Polarisation Dependent Scattering from the Serrations of Compact Ranges

Serrations are often applied at the edges of compact range reflectors in order to reduce the scattering from the edges into the quiet zone. At low frequencies the serrations show different scattering of the field at the two polarisations: parallel to and perpendicular to the serration teeth.

This has been verified by modelling a range by the Method of Moments (MoM). The size of the range reflectors is about 7.5 m by 10 m which make the reflectors difficult to handle by MoM even at a frequency which is low for the range, viz. 1.7 GHz, in which case the reflectors are each 2400 wavelengths squared.

A narrow strip, horizontal or vertical, across the reflector and closed by a single serration tooth at each end is shown to give a good prediction of the field along a line parallel to the strip in the quiet zone. By this simple model of the range it has been demonstrated that the quiet-zone field depends highly on the polarisation. When the polarisation is parallel to the teeth the quiet-zone field has ripples which are 0.3 dB peak-to-peak, but for the perpendicular polarisation the field variations are 0.8 dB peak-to-peak.

The results are compared to quiet-zone fields determined by Physical Optics (PO).

Publication: AMTA 29th Annual Symposium (AMTA2007)
Place: St. Louis, MO, USA, 4-9 November, 2007