flexible balance parameter setup in PSS

[wolf6873]

Hi, everybody,

I am runing the PSS simulation with the felible balance method, can
anybody tell me how to setup and the oversample factor and what's the
meaning of that?

THanks

Norman

 

[Andrew Beckett]

On Thu, 19 Jul 2007 19:21:33 -0000, wolf6873 <xingnw@gmail.com> wrote:

Hi, everybody,

I am runing the PSS simulation with the felible balance method, can
anybody tell me how to setup and the oversample factor and what's the
meaning of that?

THanks

Norman

Well, the oversample factor is not that commonly needed. It's used in the case
where you have aliasing caused by the fact that the highest frequency you're
using in the PSS (i.e. the highest harmonic you're asking for) is lower than the
highest significant frequency that is being generated by the circuit - resulting
in aliasing.

This of course can be solved by increasing the number of harmonics, but
sometimes if those harmonics are not too large, you can simulate more
efficiently by oversampling instead. It's not a substitute for having sufficient
harmonics, but it can improve accuracy more efficiently when you're getting some
aliasing.

Shooting doesn't suffer from this problem, because it naturally follows high
frequency waveforms due to it being performed in the time domain.

The case when you tend to get aliasing is when you are trying to do a multi-tone
simulation in harmonic balance PSS - but you've not asked for anywhere near
enough harmonics. In most cases you should use harmonic balance QPSS
instead, where you can manage the number of harmonics of each tone
separately.

So, there are very few cases when you need to use oversample factor.

Regards,

Andrew.
--
Andrew Beckett
Senior Solution Architect
Cadence Design Systems, UK.