Correction to Improved formulas for input impedance of coax-fed microstrip patch antennas

In a recently published article by E. Lier [1] an approximation to the radiation conductance of a circular microstrip antenna was given. The presented formula was a three term Taylor expansion in inverse power of er. Unfortunately, the presented formula was incorrect in the last term. Because such a formula is useful for rapid calculations, the formula is corrected and a five term formula is presented here.