Explicit efficient coupling impedance formulas for the right-angled isosceles triangle and application to a circularly polarised truncated corners square patch antenna

Formulas for the four possible microstrip coupling impedances between two perimeter ports on a right-angled isosceles triangular microstrip segment are derived by integration of the associated Green´s function. The formulas are economised by introducing closed forms of infinite series to give new efficient computational formulas, which are verified experimentally. The variation of input impedance with offset, for a circularly polarised truncated corners square patch antenna, is determined using the segmentation method. Predicted and simulated results shows very good agreement. The area of the perturbation segments increases as a function of offset and this increase reduces the effect of manufacturing errors. A simple matching network for the offset feed is designed for an antenna operating at 2.45 GHz. Predicted, simulated and practical results show good agreement.