Generation and properties of synthetic aperture polar diagrams for use in DF systems

A synthetic aperture method of generating polar diagrams with shapes which conform to Bessel functions rather than the more familiar sin x/x form is described. The method can be used to generate, using a circular array, polar diagrams for use in Doppler DF and VOR beacon systems. This generation avoids the amplitude limiting employed in conventional forms of these systems. The method is applicable to linear arrays and can be used in microwave landing aids. In this application, a very good side lobe performance superior to the (sin x)/x form is obtainable. The site error suppression performance of a Doppler DF having a synthetic aperture is compared with a conventional Doppler system. Both are compared with a standard based on utilisation of a (sin x)/x lobe structure. No practical work on a DF system has been undertaken, although the generation has been used in another project; some measured results are given in this respect. The main conclusion is that the generation will enable the Doppler DF concept to eliminate the disadvantage of being prone to considerable inaccuracies, as caused by abnormally strong reflections