Reconfigurable matched bandstop filter

This paper demonstrates a reconfigurable matched bandstop filter. The filter is based on a lossy allpass network. The lossy allpass network demonstrates the concept and design of perfectly matched bandstop response with a perfect matched at all frequencies. The filter is based on the half-wavelength λ over 2 resonator with gap coupling, parallel with an allpass nominally-90°-phase-shift element, which can be optimized to achieve high Q-factor. The reconfigurable matched bandstop filter can be realized by using PIN diodes as a switching element. This filter provides two state of operation under two conditions. The first condition is that the filter will produce allpass response when the PIN diodes are turned `ON´. The second condition is that the filter will produce bandstop response when the PIN diodes are turned `OFF´. Theoretical analysis together with experimental results is presented in this paper.