A novel planar tunable bandstop filter based on simple coupled-line structure

A simple coupled-line structure is proposed to construct a novel planar bandstop filter. The reconfigurable performance is achieved by using tunable capacitors, namely, varactor diodes. The stopband of this filter can be tuned from 0.6 to 1.57 GHz when the capacitance of capacitors is in the range of 1 to 7 pF. Both simulated and measured results verify this proposed idea.