A high performance spider subarray of five microstrip patches

A microstrip subarray including a central patch surrounded by four or six other patches can provide low sidelobes in the radiation pattern, since a significant portion of radiation comes from its center. This is more difficult to achieve without a central patch, since it would have an aperture field distributed mainly on its corners. However, such an arrangement gives an odd number of radiators, and therefore leads to a design problem for the corporate feed. This can be overcome by feeding the central patch, and by using microstrip line sections to propagate a resonant standing wave to feed the surrounding patches. This results in a simple feeding network, realized by four halfwave line sections. No power divider is necessary, but a careful optimization of this array is required. The resonance of the patches and that of the feeding lines can indeed be adjusted so that their juxtaposition widens the bandwidth, and maintain a high polarization purity in the field distribution.<>