High resolution direction of arrival estimation methods applied to measurements from a digital array antenna

At the Defence Research Establishment of Sweden (FOA) an experimental S-band receiving digital array antenna for radar applications has been designed and built. It consists of a horizontal uniform linear array (ULA) of 12 antenna elements, whose digitized signals are processed in non-real time in a computer. Accurate calibration is utilized. We have compared several spectral and parametric direction-of-arrival (DOA) estimation methods for varying DOA separations, number of samples and signal-to-noise ratios (SNR) on measured data from an anechoic chamber. At ideal conditions the resolution can be improved considerably with model based DOA methods compared to conventional beamforming. We achieved a resolution below 1/10 of the resolution of conventional beamforming.