Band-pass filters are used to attenuate frequencies outside a narrow pass-band. They are commonly used as components in the design of combiners, for the attenuation of noisy side bands, to achieve additional decoupling between transmitters installed in close proximity in the same antenna system, and to combine digital channels with existing analogue channels.
The BF4-3CpppD band-pass filter consists of three magnetic coupled coaxial resonators with adjustable coupling and BF4-4CpppD with four and BF4-6CppD with six. One end of the resonator is open-circuited and the other short-circuited, and tuning is accomplished by rotating the circular central conductor at the lower end of each resonator. The coaxial input and output lines are coupled to the first and last resonator by magnetic coupling loops.
The band-pass filter is factory tuned to the desired operating channels. All filters are retunable on whole frequency bands IV and V.
All these filters are suitable to operate as an output filter of the transmitter, most commonly are used as components of combiners (starpoint or constant impedance combiners).
ELTI critical mask filters for DVB are all 6 cavity filters with elliptical response to satisfy critical mask requirements or adjacent channel configuration.
Main advantages of these filters are:
- foreshorten folded combline design,
- iris couplings with fine bandwidth regulation
- retunable on whole frequency bands IV and V.
Filters are part of ELTI complete solutions:
- transmitter TERX, as output filter available on request,
- regenerative repeater ARX, as output filter available on request,
- combiners for adjacent channel configuration and/or critical mask requirements.