C-Band Iris Coupled Cavity Bandpass Filter

This paper presents the design of compact, tunable, high rejection 6th-order C-Band Iris Coupled Cavity Bandpass Filter. The design approach followed includes the use of Chebychev low pass filter prototype elements to calculate normalized capacitance per unit length between resonators & ground and also between adjacent resonators. With the help of coupling and tuning screws, the bandwidth and center frequency of the filter can be tuned for desired performance. Coaxial capacitance formula is used to compute the diameter of the screws. CST tool is used to simulate & optimize the theoretically calculate physical dimensions to further improve the filter performance and obtain better tolerance sensitivity. Finally, a 6th order prototype is fabricated and tuned to obtain the desired performance. The cavity design & resonator calculations have been carried out in such a manner that the same hardware can be tuned to both the frequency bands i.e., 4.4-4.6 GHz (Band I) and 4.8-5.0 GHz (Band II) to meet the desired specifications. A prototype is fabricated and experimental validation is presented.