[SI-LIST] Re: Power sum crosstalk calculation method--is there an error in OIF-CEI or 10GBase-KR?
- From: "Qin, Zhenshui (NSN - CN/Shanghai)" <zhenshui.qin@xxxxxxx>
- To: "weirsi@xxxxxxxxxx" <weirsi@xxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 29 Jul 2013 09:26:46 +0000
Hi Steve,
Yes, I am working on electrical signal. So should I change the equation defined
in the OIF-CEI mask when calculating the power sum crosstalk?
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of ext steve weir
Sent: Monday, July 29, 2013 5:14 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Power sum crosstalk calculation method--is there an
error in OIF-CEI or 10GBase-KR?
10 log(10) (power ratio) gives dB power correctly. If you are working
with optical signals then you are working with optical power values and
10 log(10)(power ratio) is the correct expression. If you are working
with electrical signals, 20 lot(10)(voltage ratio) gives dB power for
voltages working into the same reference impedance.
Steve.
On 7/29/2013 1:57 AM, Qin, Zhenshui (NSN - CN/Shanghai) wrote:
> Hi,
> I am working on an simulation for 25G operation, the results is targeted to
> meet CEI 25G LR mask.
> An interesting thing I found in OIF-CEI 25G mask is the method used to power
> sum the crosstalk sources, actually the same method use also for IEEE
> 10GBase-KR standard.
> For example, If I have two crosstalk source, the equation should be like
> below:
> PSXT=-10*log10(10^(-Xtk1/10)+10^(Xtk2/10))
> But my question is, in SI area, our S-parameter is calculated using Voltage
> rather than Power, it means we calculate the value use
> S12 *log10(Vout/Vin).
> So the problem happened when we use the equation above, two -40dB crosstalk
> add up to
> PSXT=-10*log10(10^(-40/10)+10^(-40/10))=-37dB
> While the reasonable value should be -40dB corresponding to 0.01, and two of
> them makes 0.02, so
> PSXT *log10(0.02)=-34dB
>
> Does anyone know the trick behind the equation? Or what's wrong with my
> understanding?
> Thanks.
>
>
> Bruce
>
>
>
>
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