David. I was mistaken. Taht's what I get for not looking closely at the deck. However your rise time is only 1/20th of the RC time constant so the result that you will get from the transient will have little difference than one with a zero rise time. Steve. On 9/2/2011 9:48 AM, David Banas wrote: > "You are not driving your transient with a step" > > Why do you say that? > -db > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On > Behalf Of steve weir > Sent: Thursday, September 01, 2011 6:40 PM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Impulse vs. Step Response? > > As long as the frequency / time domain conversions cover a wide enough > frequency range the FD response and the FFT of the unit impulse should > match. You are not driving your transient with a step so there should > not be a need to consider > > U(w) = H(w)/jw > > Steve. > On 9/1/2011 5:40 PM, David Banas wrote: >> Hi all, >> >> I've got a puzzler. I'm using this HSpice deck: >> >> .TITLE AC Sweep vs. Transient Correlation >> >> .OPTION >> + POST >> + PROBE >> + RUNLVL = 5 >> >> Rin in out r=1K >> Cout out 0 c=1pF >> Rout out 0 10MEG >> >> Vin in 0 DC 1 AC 1 >> >> .IC V(out) = 0 >> >> .AC DEC 10 1 1G >> .TRAN 0.05n 1u 0 0.05n UIC >> >> .PROBE AC V(in) V(out) >> .PROBE TRAN V(in) V(out) >> >> .END >> >> to get both the transfer function, H(w), (.AC command) and the unit step >> response, u(t), (.TRAN command) of a simple RC LPF. >> >> Then, I take the FFT of the .TRAN output and compare it to the .AC output. >> And they match! >> >> I wasn't expecting a match, since all my textbooks say there's a `jw' factor >> relating the impulse response and the step response. That is: >> >> U(w) = H(w)/jw >> >> So, when I compared the 2 spectra, I was expecting the FFT of my .TRAN >> output to have an extra 6dB/octave roll-off, as compared to the .AC output, >> due to the `w' in the denominator, above. >> >> Can anyone shed some light on this? >> >> Thanks, >> >> David Banas >> Sr. Member Technical Staff >> Altera >> +1-408-544-7667 - desk >> >> Did you know Altera offers over 150 free online technical training courses? >> Take one today! >> >> >> Confidentiality Notice. >> This message may contain information that is confidential or otherwise >> protected from disclosure. If you are not the intended recipient, you are >> hereby notified that any use, disclosure, dissemination, distribution, or >> copying of this message, or any attachments, is strictly prohibited. If >> you have received this message in error, please advise the sender by reply >> e-mail, and delete the message and any attachments. Thank you. >> >> ------------------------------------------------------------------ >> 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 >> >> Old (prior to June 6, 2001) list archives are viewable at: >> http://www.qsl.net/wb6tpu >> >> >> > > -- > Steve Weir > IPBLOX, LLC > 150 N. Center St. #211 > Reno, NV 89501 > www.ipblox.com > > (775) 299-4236 Business > (866) 675-4630 Toll-free > (707) 780-1951 Fax > > > ------------------------------------------------------------------ > 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 > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > > Confidentiality Notice. > This message may contain information that is confidential or otherwise > protected from disclosure. If you are not the intended recipient, you are > hereby notified that any use, disclosure, dissemination, distribution, or > copying of this message, or any attachments, is strictly prohibited. If you > have received this message in error, please advise the sender by reply > e-mail, and delete the message and any attachments. Thank you. > > ------------------------------------------------------------------ > 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 > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > -- Steve Weir IPBLOX, LLC 150 N. Center St. #211 Reno, NV 89501 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax ------------------------------------------------------------------ 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 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu