[hpsdr] ATLAS TDR & VNA Test Results

[Ray Anderson]

We had an all day network outage here yesterday so I was incommunicado
for the most part, however I did manage to go hide out in the lab for an
hour or so and do some VNA and TDR tests on the ATLAS board.

 

No problems detected. Everything looked about how I was expecting it to
look except my earlier impedance predictions by way of field solver were
off a bit from the measured impedance values apparently due to some
wrong assumptions that were made in setting up the extractor problem.

 

 

I plan on posting some plots to the web site later today or tomorrow,
however here is the bottom line:

 

 

I performed TDR and VNA measurements on all [0:24]  lines in both the X
and Y busses. All buss lines in each buss looked similar.

 

 

TDR Measurements:

 

X buss:

            Measured impedance : 40 ohms average (predicted 78.5)

 

Y buss

Measured impedance : 46.2 ohms average  (predicted 58)

 

The above measured impedances should be just fine for most applications
and probably workable for LVDS signal if the need should arise.

 

 

 

VNA Measurements:

 

X buss:

 

Measured from DIN connector 1 to 6

Ripple 6 dB p-p from DC to 1.5 GHz

Major Resonances begin occurring at 1.5 GHz (-50dB @ 2.1 GHz)

 

Y buss:

 

Measured from DIN connector 1 to 6

Monotonic rolloff down to about -8db DC to 1GHz

Ripple 6dB p-p 1GHz to 1.5 GHz

Major Resonances begin occurring at 1.5 GHz (-47dB at 2.1 GHz)

 

 

 

So based on:

Lack of assembly issues  (Phil, Chris Ray)

Lack of PS issues (Chris)

Lack of significant SI issues (Ray)

 

 

I'd say we are go for a production build.

 

Thanks to Chris for the assembly instructions and BOM and to Horst for
the refined assembly instructions and the EU BOM!

 

 

73,        Ray   WB6TPU

 

 

 

 

 

 

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