Hello Andy, I do mean the first situation. In my measurements, the core circuit size, the input data and the clock frequency are fixed, the only parameter I play is VDD. If I plot PSD of power supply current in dBuV (X axis is frequency, in log scale), then the relationship is perfectly linear. Is that right, reasonable ? are there any theory on this ? regards, Junfeng On 6/29/07, Andrew Ingraham <a.ingraham@xxxxxxxx> wrote: > > > Generally speaking , what is the relationship between the digital > > circuits radiated emission( peak emission or maybe RMS ?) and the > supply > > voltage ? I could not find an exact answer for this. Maybe you guys here > > can > > educate me ! Thanks, > > This is a pretty open question. Perhaps you could clarify. > > Do you mean, given a fixed circuit, how do radiated emissions vary as we > vary the supply voltage? (Generally speaking, higher Vdd means higher > currents, and tends to cause faster switching times, both of which will > lead > to greater emissions.) > > Or do you mean something like the following: As supply voltages have > decreased over the years, what is the relationship between radiated > emissions and the nominal Vdd? > > Or in a more specific case, if we were to do 'ideal' scaling applied to > CMOS > (where all parameters scale in step with one another according to certain > defined relationships) how to radiated emissions vary with that scaling? > > The latter two are not easily answered. I'm guessing you mean the first. > > Regards, > Andy > > > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > 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 technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu