Radiation characteristics of a broadband tapered slot antenna array demonstrator

The design and evaluation of properties of a 6-18 GHz dual polarised array antenna is reported. The antenna consists of two co-located linear polarised arrays, with 7x8 tapered slot elements each. The main focus is on experimental evaluation of the radiation characteristics of the antenna. The work has been carried out as part of the Electronic Warfare research program at FOI The measurements show that a small array can have radiation properties that are in good agreement with ideal, theoretical radiation patterns, in a broad frequency range and for steering angles up to 60 degrees. Interior elements exhibit better agreement than edge elements, as expected. The best agreement is found in the E-plane with more significant discrepancies at low frequencies in the H-plane. This is thought to be due to edge effects, because of the rather small size of the array in terms of wavelength. Experimental and theoretical investigations further predict that the radiated field from an element vanes with scan angle, from linear polarisation in the principal E- and H-planes to elliptical polarisation in the diagonal planes. Theoretical simulations further predict that the phase centre is different in the E- and H-planes of an element. The frequency dependence of the polarisation is small in the principal planes and, more pronounced in the D-planes.