A Novel Approach to Mitigation of Radar Beam Weighting Effect on Coherent Radar Imaging Using VHF Atmospheric Radar

Multiple-receiver coherent radar imaging using very high frequency atmospheric radars is capable of imaging angular power distribution (termed brightness distribution) of the backscattered radar echoes with some inversion algorithms such as Capon´s method. The brightness distribution, however, is weighted by the radar beam weighting pattern. Modification of the brightness distribution with a simulated radar beam weighting pattern usually incurs spurious peaks around the edge of the distribution map. In view of this, an approach to mitigation of the radar beam weighting effect on brightness distribution is proposed, thereby giving more reliable estimates of echo center and brightness width. The proposed approach employs several pairs of symmetrically tilted radar beams to determine an effective weighting pattern of the radar beam that is adaptive to the signal-to-noise ratio (SNR) of the data, as well as the transmitting-receiving array configuration. Four radar experiments were carried out with the Middle and Upper atmosphere radar in Japan (34.85°N , 136.11°E) to demonstrate the proposed approach. One of the experiments was exhibited in more detail, and it showed the following: 1) Approximately 14% of the single-center cases turned into double-center situations; 2) the zenith angles of the corrected echo centers were larger than the original ones by ~0.75° on average; and 3) the brightness widths could be larger than the original ones by several degrees, depending on the SNR of the data. Based on these investigations, suitable corrections of the echo center and brightness width are expected to result in different estimates of some atmospheric parameters like scatterer anisotropy and tilt angle of the layer structure.