Axial ratio measurements for various DFSAR modes of operation. Top: The bar chart on the left illustrates the ellipticity of the transmitted signals (for the L-band SAR, shown as an example) corresponding to different phase-shifter settings, and the inset table on the right shows axial ratio measurement results for L- and S-band transmission modes. The minimum axial ratio of 0.39 dB corresponds to phase-shifter settings of 45° and 0° of H and V transmit chains, respectively, summarily represented as H45V0 on the x-axis. Bottom: The sense of circularly polarized signals (LHCP/RHCP) is cross-verified using helical antennas of the corresponding polarization. The ellipses at the bottom of the figure represent the variation of the transmit signal amplitude radiated by the SAR antenna and measured using a linearly polarized probe at different orientation angles as specified in the plots.