Modal-expansion analysis of electrically steerable passive array radiators (ESPAR)

The modal-expansion method has been used for analyzing electrically steerable passive array radiators (ESPAR) driven by a gap source. A simple model of a four-element ESPAR antenna has been studied and its S-parameter results are in good agreement with those by HFSS. A designed seven-monopole ESPAR antenna has been discussed and simulation results have shown that it can be used to steer its radiation beam by properly adjusting the loaded varactors of its passive elements.