Capacitive-iris-type mechanically tunable waveguide filters for the X-band

Waveguide filters using capacitive obstacles appear essentially more suitable than those using inductive obstacles for applications involving tuning over a wide frequency range. Q-factors of waveguide filters with inductive and capacitive obstacles and a central tuning screw have been derived showing the comparison between the two types of filter when tuned over 500 Mc/s in the X-band. The paper describes two possible solutions leading to multi-cavity filters tunable over several hundred megacycles per second in the 8.5–9.5 Gc/s range, and adjustable to give a wide range of bandwidths and performances.