Focal plane arrays for large reflector antennas: first results of a demonstrator project

The surveying speed of large reflectors can be increased by one or two orders of magnitude when the focal fields are sampled with a dense phased array. In a dense array consisting of a large number of antenna elements (100 up to 1000), multiple beams can be synthesised and steered electronically. This collecting and manipulating of the entire electric field in the focal plane creates the possibility of a simultaneously improvement in the efficiency of existing telescopes and open up wide fields-of-view. This paper will describe the first results of the EU project FARADAY. The approach chosen in FARADAY is to use a Vivaldi array of 72 antenna elements configured in 8x9 grid. The analogue beamformer, integrated with the antenna array, syntheses beams by using for example 3x3 elements combined in three rings, where each ring is given a specific weight factor. The number of beams has been limited to two in this demonstrator project. Further more we will explore the possibilities and limitations of the large-scale use of Focal Plane Array's, in particular for the fourteen 25-meter reflectors of the Westerbork Syntheses Radio Telescope (WSRT).