Performance of probe-fed microstrip-patch element phased arrays

The performance trends for large phased arrays with probe-fed microstrip-patch elements are discussed, with primary consideration given to single-probe (unbalanced) feed for rectangular grid arrays with rectangular patch geometry. The effects of substrate thickness and permittivity, patch dimensions, and element spacing are examined. Pronounced surface- and leaky-wave effects that tend to limit the scan volume are found. Interaction between the patch resonance at broadside scan and the leaky-wave resonances leads to an E-plane scan-bandwidth tradeoff. In the H-plane scan a transverse electric (TE)-type guided wave resonance is found that becomes pronounced when the H-plane dimension is a large fraction of the H-plane element spacing. This leads to a limitation of the H-plane patch dimension in the rectangular grid arrays. An element design procedure is proposed and illustrated for an element suitable for wide-angle scan over a ±5% frequency band