Antenna Pattern Analysis and Measurements for Multiparameter Radars

Abstract

Measuring the full polarization matrix using a research radar requires knowledge of the complex (i.e., amplitude and phase) antenna pattern to properly correct for bias errors in the measurements. However, generally only power patterns are available for analysis. Techniques are presented for obtaining bounds on the system differential reflectivity ZDR bias and the integrated cross-polarization ratio. A method for use of the phase shift between pulses to simultaneously estimate the differential phase and the radial velocity over the full Nyquist interval is described. NCAR's CP-2 10-cm antenna patterns with different horizontal and vertical polarization sidelobes were matched by rotating the feed support struts to be aligned on the diagonals so no preferential blockage occurred. The matched antenna patterns show much improved ZDR measurements in strong reflectivity gradients. The CP-2 3-cm antenna patterns were shown to be axially symmetric and typical of a well-designed, unblocked parabolic reflector.