[SI-LIST] Re: The Ground of VNA
- From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <zhang_kun@xxxxxxxxxx>, "si-list" <si-list@xxxxxxxxxxxxx>
- Date: Tue, 18 May 2004 07:18:27 -0400
Dear Zhangkun,
High-frequency instruments use single-ended connections;
most of the differential inputs and outputs are also formed
of individual single-ended connections. When you make
the connection from a VNA to the DUT with two cables,
you make a ground loop. The ground loop creates a
problem only at low frequencies, where the resistance of
the cable braid dominates the return-path impedance.
At high frequencies (with most cables above a few MHz),
the inductance of the cable braid opens the ground loop
so much so that you can cross-connect the cables by
connecting the hot side of cable1 to the ground side of
cable2 and hot side of cable2 to the ground side of cable1
and under some circumstances you will hardly notice the
difference in the response.
Regards,
Istvan Novak
SUN Microsystems
----- Original Message -----
From: "Zhangkun" <zhang_kun@xxxxxxxxxx>
To: "si-list" <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, May 18, 2004 5:12 AM
Subject: [SI-LIST] The Ground of VNA
> Dear All
> Could you tell me the details about the ground of VNA? From the
experiment, I could find out that the ground of two ports of VNA are
connected. However, I do not know the detail.
>
> This is critical for some kind of analysis. For example, there is no
ground plane.
>
> Best Regards
>
> Zhangkun
> 2004.5.18
>
>
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