We have a product that is a shelf with a backplane into
which plugs 2 power supplies and 8 modules. The 8 modules
are all in parallel to one another and are capable of
talking to one another through the backplane.  A single
module contains 2 boards that are each 50 ohm boards.
These two board are also in parallel with each other.

16 connectors in the backplane for 16 PCBs each
50 ohms. For any type of configuration, a single
50 ohm board is capable of talking to as many as
2*N + 1  other 50 ohm boards where N = # modules in shelf
and  1 = the other board in its own engine.

In other words,
# modules in shelf      # of other 50 ohm boards one board
                                  talks to through the backplane
                          dependent upon configuration of
                          shelf.

1 module                         1 other 50 ohm board
2 modules                        3 other 50 ohm boards
3 modules                        5 other 50 ohm boards
  ...                   ...
8 modules                       15 other 50 ohm boards

2 connectors of the same module are about 3/4 inch apart.
2 connectors of different modules are about 5/8 inch apart.

        Module #1          Module #2
      |<-------->|<------>|<-------->|
          3/4"      5/8"

      0          0        0          0
      0          0        0          0
      0          0        0          0
      0          0        0          0
      ...        ...

What should the impedance of the backplane be?
50 ohms?  100 ohms?  800 ohms?


Regards, Doug

Private emails welcome

mailto:[log in to unmask]

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