The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> RF Design >> Can I do frequency sweep in PSS?
https://designers-guide.org/forum/YaBB.pl?num=1167111962

Message started by zhangjerome on Dec 25^th, 2006, 9:46pm

Title: Can I do frequency sweep in PSS?
Post by zhangjerome on Dec 25^th, 2006, 9:46pm

I am now designing a mixer with fixed IF. Since the bandwidth is relatively large, I want to sweep the LO and RF frequency.
I don't know how to do this since in PSS I must set the beat frequency. Once the RF and LO frequency is swept, the beat frequency
will not be constant.

Can anyone tell me what to do ?

Title: Re: Can I do frequency sweep in PSS?
Post by ACWWong on Dec 27^th, 2006, 6:23am

The pss fundamental (beat frequency) can be setup as a design variable and then swept in a paramteric analysis quite easily achieve a swept frequency pss.
But in your case I would ask you what simulation you are actually trying to do ?
If you really want large signal LO & non-small-signal RF and have a fixed IF frequency, then the IF will be non-small tone so you would try to choose the pss beat frequency as the IF frequency (assuming its quite large, otherwise the simulation will be very ineffiecient).
If having done this, then you could now quite simply parametrically sweep LO and RF frequency in IF Frequency steps to cover your LO/RF frequency range of interest, so that the pss beat frequency does not change between runs.

Title: Re: Can I do frequency sweep in PSS?
Post by zhangjerome on Dec 27^th, 2006, 9:36pm

ACWWong

Thankyou so much for your help.

Title: Re: Can I do frequency sweep in PSS?
Post by Andrew Beckett on Jan 15^th, 2007, 6:59am

Note that you can also sweep one of the frequencies (say the LO or the RF) using the sweep on the PSS form - and the other using the parametric analysis form.

For the beat frequency, put some nominal value (it doesn't really matter - just do auto-calculate, perhaps).

Then in the Options form, down the bottom, there is a field labeled "Additional Parameters". Enter "autofund=yes" in that field.

You need to be using at least IC5141 USR2 or later for the additional parameters field to be present. And you need to be using spectre from MMSIM60 or later for pss to support autofund. This tells pss to calculate the pss fundamental from the sources in the circuit, rather than using a specified fundamental frequency. The one place this won't work is if you have a divider in the circuit - if you do, then add a dummy source in the circuit at the divided down frequency.

Regards,

Andrew.