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A DUAL MODE K-BAND ANTENNA

IP.com Disclosure Number: IPCOM000007163D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2002-Feb-28
Document File: 3 page(s) / 125K

Publishing Venue

Motorola

Related People

R. G. Foncannon: AUTHOR

Abstract

This publication describes a dual mode K-Band antenna for use on spacecraft communications links. A constellation of Low Earth Orbit (LEO) satel- lites is being developed for the Iridium7M'SM program which uses communication links between satellites (SV) and Earth stations in the 30/20 GHz commu- nications band. Each SV contains four high data rate K-Band links using gimbaled spot beam anten- nas and one omnidirectional low data rate link. Due to the small size ofthe SV nadir pointing panel, it is difficult to obtain a clear 180" field of view for the omni antennas without interfering with the movea- ble spot beam antennas. Antenna towers are required for the omni antennas to raise them above the spot beam antennas to give the required field of view. For certain combinations of spot beam azimuth and elevation angles, the spot beam antennas point directly at the omni antennas, causing degradat,ion ofboth the omni and spot beam patterns.

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MOTOROLA Technical Developments Volume 21 February 1994

A DUAL MODE K-BAND ANTENNA

by R. G. Foncannon

This publication describes a dual mode K-Band antenna for use on spacecraft communications links.

  A constellation of Low Earth Orbit (LEO) satel- lites is being developed for the Iridium7M'SM program which uses communication links between satellites (SV) and Earth stations in the 30/20 GHz commu- nications band. Each SV contains four high data rate K-Band links using gimbaled spot beam anten- nas and one omnidirectional low data rate link. Due to the small size ofthe SV nadir pointing panel, it is difficult to obtain a clear 180" field of view for the omni antennas without interfering with the movea- ble spot beam antennas. Antenna towers are required for the omni antennas to raise them above the spot beam antennas to give the required field of view. For certain combinations of spot beam azimuth and elevation angles, the spot beam antennas point directly at the omni antennas, causing degradat,ion ofboth the omni and spot beam patterns.

  Referring to Figure 1, Spot beam antenna 3 is rotated 360" by Azimuth gimbal 4 and +/-63" by Elevation Gimbal 7. The entire antenna assembly is mounted on the nadir pointing panel of the IridiumTM'SM SV along with three other spot beam antennas (less the omni antennas 1, 2 as shown). Receive omni antenna 1 and transmit omni antenna 2 are mounted on elevation yoke 6. As elevation yoke 6 moves spot beam antenna 3 in azimuth, omni antennas 1 and 2 move with it. When spot beam 3 is moved in elevation by elevation gimbal 7, spot beams 1,2 are not at?ected. Instead of omni antennas 1, 2 being fixed in one location where spot beam antenna 3 could point directly at for a low elevation angles and certain azimuth directions, the spot beam antennas 1, 2 always rotate out of the way of the

main spot beam. This eliminates any interference between the spot beam antenna 3 and the receive and transmit omni antennas 1,2.

  Referring to Figure 2, in the IrridiumTM'SM sys- tem the center spot beam antenna 3 and the omni antennas 1, 2 share the same K-Band Transmit/ Receive electronics 10. The dual mode K-Band antenna switches be...