Broadband-configurable bandstop-filter design employing a composite tuning mechanism

A microwave bandstop-filter design is reported, which combines both continuous and discrete tuning using varactor and PIN diodes to achieve a two-octave tuning range. The useable passband for any given tuning point is limited, however, the composite tuning mechanism in the topology facilitates the separate tuning of the centre frequency and stopband to minimum-loss passband separation. A suitable and novel filter-synthesis procedure is developed, and the filter performance is verified through experimental results