hbnoise: difference between sweep-type relative harmonic=0 and absolute

I meant to reply to this the other day. It sounds strange and I don't recall seeing this before. I'd be surprised if it's a bug in the simulator.

There's not really enough information to go on. Can you please provide:

1. The exact subversion of spectre you're using
2. The analysis statements from the bottom of the input.scs (ideally the parameters at the top of the netlist too if you're using any of those in the analysis setup)

Regards,

Andrew.

Hi Andrew,

Thanks for your response!, I am using IC6.17.713_SPECTRE16.10.284. The node I am plotting is the one from hbnoiseOut1. Thanks in advance!


simulator lang=spectre
global 0
parameters harm=9 flo=2G prf=-50
include "netlist"
simulatorOptions options reltol=5e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \
tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \
digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
dochecklimit=yes checklimitdest=both
dcOpCheckLimit checklimit checkallasserts=yes severity=none
dcOp dc write="spectre.dc" homotopy=dptran maxiters=150 maxsteps=10000 \
annotate=status
dcOpInfo info what=oppoint where=rawfile
hb hb tstab=80n saveinit=yes autosteady=yes oversample=[2]
+ fundfreqs=[(flo/2)] maxharms=[harm] errpreset=moderate
+ tstabmethod=gear2only annotate=status
+hbstb hbstb start=10 stop=300M dec=20
+annotate=status
hbac hbac sweeptype=relative relharmvec=[1] start=10 stop=300M
+ dec=30 maxsideband=3 annotate=status
hbnoiseOut1 ( vop von )
+ hbnoise sweeptype=relative relharmvec=[0] start=1k stop=200M
+ dec=5 values=[10 100] iprobe=PORT1 refsideband=[0]
+ noisetype=timeaverage noiseout=[am pm usb lsb]
+ separatenoise=yes annotate=status krylov_max_iter=400
hbnoiseOut2 ( vop2 von2 )
+ hbnoise sweeptype=relative
+ relharmvec=[0] start=1k stop=200M dec=1 values=[10 100 100k]
+ iprobe=PORT1 refsideband=[0] noisetype=timeaverage noiseout=[am
+ pm usb lsb] separatenoise=yes annotate=status
+ krylov_max_iter=400
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
asserts info what=assert where=rawfile

Hi Andrew,

I delayed my reply until I did further investigations. First, The above error disappeared and I couldn't reproduce it. It disappeared after creating new maestro veiw!

Regarding your reply, I did noise sim "ALL" not "USB", as I was simulating phase noise simultaneously for other nodes (LO signal of a receiver) together with the Rx output at baseband (relative harmonic=0) or absolute (while sweeping the target baseband frequency range).

I expected that regardless of ALL or USB, for the baseband signal, should get the same result. The issue is that when plotting USB noise after doing USB-noise sim or ALL-noise sim, I get different results. This I cannot understand. Also when plotting the noise summary, different components are having different contribution for ALL and USB noise sims. So which one can I trust?

Thanks for your support!

Best regards,

Ahmed.

Ahmed,

I can't think of a good reason why you'd get different USB noise results between running USB or ALL mode - that doesn't make sense to me. I think we'd need to look at this via customer support to understand whether it's a usage issue or a bug.

Regards,

Andrew.

Hi Andrew,

Thanks for your reply. I escalated this inside my company. My colleagues from the methodology department is tackling the issue. They will probably escalate it to Cadence support team. Thanks for your time!

Best regards,

Ahmed.