[SI-LIST] Re: four S channels VNA
- From: "Thomas Beneken" <beneken@xxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 22 Jul 2005 12:06:24 +0200
Giovanni,
we do the same in our lab. But I would't call it a 4 port. It doesn't
deliver 4x4 s-parameter matrices, just 2x2 diff mode. You loose common mode
and mode conversion. Cal procedure seems ok.
If the hybrid delivers true diff mode to the DUT and in turn converts diff
to common only, then all is fine. But there will be some mode conversion in
the hybrids. Mode conversion in the DUT will contribute to the diff mode
readout, causing errors.
Thomas
> Message: 10
> Date: Thu, 21 Jul 2005 11:15:46 +0200
> From: "Guasti Giovanni" <Giovanni.Guasti@xxxxxxxxxx>
> Subject: 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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