A new method to improve the rejectband of a 5.6 GHz bandstop filter using λ/2 open-loop ring microstrip resonators

In this paper, a new compact bandstop microstrip filter using two cascaded ring resonators has been designed, fabricated and measured. The lambda/2 open-loop-ring resonators are used to obtain the sharp cut-off frequency response as well as a good filter performance in both the pass-band and the stop-band. The equivalent circuit model has been developed to characterize the proposed bandstop structure. The both equivalent circuit and the electromagnetic simulations are in a good agreement with the measured results.