FEEDS FOR DUAL-REFLECTOR ANTENNA SYSTEMS

Cassegrain and Gregorian feeds are universally used in dual-reflector antenna systems to achieve high efficiency, low antenna noise temperature and good cross-polarization. For aperture sizes greater than 100 wavelengths, shaped designs are available to achieve 65 - 75% aperture efficiency.
Seavey Engineering produces all types of Cassegrain and Gregorian feeds, including:

• Ring arrays to add lower-frequency capability to existing antennas

Monopod feeds incorporate into one integrated assembly the feedhorn, all RF feed chain components, the feed support tower and the subreflector with its ogive-shaped riser/feed cover. Monopod feeds are pre-aligned and mount to the vertex of the reflector. Shaped designs in this style are available.

Dual-band feeds utilize corrugated conical horns for the lower frequency and a special polyrod radiator for the higher frequency. Special OMTs have been developed which permit the higher-frequency circular waveguide to exit the rear of the assembly. Various polarization options are possible with this technique. The phase centers of each feed are coincident. Other options include redundancy switching, BIT injection ports and remote polarization rotation.

Ring feed systems are arrays of radiating elements placed around the periphery of existing Cassegrain feeds.They do not block the feed aperture. They clip onto the feed window flange and can be added without disrupting the central horn’s function. They add lower-frequency capability to existing antennas. Standard designs are available in L- and S-bands.

For large Earth Stations used in INTELSAT applications, feed systems include the feedhorn and window, 2- or 4-port OMT, feed tower, a composite, precision shaped subreflector and main reflector shaping coordinates.

For these systems, complete test reports are provided of the electrical performance of the entire antenna system.

"MONOPOD" CASSEGRAIN

Model 8729-800. 4-Foot Portable Ku-Band Cassegrain Antenna. This highly portable VSAT system uses a removable monopod-style Cassegrain feed with a conical corrugated horn and a selection of OMTs and filters. A VSAT radio operating in the 11.7 - 12.2 and 14.0 - 14.5 GHz bands is provided. The entire antenna breaks down for transport and includes a rugged tripod mount.

Model 9012-800. Ku-Band Monopod Feed System for a 3.5M Reflector.Standard Cassegrain. The feed includes a selection of 2-port and 3-port OMTs and filters. It operates in the 10.95 - 12.2 and 14.0 - 14.5 GHz bands. Polarization can be rotated remotely.

Model 9257-801. X-Band Monopod Feed System for a 2.4M Reflector. Standard Cassegrain. The feed is a corrugated horn equipped with a hybrid circular polarizer. Bandpass filters are included in the feed chain. It operates in the 7.25 - 7.75 and 7.9 - 8.4 GHz bands. This feed system is also available as Model 9763-800 for a 3.0M reflector.

Model 8729-800 4-foot Ku-band Monopod

Model 9012-800 3.5M Ku-band Monopod Feed (less support and subreflector)

Model 9257-801 2.4M X-band Monopod