Electronically Tunable Microwave Bandstop Filters

The design procedures for varactor tuned bandstop filters are presented. A novel circuit technique for realizing bandstop filters with a symmetrical frequency response is described and explicit design formulas are presented. The physical design and experimental performance of a three cavity varactor tuned bandstop filter tunable around 4 GHz is presented. Experimental results are substantiated with computer analysis which includes the effects of varactor resistance.