A Hybrid Divider uses a hybrid transformer core with a few windings and a 2R termination resistor between ports 2&3 so that coupling between the two outputs cancels out when all ports are terminated with R.
The same is used in Cable TV biz is called a splitter. It is bidirectional but 75 Ohms not 50. 30 dB isolation is normal when the feed point is terminated with proper impedance, otherwise it is 0dB. Since this is bidirectional and broadband you can use them as combiners 2 to 1 port or as splitters 1 to 2 ports. If one port out is a small sample, they are often called by their generic name " Directional Coupler." and labelled by the theoretic sample size such as -20dB is a DC20.
There are also crystal versions of splitters with frequency selective characteristics in research papers.
Ideally all DC-3's are -3dB out in theory but in practise 3.5dB is the best you can achieve ( unless you are a guru of Directional Coupler design then you can get -3.4dB , whom I once met and he told me how many microwave repeaters ) 0.1dB saved across Canada in the 70's) He was also a small potato farmer in Quebec.
So remember a Hybrid Divider, power divider, signal divider, combiner , splitter and Dirctional Couple with 3dB in theory are all names for the similar products with slightly different variations in application, but a Hybrid implies a certain balanced splitter transformer design vs a WIlkinson design or circulator design or passive R divider design. etc.
IN your 2nd topic on BPF, the Bandstop rejection will be dependant on the actual part number of which there are hundreds but in general proportional to the cost and number of Poles or cascaded stages of dielectric resonators, in this case all tuned for some shape such as Chebyshev, Elliptical, Cauer, etc, for tradeoffs between passband ripple and skirt steepness and bandstop minimum rejection.
e.g. **broken link removed** Since they are custom, large orders and customer & factory specs are usually negotiated. But work very well.
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