Harrington's Formula Extended to Determine Accurate Feed Reactance of Probe-Fed Microstrip Patches

A simple formulation is presented as an extension of Harrington's formula to accurately estimate the feed reactance of probe-fed microstrip patches. This, unlike previous formulas, can efficiently address all sorts of variations of microstrip and probe parameters resulting in a more versatile form. Computed results are verified with some representative measured data on rectangular and circular microstrips, thus, providing confidence in the new formula and its accuracy