Combline filters use coupled rods less than a quarter of a wavelength long shorted at the same end. Typically lengths between 30 and 55 degrees are used giving a compact, mechanically straightforward and versatile filter.
The unloaded Q of the capacitively loaded rods depends on how the capacitance is realised. Normally a tuning screw inside the resonator produces a resonably high Q. A lower frequencies or where short resonator lengths are required top hats or other folded features will be added to the end of the resonator. Resonators can be designed to be temperature stable by using combinations of metals and capacitive features.
The useful frequency rangy is 300MHz to 15Ghz
The combline structure is normally used for bandpass filters and diplexers.
Bandwidths 1% to 30%
Stopband Up to 5x CF depending on bandwidth and cavity size.
Connectors - Most types can be accommodated - PCB Mounted, SMA, N type, TNC, 7-16ths.