[SI-LIST] Re: Power sum crosstalk calculation method--is there an error in OIF-CEI or 10GBase-KR?
- From: Vinu Arumugham <vinu@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 29 Jul 2013 10:29:10 -0700
Bruce,
I think the equation defined in OIF - CEI needs no changes.
S-parameters are just a ratio. You can get the voltage or power ratio
from them as needed.
PSXT = -37dB for two -40dB aggressors is correct.
If the aggressors were in phase, and you wanted the absolute worst case
summation, you would use voltage sum crosstalk (VSXT).
The -34dB you calculated is VSXT not PSXT.
Thanks,
Vinu
On 07/29/2013 02:26 AM, Qin, Zhenshui (NSN - CN/Shanghai) wrote:
> 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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