Analysis of an ultra wideband aperture array element for low frequency radio astronomy

This analytical study of an ultra wide band bow-tie element in an infinite regular array environment tries to give designers some useful hints on how to face a preliminary design of a radio astronomy instrument based on aperture arrays in terms of the effective aperture of the unit cell.

Introduction

The next generation of radio telescopes currently being designed will use so-called aperture arrays [1] as the core collector technology. These are phased arrays composed of several thousand antenna elements which are used to directly sample the incoming wavefront. The Square Kilometre Array (SKA) is the focus of this development work. This instrument will provide about two orders of magnitude improvement in sensitivity over existing facilities, but many thousand times improvement in the speed with which the sky can be imaged. This performance is required to deliver the scientific objectives of the experiment [2]. One part of the SKA design (SKA AAlo) calls for an ultra wideband antenna array able to operate from 70 to 450MHz. There are clear cost savings if this frequency range can be covered by a single antenna technology.