Question on IP3 simulation in SpectreRF

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wangyufn

Joined: 29 Jul 2005
Posts: 29
Location: Shanghai, China

06 May 2008 5:58 difference between qpss and pss

There are several methods to simulate IP3 in SpectreRF.
1) PSS/PAC analysis
2) QPSS analysis
3) Rapid IP3 using PSS/PAC analysis
4) Rapid IP3 using AC analysis

What is the difference between them? And in different applications, how to make a choice of the proper method?

Can anyone help me? Thanks.

pancho_hideboo

Joined: 21 Oct 2006
Posts: 39
Helped: 3

06 May 2008 8:49 rapid ip3

wangyufn wrote:

There are several methods to simulate IP3 in SpectreRF.

First you have to understand a difference between PSS and QPSS.
PSS is one basis expansion.
QPSS is multi bases expansion.

For example, assume IP3 evaluation of amplifier where you drive two large signal tones as input.
If frequencys of two drive signals are set such that a fundamental frequency of PSS is relative large, you can do calculation of IP3 using only PSS.

If frequencys of two drive signals are set such that a fundamental frequency of PSS is fairly small, you can do calculation of IP3 using PSS/PAC or only QPSS.

wangyufn wrote:

3) Rapid IP3 using PSS/PAC analysis
4) Rapid IP3 using AC analysis

"Rapid IP3" is a perturbation of projection method based on Born approximation.

For mixer, use "Rapid IP3 using PSS/PAC".
For amplifier, use "Rapid IP3 using AC".

wangyufn wrote:

What is the difference between them? And in different applications, how to make a choice of the proper method?
Can anyone help me? Thanks.

About Cadence tool, you had better post in the following.
http://www.designers-guide.org/Forum/YaBB.pl?board=rfsim

DDavid

Joined: 06 Apr 2006
Posts: 232
Helped: 22

06 May 2008 13:42 difference between pss and qpss

Hi

PSS/PAC can't produce close products.
QPSS can work with close products.

David

wangyufn

Joined: 29 Jul 2005
Posts: 29
Location: Shanghai, China

06 May 2008 15:33 ip3 simulation

HI, pancho_hideboo & DDavid

I appreciate your reply very much. Thank you.

From my understanding, when using PSS+PAC to simulate IP3, one of the tone is regarded as large signal while the other is regarded as small signal. QPSS treats the both tones as large signals. Does it mean that QPSS is more suitable for mixer design? Is PSS+PAC more suitable for LNA design? It is said that PSS+PAC simulation time is long. Does it mean that it is more accurate?

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DDavid

Joined: 06 Apr 2006
Posts: 232
Helped: 22

06 May 2008 16:54 ac simulation rapid ip3

Hi,

1)
PSS - Large
QPSS Large/Moderate.

2)

Again when make IP3 u have to inject 2 tones:
f1 and f2

Δ=f2-f1 it's a delta between 2 tones.
If Δ is small (around a few MHz, exactly I can find if u need,
also it's depend on Fund F))
then u make QPSS simulation!

David