the sub-reflector at the main reflector's focal point reflects first-band signals to a side feed and transmits second-band signals to a bottom feed

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