Active varactor tunable microwave filters

This paper presents measured results for active microwave bandstop and bandpass varactor tuned filters. These filter designs were based on the negative resistance method and were realised using microstrip with future MMIC implementation in mind. Tuning ranges of 0.3 and 0.6 octaves around a centre frequency of 1.8GHz were achieved. A significant improvement in filter performance was observed with results approaching those for lossless filters.

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