Stacked square ring resonators for bandwidth enhancment

The advantages of microstrip structures as antenna elements or resonators have aroused much interest in their theoretical and experimental studies. A novel structure that has not been studied well yet is the square ring patch, which is geomechanically an intermediate configuration between a printed loop and a patch. Several interesting features are associated with this patch. Its size is substantially smaller than that of a conventional square patch, and it depends on the ring width. Also, its input impedance is considerably higher, whereas its impedance bandwidth is smaller, in comparison with a similar size patch. Normally, the deviation of its properties from those of a square patch increases by decreasing its width. It is known that stacking similar size patches increases the impedance bandwidth. We investigate this property for two stacked square rings. A number of simulations are carried out, using "Ensemble 4.02 of Boulder Microwave Technologies Inc." to understand the behaviour of stacked rings, and determine suitable parameters. An optimized configuration is also fabricated and tested.