Re: [802.3_100GCU] Return loss waveform at TP0a and TP5a

[Liav Ben Artsi <liav@xxxxxxxxxxx>]

Hi Ed,

If I understand your suggestion correctly,

I find this suggestion very interesting.

This correlates somewhat to fitted and ILD characteristics...

The waviness is board test fixture induced. limiting this can also help one know that the measurement is good enough...

However,

To contradict everything I wrote above, I think that the need for such a definition should take into account that:

1. the amount of board fixture ILD is limited in the spec.

2. if a device passes the measurement with higher board induced waviness, the device, to my understanding, is only better. connected to a better fixture it would pass with higher margin.

What do you say?...

thank you,

Best Regards,
Liav

Sent from my mobile phone

Ed Sayre <esayre@xxxxxxxx> wrote:

Liav:

 

I am concerned at the extent of the peak to valley variations seen in the Return Loss characteristics below.  I think that a peak-to-peak vs. local average value might be a good metric.to include.  I will work up a couple of test cases to get some numbers.

 

ed

 

Dr. Edward P. Sayre, P. E.

North East Systems Asscoiates, Inc.

9 Maple Lane

PO Box 807

Marshfield, MA  02050  USA

[T]: +1-781-837-9088

[C]: +1-978-314-4940

[E]: esayre@xxxxxxxx

 

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From: Liav Ben Artsi [mailto:liav@xxxxxxxxxxx]
Sent: Wednesday, October 17, 2012 12:15 PM
To: STDS-802-3-100GCU@xxxxxxxxxxxxxxxxx
Subject: [802.3_100GCU] Return loss waveform at TP0a and TP5a

 

Hi All,

 

During the Geneva interim a normative Tx/Rx specification at TP0a/TP5a was adopted and incorporated in:

93.8.1.4 Transmitter output return loss

93.8.2.2 Receiver input return loss

94.3.12.4 Transmitter output return loss

94.3.13.2 Receiver input return loss

 

This specification was intended to correlate to the package return loss as specified for COM @TP0 and TP5. These are specified in:

Table 93?8―Channel operating margin parameters

Table 94?17―Channel operating margin parameters

 

A concern was brought up that the extrapolation of the package return loss values from the device pins to TP0a and TP5a:

1.      took into account the extra waviness of the return loss.

But:

2.      Gave extra non relevant margin to the low frequency return loss

 

I find this concern very reasonable and therefore suggest to fix the limit at TP0a and TP5a to take into account that the test fixture has very minimal loss @ low frequencies.

The way I suggest doing that is by defining the following two sections of return loss:

RL(f) ≥ 6.25*f+10.3125 ; 0.05<f<3 ; f in GHz

  

 

I will be referencing this E-mail in the suggestion resolution to the comment I will be submitting.

Inputs are welcome (let’s have the debate here and save the time in Tx J).

 

Best regards,

--Liav