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https://designers-guide.org/forum/YaBB.pl Simulators >> RF Simulators >> Why HB-QPSS's result is far different from ADS-HB? https://designers-guide.org/forum/YaBB.pl?num=1205223090 Message started by pancho_hideboo on Mar 11th, 2008, 1:11am |
Title: Why HB-QPSS's result is far different from ADS-HB? Post by pancho_hideboo on Mar 11th, 2008, 1:11am Hi. I've never used SpectreRF mainly for RF circuit. http://www.designers-guide.org/Forum/YaBB.pl?num=1125929808 http://www.designers-guide.org/Forum/YaBB.pl?num=1162921214/0#0 http://www.designers-guide.org/Forum/YaBB.pl?num=1170364605/2#2 http://www.designers-guide.org/Forum/YaBB.pl?num=1194765058/1#1 But design Kits I'm using now are provided as encrypted model file of Spectre only :'( I couldn't apply ADS(RFDE) for this Design Kits. :'( So I tried HB-QPSS-Ana of Cadence SpectreRF(Version 6.2.0.493 -- 19 Sep 2007). :-? But results of SpectreRF seemed to be very suspicious especially regarding accuracy. I compared ADS-HB and Cadence HB-QPSS using familiar netlist. Netlist is from ne600 which is well known in SpectreRF Training manual. Cadence HB-QPSS takes very long time for simulation and results of SpectreRF are far different from ADS results. The followings are extractions of log file from each simulator. Cadence HB-QPSS is slower than ADS by 5 times. >:( [Log from Spectre] Quote:
[Log from ADSsim] Quote:
I attached results of both simulator. Left one shows RF power v.s. Fundamental and IM3 output at IF node. Right one shows RF power v.s. derivative of left curve. Why IM3 results of Cadence HB-QPSS rolls off for low RF input level ? :( If I use shooting PSS, I often observed such roll offs at low RF input level. But this is HB not shooting.... Also why does Cadence HB-QPSS takes very long time although simulation conditions are almost same between ADS and SpectreRF ? Model file of BJT(rfModels.scs) Code:
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Title: Why HB-QPSS's result is far different from ADS-HB? Post by pancho_hideboo on Mar 11th, 2008, 1:43am Netlist of Spectre(qpss_hb3.scs) Quote:
Netlist of ADSsim(qpss_hb3.ads) Quote:
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Title: Re: Why HB-QPSS's result is far different from ADS Post by pancho_hideboo on Mar 11th, 2008, 3:04am I tried HB-QPSS without specifying "selectharm" and "maximorder" and with "restart=no" like following. IM3 curve of SpectreRF come not to show roll off at low RF input. But in this case, IM3 curve is upshifted by 8dB compared to ADS's result. And still simulation speed is slow. Memory consumption is huge. qpss qpss + harmonicbalance=yes + funds=["FLO" "FRF1" "FRF2"] maxharms=[5 5 5] oversample=[1 1 1] //+ selectharm=diamond maximorder=5 + errpreset=moderate //+ method=gear2only + annotate=status + restart=no + tstab=0n + maxperiods=200 [Log] Total time required for sweep analysis `sweepqpss' was 196.75 s (3m 16.8s). Aggregate audit (6:59:51 PM, Tue Mar 11, 2008): Time used: CPU = 198 s (3m 17.6s), elapsed = 200 s (3m 20.0s), util. = 98.8%. Time spent in licensing: elapsed = 90 ms. Virtual memory used = 59.1 Mbytes. spectre completes with 0 errors, 31 warnings, and 31 notices. |
Title: Re: Why HB-QPSS's result is far different from ADS Post by pancho_hideboo on Mar 11th, 2008, 4:22am I tried PSS(Shooting)/PAC. But results of IM3 curve doesn't match witn both QPSS(HB) and ADS(ADS). I think PSS(Shooting)/PAC result is most reliable. How do you think ? Netlist of Spectre(pss_pac.scs) Quote:
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Title: Re: Why HB-QPSS's result is far different from ADS Post by pancho_hideboo on Mar 12th, 2008, 4:33am Sorry, I mistook in specifying a mixing index for 3 tone HB-QPSS in figure, "hyottoko_qpss.jpg" and "aho_pss_pac.jpg". In these figure, I wrongly chose (1 2 -1) as mixing index. I should choose (1 1 -2) or (1 -2 1). But there is no mistake in first figure, "heppoko_qpss.jpg" which shows roll off at low RF input level. I attached correct figure. In this figure, I added HB 2tone with one tone small signal analysis results of ADS which is similar to QPSS(2tone)/QPAC. In Agilent ADS, "selectharm" is restricted to "diamond" although other options are provided as "selectharm" in new Agilent simulator, GoldenGate. But in Spectre, I must not select "diamond". If I don't specify "selectharm" and "maximorder" and do set "restart=no" in Cadence HB-QPSS, it seems that I can get relative reasonable results from 3 tone HB-QPSS of Cadence Spectre. But I think simulation speed is very slow and memory consumption is huge compared to ADS. [Netlist of HB 2tone with one small signal Analysis in ADS] qpss_hb2ss.ads Quote:
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Title: Re: Why HB-QPSS's result is far different from ADS Post by yzhu on Mar 12th, 2008, 5:12pm Hi, 1. HB has much lower numeric noise level, so it should not give roll off at low Prf. That "roll off" may be caused by a bug in SpectreRF's "diamondcut". So SpectreRF has to use the regular "boxcut", it could be a little slower. 2. Even I use boxcut, I can finish it much faster than yours and use only 17.6MB. Aggregate audit (4:45:54 PM, Wed Mar 12, 2008): Time used: CPU = 141 s (2m 21.1s), elapsed = 142 s (2m 22.0s), util. = 99.3%. Time spent in licensing: elapsed = 10 ms. Virtual memory used = 17.6 Mbytes. 3. Don't compare shooing PSS+PAC with ADS's HB. Shooting is only for strongly nonlinear circuits like SCF. You should try SpectreRF's 2Tone QPSS+QPAC, and compare it with ADS. I ran Spectre and finish in 13 seconds and guess it is much faster than ADS. My setting is: sweeppss sweep param=prf + start=-40 stop=0 step=5 + values=[-17.5 -12.5 -7.5 -2.5] { qpss qpss + harmonicbalance=yes + funds=["FLO" "FRF1"] maxharms=[5 5] oversample=[1 1] //+ selectharm=diamond maximorder=5 + errpreset=moderate //+ method=gear2only + annotate=status + restart=no + tstab=0n + maxperiods=200 qpac qpac values=[frf2] sidevec=[-1 0 1-2] annotate=status freqaxis=absout } So the conlusion is SpectreRF should verify their "diamondcut". Other than that, SpectreRF is better than ADS. YZ |
Title: Re: Why HB-QPSS's result is far different from ADS Post by pancho_hideboo on Mar 12th, 2008, 11:22pm Quote:
Even in HB-QPSS of SpecreRF, "diamond" is default setting of selectharm when maximorder is set. So "selectharm=diamond" has to be reliable. Quote:
The reason why I use PSS(Shooting)/PAC as reference is that there is no issue about setting order, mutual order and selectharm in PSS(Shooting)/PAC. So I think results of PSS(Shooting)/PAC is most reliable except for small and large RF input level. I don't compare speed and memory consumption of PSS(Shooting)/PAC with HB-Analysis. Quote:
Maybe your computer is superior than mine. But still speed is slow by 3 times than my 3 tone HB using ADS. Again I list results of benchmark. Quote:
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Title: Re: Why HB-QPSS's result is far different from ADS Post by pancho_hideboo on Mar 12th, 2008, 11:30pm Quote:
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Compare (1) and (2) with (4), these are 3 tone HB Analysis. And compare (3) with (5) and (6), these are 2 tone HB with one small signal Analysis. HB-QPSS is apparently slow compared to ADS in all cases. In 3 Tone HB-QPSS, memory consumption is huge and simulation speed is veryl slow. In 2 Tone HB-QPSS/QPAC, memory consumption is almost same as ADS but simulation speed is still slow. Quote:
I've heard such claim regarding not only speed but also accuracy from Cadence many many times since shooting PSS/QPSS days. The followings are my conclusion. In 3 Tone HB-QPSS, memory consumption is huge and simulation speed is very slow. In 2 Tone HB-QPSS/QPAC, memory consumption is almost same as ADS but simulation speed is still slow. Now my first problem that only encrypted Spectre models are provided from foundary is resolved. Foundary provided me model file for ADS(RFDE). And I'm now moving to GoldenGate from ADS(RFDE). So I don't use HB-QPSS of SpectreRF. :P I've evaluated HB analysis in SpectreRF using 6.0USR1, 6.0USR2, 6.1, 6.2 versions. In addition to supporting autonomous QPSS, I expect any remarkable improvement of HB analysis in SpectreRF at 6.3 or later versions. 8-) |
Title: Re: Why HB-QPSS's result is far different from ADS Post by pancho_hideboo on Mar 18th, 2008, 4:49am Recently I've updated ADS from ADS2006Update3 to ADS2008. The followings are benchmark results of ADS2008. hpeesofsim (*) 2008.500 Jan 22 2008 (built: 01/22/08 22:43:36) Copyright Agilent Technologies, 1989-2008. ADS is little improved from ADS2006Update3 and very very fast compared to HB-QPSS of SpectreRF. Now I have GoldenGate, I expect more superior performance of GoldenGate. Quote:
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