Electronically tunable microwave bandstop filter design and implementation

Oruç, Sacid
In modern broadband microwave applications, receivers are very sensitive to interference signals which can come from the system itself or from hostile emitters. Electronically tunable bandstop filters can be used to eliminate these interference signals with adaptation to changing frequency conditions. In this thesis, electronically tunable bandstop filter design techniques are investigated for microwave frequencies. The aim is to find filter topologies which allow narrowband bandstop or ‘notch’ filter designs with low-Q resonators and with tuning capability. Tunability will be provided by the use of electronically tunable capacitors, specifically varactor diodes. For this purpose, firstly direct bandstop filter techniques are investigated and their performances are analyzed. Then phase cancellation approach, which enables high quality bandstop filter design with lossy circuit elements, is introduced and analyzed. Lastly, a novel notch filter design technique called as all-pass filter approach is introduced. This approach allows a systematic design method and enables to design very good tunable notch filter characteristics with low-Q resonators. Three filter topologies using this approach are given and their performances are analyzed. Also prototype tunable notch filters operating in X-Band are designed and implemented by using these three topologies.


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Citation Formats
S. Oruç, “Electronically tunable microwave bandstop filter design and implementation,” M.S. - Master of Science, Middle East Technical University, 2010.