[SI-LIST] Re: From spectrum of i(t) to spectrum of d(i(t))/dt
- From: "Ihsan Erdin" <erdinih@xxxxxxxxx>
- To: a.ingraham@xxxxxxxx
- Date: Fri, 18 May 2007 23:26:16 -0400
The differentiation in amperes is not amperes but not unitless,
either. The time derivative of the current simply results in "voltage"
-after a correction factor with the inductance of the medium. The 180
dB increase at 1Ghz is actually on the ratio of the voltage to the
current, which is "impedance". So, everything is consistent.
Regards,
Ihsan
On 5/18/07, Andrew Ingraham <a.ingraham@xxxxxxxx> wrote:
> > I have some questions on the spectrum translation. Recently, I measured
> > the spectrum of power supply current i(t) ( very long time range ) with
> > current probes, then I would like to transfer it to the spectrum of di/dt. I
> > know thoeretically F( di(t)/dt ) = j w F ( i(t) ). My question is : Does it
> > mean at every frequency point, the spectrum level is multiplied by the
> > corresponding frequency for di/dt signal ? If this is the case, the I end
> > up with quite large spectrum value in di/dt which is definitly not
> > reasonable. For instance, at 1 GHz, the spectrum level is increase by 180
> > dB. I am quite confused about this. Is my derivation wrong ?
>
> Yes, it is correct; no your calculation is not wrong.
>
> Take care of your units! When you differentiate amperes, the result is not in
> amperes. The spectrum contribution at 1 GHz doesn't increase by 180 dB
> because that would be "comparing apples to oranges," even though the raw
> (unit-less) numbers might happen to be that way.
>
> 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
Other related posts:
