  This report was submitted as part of the SKA Low Frequency Aperture Array
Critical Design Review describing the design of the SKA1-LOW station that took
place between 2013 and 2018.
  The SKA1 LOW field station is inscribed in a circular area having an
effective station diameter (centre to centre) of 38 meters and has 256 SKALA4
elements. This document describes the electromagnetic design of the field
station. In particular it describes the layout design and the electromagnetic
modelling and characteristics of the station. This document describes the
effects associated with the layout and array such as mutual coupling effects,
side lobe pattern and beam shape (eg. smoothness, calibration models) and
presents the state of the art of our ability to measure the array performance
and validate the simulation work. The current LFAA field node requirements,
derived from the SKA L1 requirements, have evolved over the last years since
the LFAA PDR and the System Baseline Design. The SKA1 LOW field station has
been designed to meet those requirements and has therefore tracked their
evolution (eg. sensitivity requirements, array diameter, etc.). The
aforementioned requirements represent a very tight space with a desire for very
high sensitivity over a large frequency range (7 to 1) and wide field of view
(90 degrees cone around zenith) while keeping the station diameter to a
minimum, so as the filling factor but at the same time allowing for sufficient
space between antennas to allow for easy maintenances, amongst many others.
This results in a complex design.
