A bandstop filter with reconfigurable two-state center frequency and bandwidth is presented. The prototype of the proposed reconfigurable bandstop filter consists of one section of anti-coupled line short-circuited by an open low-impedance line. By introducing PIN diodes, this bandstop filter exhibits a lower stopband response centered at a lower frequency in the ON state, and a wider stopband response centered at a higher frequency in the OFF state. Filter using the proposed structure is designed, simulated and measured. The results confirm the designing method by showing a narrow stopband with the center frequency of 1 GHz and a wide stopband of 2.9 GHz bandwidth centered at 2.5 GHz respectively.
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