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https://designers-guide.org/forum/YaBB.pl Simulators >> RF Simulators >> PSD from envelope following analysis https://designers-guide.org/forum/YaBB.pl?num=1264078706 Message started by aaron_do on Jan 21st, 2010, 4:58am |
Title: PSD from envelope following analysis Post by aaron_do on Jan 21st, 2010, 4:58am Hi all, I ran an envelope following analysis on a MSK signal and it showed a peak voltage of 0.316V. Since this is a constant envelope signal, I expect the power of the signal to be about 0.316^2/100 = 1mW. However, when I plotted the PSD and integrate over the entire bandwidth, I get a power of about 1.7mW. Actually, since this is a modulated signal, I actually expect the signal to be even smaller. It should be approximately 0.316^2/(50*PAPR) I think. Can someone please shed some light on where i've made my mistake? thanks, Aaron |
Title: Re: PSD from envelope following analysis Post by aaron_do on Jan 21st, 2010, 6:24am by the way, when I ran the envelope following analysis on a simple PA, the PSD showed no change in shape from input to output. I don't think the PA is that linear so is there something I should know about the simulation setup which i'm not doing? thanks, Aaron |
Title: Re: PSD from envelope following analysis Post by pancho_hideboo on Jan 21st, 2010, 7:04am aaron_do wrote on Jan 21st, 2010, 4:58am:
Is it right ? Always describe vendor's name which you use as simulator and post processing. When I have spare time, I will confirm power using Post Processing Environment of Cadence. If results of Cadence Post Processing are not correct as you say, I will confirm power using RF golden standard Post Processing such as Agilent ADS for results of Cadence Spectre. aaron_do wrote on Jan 21st, 2010, 4:58am:
Assume vRF(t)=Real[Venv(t)*exp(j*ω*t)], Venv(t)=I(t)+j*Q(t) Instantaneous RF Power delivered to Load Rload is pRF(t)=vRF(t)2/Rload Instantaneous Envelope Power delivered to Load Rload is penv(t)=|Venv(t)|2/(2*Rload) PEP(Peak Envelope Power)=Max[|Venv(t)|]2/(2*Rload) Averaged RF Power=Average[pRF(t)]=RMS[vRF(t)]2/Rload Here there are two options for averaging, Averaging regarding Carrier and Averaging regarding Envelope. If RF signal is repeated burst wave, frame averaging can be also defined. RMS[vRF(t)]2=|Venv(t)|2/2 for Averaging regarding Carrier not Envelope. RF Power averaged regarding Carrier is =|Venv(t)|2/(2*Rload) This is no more than Instantaneous Envelope Power delivered to Load Rload, penv(t). RMS[vRF(t)]2=RMS[|Venv(t)|]2/2 for Averaging regarding Envelope. RF Power averaged regarding Envelope is =RMS[|Venv(t)|]2/(2*Rload) PAPR=PEP/RMS[|Venv(t)|]2/(2*Rload) So Average[pRF(t)] which is averaged regarding Envelope is Average[pRF(t)]=RMS[|Venv(t)|]2/(2*Rload)=PEP/PAPR=Max[|Venv(t)|]2/(2*Rload*PAPR) In your case, it is "0.3162/(2*50*PAPR)" not "0.3162/(50*PAPR)". aaron_do wrote on Jan 21st, 2010, 6:24am:
But a specification for spurious emission exists in "IEEE 802.15.4 standard". For ZigBee Application, we are not permitted to consume much current in PA, so clear ACPR degradation can be observed. Although I have not confirmed it by using Cadence Spectre in detail, generally clear ACPR degradation can be observed even if you use Cadence Spectre. For detail analysis purpose, I'm using Agilent GoldenGate and ADSsim with including noise effects. |
Title: Re: PSD from envelope following analysis Post by aaron_do on Jan 21st, 2010, 8:25pm I think I may be running the simulation wrongly. This is my first time using envelope following analysis so I may have made a beginner's mistake. Here are my settings: engine: Shooting Fund Frequency = 2.45G stop time = 500u number of harmonics = 1 Accuracy Defaults: moderate Also, when I plot the power versus time of the zeroth harmonic (at the supply), it is not much greater than the power versus time of the first harmonic (at the load). I don't think the PA is that efficient so i'm definately doing something wrong. Any help is appreciated. thanks, Aaron |
Title: Re: PSD from envelope following analysis Post by pancho_hideboo on Jan 22nd, 2010, 1:04am aaron_do wrote on Jan 21st, 2010, 4:58am:
So there is no problem regarding an implementation of psdbb() in Cadence ADE Post Processing. In Agilent ADS(RFDE) Post Processing Environment, generally I use following three functions for evaluation of Channel Power. http://edocs.soco.agilent.com/display/ads2009/spec+power%28%29 http://edocs.soco.agilent.com/display/ads2009/channel+power+vi%28%29 http://edocs.soco.agilent.com/display/ads2009/channel+power+vr%28%29 http://edocs.soco.agilent.com/display/ads2009/peak+to+avg+pwr%28%29#peaktoavgpwr%28%29-1107415 In the following, I use "spec_power()" to evaluate ACPR. http://www.designers-guide.org/Forum/YaBB.pl?num=1190971685/7#7 Attached figure is an input MSK signal for DUT such as Power Amplifier. Power evaluated as an integration of psdbb() is 0.97mWatt(=-0.15dBm). So PAPR=0.15dB I confirmed four windows, "Blackman", "Rectangular", "Hamming" and "Hanning". There is no difference between them. "test_aaron.ocn" Quote:
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Title: Re: PSD from envelope following analysis Post by pancho_hideboo on Jan 22nd, 2010, 1:40am aaron_do wrote on Jan 21st, 2010, 8:25pm:
http://www.designers-guide.org/Forum/YaBB.pl?num=1262000981 Also again see http://www.designers-guide.org/Forum/YaBB.pl?num=1263961579/2#2 aaron_do wrote on Jan 21st, 2010, 8:25pm:
try to use these actually well used envelope analysis. I'm using Agilent GoldenGate and ADSsim with including noise effects as reference of Envelope Analysis. aaron_do wrote on Jan 21st, 2010, 8:25pm:
It seems your Envelope Analysis of Cadence Spectre can converge without failure. Most probably you might have some mistakes in treating results of Envelope Analysis of Cadence Spectre. Do you correctly treat results of Envelope Analysis of Cadence Spectre ? For example, do you correctly understand "envlp_td" and "envlp_fd" ? You had better set "strobeperiod" if you use Envelope Analysis of Cadence Spectre to evaluate ACPR. |
Title: Re: PSD from envelope following analysis Post by aaron_do on Jan 22nd, 2010, 5:41am Quote:
this seems to be what i'm missing. I'll go back and do some more reading to see if I can figure out my misunderstanding...btw thanks for showing your plots thanks, Aaron |
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