A Comparison of Techniques for Achieving Fine Azimuth Resolution

In the discussion of techniques for achieving azimuth resolution, it is instructive to compare the achievable resolution for three cases: 1) the conventional case for which ¿R Res = k ¿ D 2) the unfocussed synthetic antenna case for which Res = k¿¿R 3) the focussed synthetic antenna case for which Res = kD where ¿ is wavelength, D is aperture of physical antenna used, and R is range, and the k´s are constants of proportionality. These cases are compared. It is shown for unfocussed synthetic antennas that there is a maximum length which depends on range and wavelength. This restriction on length can be removed by focussing. A number of degrees of freedom exist for the design of a synthetic antenna which are not available for a real linear array. Among these is the ability to focus simultaneously at all ranges.