ANALYSIS OF A CYLINDRICAL-RECTANGULAR MICROSTRIP STRUCTURE WITH AN AIRGAP

The resonance problem of the cylindrical-rectangular microstrip struct ure with an airgap between the substrate layer and the ground conducti ng cylinder is studied by using a rigorous full-wave approach and a mo ment method calculation. The resonance condition is satisfied by compl ex resonant frequencies, which provide the information of resonant fre quency and half-power bandwidth of the structure. Numerical results in dicate that, with the increasing of the airgap thickness, the half-pow er bandwidth of the structure at the efficient radiating mode of HE01 is considerably increased, which improves the narrow bandwidth charact eristics of microstrip structures. Details of the numerical results, i ncluding the results for the planar rectangular microstrip structure w ith an airgap, are presented and analyzed.