Alpes: a low profile electronically steered antenna for MobileSat(R) applications

An electronically steered phased array antenna for L-band mobile satellite communications applications using the Optus MobileSat(R) system is described. The antenna uses circularly polarised microstrip radiating elements in a conical arrangement with a profile only 120 mm in height including the radome. A closed loop tracking system based on the received RF signal strength and an open loop tracking system based on a gyroscope for beam steering during shadow conditions are incorporated within the antenna. The antenna has been designed and tested to operate in tough environmental conditions as encountered when mounted on road and track vehicles.