[SI-LIST] four S channels VNA

dear all,
our laboratory bought two hibrid junctions a long time ago. I am trying =
to obtain a four S channels VNA, placing the hibrid junctions in series =
to our two S channel VNA. I would like to realize some differential =
scattering measurements (at the moment we couldn't buy a new 4 channel =
VNA).=20
How would you calibrate the whole system? Do you know any article, =
paper, web-site where I could read more about it? Do you think a =
differential to common mode coupling could affect the measurement?
I'm waiting for all your objections. ;-)
Thankyou all,
        Giovanni

             HJ +90=B0    |------|       HJ -90=B0
                |-------| diff |-------|
  VNA S1-------<        | DUT  |        >------- VNA S2
                |-------|      |-------|
                        |------|
             HJ -90=B0                   HJ +90=B0
                       =20
                        ^      ^
                        |      |
                      sect1   sect2

all cables have same length,
all cables have Z0=3D50ohm
Hibrid Junctions have a bandwidth B - so the measure will be
done in B
-----------------------------------------------------------
open (S2 is symmetrical)
             HJ +90=B0   =20
                |-------High impedance
  VNA S1-------<       =20
                |-------High impedance
                       =20
             HJ -90=B0   =20
-----------------------------------------------------------
short (S2 is symmetrical)
             HJ +90=B0   =20
                |-------0ohm
  VNA S1-------<       =20
                |-------0ohm
                       =20
             HJ -90=B0      =20
-----------------------------------------------------------
50ohm (S2 is symmetrical)
             HJ +90=B0   =20
                |-------50ohm
  VNA S1-------<       =20
                |-------50ohm
                       =20
             HJ -90=B0      =20
-----------------------------------------------------------
through
             HJ +90=B0           HJ -90=B0
                |--------------|
  VNA S1-------<                >------- VNA S2
                |--------------|
                       =20
             HJ -90=B0           HJ +90=B0
                       =20
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