[time-nuts] Is there any way to use a TIC to measure time of reflection on a PCB?

[Jim Lux]

On 1/23/13 6:48 AM, David Kirkby wrote:
> There's a fairly interesting (to me at least), discussion on an
> Agilent forum devoted to the calibration of vector network analyzers.
>
> http://www.home.agilent.com/owc_discussions/thread.jspa?threadID=34809&tstart=0
>
> The title of the thread is "Coefficients of fringing capacitance polynomial"
>
> A student needs to find the open-circuit fringing capacitance of a
> piece of microstrip line. For this he needs to know the time between
> the reference plane of the SMA connector and the open circuit
> microstrip.

Can he build multiple microstrips with known distances, and measure them 
all and solve for it that way?


>
> An obvious way to do this is with a vector network analyzer with a
> time-domain option. In HP/Agilent VNAs, this is option 010. The
> student has access to an obsolete and unsuported HP 8753C 6 GHz VNA,
> but it does not have the time-domain option.

Does it have the "measurement plane offset" option? I'm not in front of 
my old analyzer in the lab (8720C.. no disk drive), and it does have the 
transform option, but I'm not sure you need that option to have the 
"dial  an offset" in the calibration.  I've used that to move the 
reference plane from the connectors at the edge of a board to the device 
on the board: testing a vector modulator with the display in polar 
coordinate mode, for instance.. you keep turning the knob til the 
display is a dot, not a circle or arc.



>
> I thought he might be able to convince someone at Agilent to give the
> uni this option, which is just enabled by software. So far that has
> not worked. I did offer to help with access to my HP 8720D VNA which
> has the time-domain option.
>

What measurement uncertainty is called for here?  Can you make your own 
limited purpose cal kit? The open is the challenge.  Shorts, loads, and 
thrus are fairly straightforward. Maybe you have to collect the 
uncalibrated data with the cal standards and do the "cal" in post 
processing in Matlab or something.