Low side-lobe circularly-polarized phased arrays using a random sequential rotation technique

A novel technique is presented for sidelobe and axial ratio control of circularly-polarized phased array antennas. Although our new random sequential rotation (RSR) concept uses a regular periodic array grid, it provides similar properties as randomly-spaced array antennas. In this way, a wideband behavior is provided, without the appearance of grating lobes. In addition, the gain is maximized, since a uniform amplitude distribution is used. A 4 GHz prototype consisting of 16 aperturecoupled microstrip antennas with a beamformer was developed to demonstrate the basic properties of RSR array antennas. Although the element spacing is much larger than half a wavelength, well-controlled sidelobes are provided, even in the worst-case diagonal plane. The measured cross-polarization level at 4 GHz is below -20 dB at a 20-degree scan angle in the diagonal-plane.