PSS, PNOISE and other simulations for a circuit containing an oscillator and Mixer

Set up your input source to only generate one sine wave (not two sinusoids) and have it set the input power to (say) prf. On the same source, find the small-signal parameters and set pacmag to prf as well. 

In the hb analysis set the first tone to be your oscillator and the second to be the frequency of the large signal tone on your signal input. Then set up an hbac analysis and set this to be a single frequency (not a frequency sweep). The frequency should be that of the nearby frequency and will act as the second tone. The hbac outputs will give you the IM3 at 2*fhb2-fhbac (shifted by the LO frequency), and then this be used to compute the IP3 (there’s a choice under the hbac outputs on the direct plot form to do this). Unlike with 3-tone hb approach you only can get one of the IM3 outputs this way (since the hbac can only produce first-order side bands) but that’s normally fine as it’s usually symmetrical (and you can always swap the frequencies around on the source and the hbac analysis).

If this is unclear, please mention the frequency of the two input tones you’re using in your IP3 measurement and then (approximate) oscillator frequency and I can explain with some worked numbers which might make it clearer. (trying to explain when answering in my phone might be optimistic!)

Andrew

The frequencies were defined as:

• fhb1 = 4.9G
• fhb2 = 100M
• fhbac = 200M
• fosc = 4.90011G

Simulating IIP3 with HB + HBAC analysis and analyzing hbac_mt --> IPN curves --> Port (R(Port) fixed) --> Variable sweep = -30 --> IP3 input reference --> Select 3rd order harmonic (4.9 GHz) and 1st order harmonic (5.1 GHz) --> Select PORT output. When selecting the PORT of the mixer output, the IIP3 graph is not plotted.

An error message appears when selecting the PORT mixer output --> *ERROR* complex: argument #1 must be a number (template type = "n") - complex(nan, -nan)

In the HBAC simulation, the following warnings are checked:

WARNING: The result for relative frequency equal to 0 may be inaccurate.

WARNING (SPECTRE-16518): An arithmetic exception occurred in the analysis `sweephb-004_hbac'. Use the `+diagnose' command line option to get more information.

Could this issue be related to the Spectre version? Or something related to the Options form? I can't find any material related to this issue.

I don't quite understand your setup, because the frequencies don't make sense. So I put together a mixer with an oscillator for the LO, and had it configured as follows:

foscGuess: 1.9G (it actually converged as 1.829G)
fhb1: 1.904G
fhb2: 1.905G
prf: -30

The input port (RF) had two sine sources, with the power of both set to pro

I can then from just the hb measure the IP3 with the 3rd Order harmonic set to 74M and the 1st order harmonic as 76M.

If I then set fhb2 to 0, and ensure my source has the PAC magnitude (dBm) set to prf, and then run a two-tone HB (same setup as above) with hbac set to absolute, single point frequency at 1.905G, then everything runs. However, it appears that the small-signal input is not being applied, since all the results are at -6.4kdB (so essentially 0). Something has definitely not worked in this scenario, and I see the same errors as you when trying to plot the IPN curves, plus the same error reported by Spectre.

I can't find reports of this, I wonder whether anyone has actually tried to run semi-autonomous hb with hbac.

I'll raise this with SpectreRF R&D.

Regards,

Andrew

Thank you for your response. I look forward to receiving more feedback on this error.