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 >> >> >> >> >> ------------------------------------------------------------------ >> To unsubscribe from si-list: >> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >> >> or to administer your membership from a web page, go to: >> //www.freelists.org/webpage/si-list >> >> For help: >> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >> >> >> List forum is accessible at: >> http://tech.groups.yahoo.com/group/si-list >> >> List archives are viewable at: >> //www.freelists.org/archives/si-list >> >> Old (prior to June 6, 2001) list archives are viewable at: >> http://www.qsl.net/wb6tpu >> >> >> > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu