A comparison of the performance of reflector and phased-array antennas under error conditions

The successful deployment and operation of space-based radars (SBR) for the surveillance of near-earth military targets depends on the sound choice, design, and manufacture of large, space-deployable antennas. The performance in terms of axial gain and sidelobe level of two types of antennas under mechanical error conditions is examined and compared: a symmetric paraboloidal reflector with a large f/D ratio, and a rectangular phased-array antenna of the same directivity. The mechanical errors considered in the analysis for the reflector are its surface errors and, for the phased array, its element position errors. The analysis indicates the relative robustness and tolerance limit required for the two types of antennas. A comparison from the point of view of the highest sidelobe (i.e. the first minor lobe) under error conditions indicates that the reflector is far less favorable than the phased array.<>