Resolution of coherent radar targets in the near field of an array antenna

In this paper we present the results of the research on radar target elevation estimation in the near field of the vertical line array antenna. In particular, we examine the case of targets at low elevations where coherent reflections from ground prevent accurate measurements of target angular positions. The estimation method used is a modified version of the MUSIC algorithm, adapted for the application in the near field antenna environment. A spatial smoothing preprocessing scheme has been applied in order to resolve close coherent signals. The algorithm has been successfully applied go both simulated and recorded radar data. Controlled Ku-band radar experiments were conducted at the Valley Forge Research Center of the University of Pennsylvania. Estimation of actual target elevations to within 1 standard beamwidth has been achieved for SNR´s of about 0 db.