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weigiho

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Questions about Mixer NF simulation.
Apr 16^th, 2009, 4:42pm

Hello:
I have a mixer with LO=1GHz. The RF input=1.01GHz and the IF is at 10MHz. If in the pnoise simulation, I set the fund=1GHz and reference sideband=-1 and max sideband=10 I can get a reasonable NF. However, if I set the fund=10MHz and reference sideband=-111, max sideband=700 then the NF is very off. Is there any method such that even I set fund=10MHz can give me the correct NF in this situation. Thanks.

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pancho_hideboo

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Re: Questions about Mixer NF simulation.
Reply #1 - Apr 16^th, 2009, 10:26pm

You have to show tool's name you use. There are various vendor's simulators.

Show me tool's name you are using.
How many large signal tones do you use in master steady state analysis, one tone large or two tones large ?

weigiho wrote on Apr 16^th, 2009, 4:42pm:

I have a mixer with LO=1GHz. The RF input=1.01GHz and the IF is at 10MHz.
If in the pnoise simulation,
I set the fund=1GHz and reference sideband=-1 and max sideband=10 I can get a reasonable NF.
However, if I set the fund=10MHz and reference sideband=-111, max sideband=700 then the NF is very off.

Show me your netlists regarding analysis statement and signal source.

Although I don't know what simulator you use and don't know how many tones you use as large signal in master steady state analysis,
I think you should set reference sideband=-100, max sideband=1000 in latter case.

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Ken Kundert Global Moderator Offline Posts: 2384 Silicon Valley	Re: Questions about Mixer NF simulation. Reply #2 - Apr 17^th, 2009, 1:18am Weigiho, Why are you asking this question? Why are you not happy with the answer you are getting with fund=1GHz? What is it that you are trying to do? -Ken
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weigiho

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Re: Questions about Mixer NF simulation.
Reply #3 - May 4^th, 2009, 12:14pm

Actually I found something strange in simulating the NF of a superhetreodyne receiver.
My RF=1.021GHz, LO1=1GHz, IF1=21GHz, LO2=20GHz, and baseband=1MHz. I use the following code to simulate its NF

pss fund=20M harms=0 errpreset=conservative tstab=5u
+ saveinit=no method=gear2only tstabmethod=gear2only maxacfreq=20G
+ annotate=status
pnoise ( Out\+ Out\- ) pnoise start=500k stop=10M step=1M
+ maxsideband=500 iprobe=PORT0 refsideband=-51 annotate=status

1.The way I applied the input is shown in the attached file. I am not sure whether I should use egain=+/- 0.5 or +/-1 for RF input, but I use +/-1 anyway.
2.The input of the mixer is not matched to 50 ohm.
3.The output of the mixer is not matched to 50 ohm.
4.When I use results-->direct plot-->mainform-->......to plot the NF, it shows NF=13.34dB at 1MHz.
5.When I use results-->print-->noise summary, I got something in the following
Device Param Noise Contribution % Of Total
/PORT0 rn 2.39115e-10 21.84
/N8 id 1.38898e-10 12.69
/N4 id 1.38898e-10 12.69
Spot Noise Summary (in V^2/Hz) at 1M Hz Sorted By Noise Contributors

I calculate the NF=10*log(1/0.2184)=6.6075dB. Is this right?

Why these 2 results are different? How should I correctly give the input to the superhytereodyne receiver? Is the egain=1 correct? Do I have to put 2 seperate ports as input? Does input/output matching matter? I really have no idea. Can you kindly help me with this? Thanks very much.

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pancho_hideboo

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Re: Questions about Mixer NF simulation.
Reply #4 - May 4^th, 2009, 11:43pm

You are appending completely new questions without responding to the following.
http://www.designers-guide.org/Forum/YaBB.pl?num=1239925339/1#1

From contents of this new questions, you should append this new questions to the following your another post.
http://www.designers-guide.org/Forum/YaBB.pl?num=1239389950

weigiho wrote on May 4^th, 2009, 12:14pm:

Actually I found something strange in simulating the NF of a superhetreodyne receiver.

It is not strange at all.

weigiho wrote on May 4^th, 2009, 12:14pm:

My RF=1.021GHz, LO1=1GHz, IF1=21GHz, LO2=20GHz, and baseband=1MHz.

These are typos ?
Correctly they are IF1=21MHz and LO2=20MHz. Right ?

Show me netlist for "PORT0". Do you set type of "PORT0" as "dc" or "sine" ?
I think you do two tones large signal(LO1=1000MHz, LO2=20MHz) steady state analysis because your fundamental frequency of PSS is 20MHz.
Is this correct ?
�
Nodes, "Out+" and "Out-" are open loaded ?
If "Out+" and "Out-" are terminated by some resistor, turn off noise of them by setting temperature -273.15degC.

weigiho wrote on May 4^th, 2009, 12:14pm:

1.The way I applied the input is shown in the attached file.
I am not sure whether I should use egain=+/- 0.5 or +/-1 for RF input, but I use +/-1 anyway.

There are no difference about NF evaluation even if you choose egain=+/- 0.5 or +/-1.

weigiho wrote on May 4^th, 2009, 12:14pm:

2.The input of the mixer is not matched to 50 ohm.
3.The output of the mixer is not matched to 50 ohm.

You don't have to care about these at all.
http://www.designers-guide.org/Forum/YaBB.pl?num=1237656418

weigiho wrote on May 4^th, 2009, 12:14pm:

4.When I use results-->direct plot-->mainform-->......to plot the NF,
it shows NF=13.34dB at 1MHz.

This NF value is conventional SSB NF.

weigiho wrote on May 4^th, 2009, 12:14pm:

5.When I use results-->print-->noise summary, I got something in the following
Device � �Param � �Noise Contribution � �% Of Total
/PORT0 rn 2.39115e-10 21.84
/N8 � � id 1.38898e-10 12.69
/N4 � � id � � � 1.38898e-10 12.69
Spot Noise Summary (in V^2/Hz) at 1M Hz Sorted By Noise Contributors
I calculate the NF=10*log(1/0.2184)=6.6075dB. Is this right?

Right.
But this NF value is DSB NF of Agilent ADS's definition, which is called as ASB_NF(All SideBand NF) to distinguish it from conventional DSB NF.

See http://www.designers-guide.org/Forum/YaBB.pl?num=1162399761

Agilent Simulators such as ADSsim and GoldenGate give following three NF.
� � - SSB_NF(Conventional SSB NF)
� � - DSB_NF(Conventional DSB NF)
� � - ASB_NF(All SideBand NF, DSB NF of Agilent ADS's definition)

Actual NF meter such as Agilent N8975A Noise Figure Analyzer gives ASB_NF, neither SSB_NF nor DSB_NF.

weigiho wrote on May 4^th, 2009, 12:14pm:

Why these 2 results are different?

This is because there are many spurious receiving frequencies in your RX System.

LO1=1000MHz, IF1=21MHz, LO2=20MHz, IF2=1MHz
At least, there are following remarkable spurious receiving frequencies in your RX System.
� (1) Primary Image Frequency for IF1 ; 979MHz
� (2) Primary Image Frequency for IF2 ; 981MHz and 1019MHz
� (3) Half IF Image Frequency for IF1 ; 989.5MHz and 1010.5MHz
� (4) Half IF Image Frequency for IF2 ; 990.5MHz and 1009.5MHz

If your spurious receiving frequencies in your RX System are only (1) and (2), SSB_NF-ASB_NF is lesser than 6dB.
But if there are many receiving frequencies in your RX System other than (1) and (2), SSB_NF-ASB_NF could be larger than 6dB like your case.
In your case, SSB_NF=13.34dB, ASB_NF=6.607dB, SSB_NF-ASB_NF=6.733dB>6dB

Confirm your spurious receiving frequencies by using PSS/PXF or QPSS/QPXF and show me results.

weigiho wrote on May 4^th, 2009, 12:14pm:

should I correctly give the input to the superhytereodyne receiver?

See my appends in http://www.designers-guide.org/Forum/YaBB.pl?num=1208883935

weigiho wrote on May 4^th, 2009, 12:14pm:

Is the egain=1 correct?

Correct. Any value except for 0 is OK.

weigiho wrote on May 4^th, 2009, 12:14pm:

Do I have to put 2 seperate ports as input?

No, you don't have to do.

weigiho wrote on May 4^th, 2009, 12:14pm:

Does input/output matching matter?

No, it doesn't matter.

weigiho wrote on May 4^th, 2009, 12:14pm:

I really have no idea. Can you kindly help me with this?

I'm not kind and patient enough for explaining such too basic issues.
If you can not still understand, other people who is very kind and patient will help you.

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« Last Edit: May 5^th, 2009, 8:41am by pancho_hideboo »

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weigiho

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Re: Questions about Mixer NF simulation.
Reply #5 - May 5^th, 2009, 12:35pm

pancho_hideboo wrote on May 4^th, 2009, 11:43pm:

You are appending completely new questions without responding to the following.
http://www.designers-guide.org/Forum/YaBB.pl?num=1239925339/1#1

From contents of this new questions, you should append this new questions to the following your another post.
http://www.designers-guide.org/Forum/YaBB.pl?num=1239389950

weigiho wrote on May 4^th, 2009, 12:14pm:

Actually I found something strange in simulating the NF of a superhetreodyne receiver.

It is not strange at all.

weigiho wrote on May 4^th, 2009, 12:14pm:

My RF=1.021GHz, LO1=1GHz, IF1=21GHz, LO2=20GHz, and baseband=1MHz.

These are typos ?
Correctly they are IF1=21MHz and LO2=20MHz. Right ?
Yes. Thanks for your correction.

Show me netlist for "PORT0". Do you set type of "PORT0" as "dc" or "sine" ?
PORT0 (net0181 0) port r=50 type=dc ampl=1u freq=1.021G fundname="F1" \
fundname2="F2"
I set it to dc.

I think you do two tones large signal(LO1=1000MHz, LO2=20MHz) steady state analysis because your fundamental frequency of PSS is 20MHz.
Is this correct ?
Yes. You are right!

Nodes, "Out+" and "Out-" are open loaded ?
If "Out+" and "Out-" are terminated by some resistor, turn off noise of them by setting temperature -273.15degC.
They are opened.

weigiho wrote on May 4^th, 2009, 12:14pm:

1.The way I applied the input is shown in the attached file.
I am not sure whether I should use egain=+/- 0.5 or +/-1 for RF input, but I use +/-1 anyway.

There are no difference about NF evaluation even if you choose egain=+/- 0.5 or +/-1.

When I try +/-0.5, I got SSB_NF=18.59dB, the ASB_NF=10*log(1/0.0653)=11.82dB at 1MHz. Both are different from using +/-1. It seems to me that it matters.

weigiho wrote on May 4^th, 2009, 12:14pm:

2.The input of the mixer is not matched to 50 ohm.
3.The output of the mixer is not matched to 50 ohm.

You don't have to care about these at all.
http://www.designers-guide.org/Forum/YaBB.pl?num=1237656418

weigiho wrote on May 4^th, 2009, 12:14pm:

4.When I use results-->direct plot-->mainform-->......to plot the NF,
it shows NF=13.34dB at 1MHz.

This NF value is conventional SSB NF.

weigiho wrote on May 4^th, 2009, 12:14pm:

5.When I use results-->print-->noise summary, I got something in the following
Device Param Noise Contribution % Of Total
/PORT0 rn 2.39115e-10 21.84
/N8 id 1.38898e-10 12.69
/N4 id 1.38898e-10 12.69
Spot Noise Summary (in V^2/Hz) at 1M Hz Sorted By Noise Contributors
I calculate the NF=10*log(1/0.2184)=6.6075dB. Is this right?

Right.
But this NF value is DSB NF of Agilent ADS's definition, which is called as ASB_NF(All SideBand NF) to distinguish it from conventional DSB NF.

See http://www.designers-guide.org/Forum/YaBB.pl?num=1162399761

Agilent Simulators such as ADSsim and GoldenGate give following three NF.
- SSB_NF(Conventional SSB NF)
- DSB_NF(Conventional DSB NF)
- ASB_NF(All SideBand NF, DSB NF of Agilent ADS's definition)

Actual NF meter such as Agilent N8975A Noise Figure Analyzer gives ASB_NF, neither SSB_NF nor DSB_NF.

weigiho wrote on May 4^th, 2009, 12:14pm:

Why these 2 results are different?

This is because there are many spurious receiving frequencies in your RX System.

LO1=1000MHz, IF1=21MHz, LO2=20MHz, IF2=1MHz
At least, there are following remarkable spurious receiving frequencies in your RX System.
(1) Primary Image Frequency for IF1 ; 979MHz
(2) Primary Image Frequency for IF2 ; 981MHz and 1019MHz
(3) Half IF Image Frequency for IF1 ; 989.5MHz and 1010.5MHz
(4) Half IF Image Frequency for IF2 ; 990.5MHz and 1009.5MHz

If your spurious receiving frequencies in your RX System are only (1) and (2), SSB_NF-ASB_NF is lesser than 6dB.
But if there are many receiving frequencies in your RX System other than (1) and (2), SSB_NF-ASB_NF could be larger than 6dB like your case.
In your case, SSB_NF=13.34dB, ASB_NF=6.607dB, SSB_NF-ASB_NF=6.733dB>6dB

Confirm your spurious receiving frequencies by using PSS/PXF or QPSS/QPXF and show me results.
I will check it. Thanks.

weigiho wrote on May 4^th, 2009, 12:14pm:

should I correctly give the input to the superhytereodyne receiver?

See my appends in http://www.designers-guide.org/Forum/YaBB.pl?num=1208883935

weigiho wrote on May 4^th, 2009, 12:14pm:

Is the egain=1 correct?

Correct. Any value except for 0 is OK.

weigiho wrote on May 4^th, 2009, 12:14pm:

Do I have to put 2 seperate ports as input?

No, you don't have to do.

weigiho wrote on May 4^th, 2009, 12:14pm:

Does input/output matching matter?

No, it doesn't matter.

weigiho wrote on May 4^th, 2009, 12:14pm:

I really have no idea. Can you kindly help me with this?

I'm not kind and patient enough for explaining such too basic issues.
If you can not still understand, other people who is very kind and patient will help you.

Thanks very much! You already help me a lot!

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pancho_hideboo

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Re: Questions about Mixer NF simulation.
Reply #6 - May 5^th, 2009, 7:55pm

weigiho wrote on May 5^th, 2009, 12:35pm:

weigiho wrote on May 4^th, 2009, 12:14pm:

1.The way I applied the input is shown in the attached file.
� �I am not sure whether I should use egain=+/- 0.5 or +/-1 for RF input, but I use +/-1 anyway.

pancho_hideboo wrote on May 4^th, 2009, 11:43pm:

There are no difference about NF evaluation even if you choose egain=+/- 0.5 or +/-1.

When I try +/-0.5, I got SSB_NF=18.59dB, the ASB_NF=10*log(1/0.0653)=11.82dB at 1MHz.
Both are different from using +/-1. It seems to me that it matters.

Sorry, my answer was not appropriate.

egain=+/-1.0 ; SSB_NF=13.34dB, ASB_NF= �6.607dB=SSB_NF-6.733dB
egain=+/-0.5 ; SSB_NF=18.59dB, ASB_NF=11.851dB=SSB_NF-6.739dB

NF is calculated like following.
NF=1+Na/(Gain²*Nin)
here Na=Square of intrinsic output voltage noise from DUT [Vrms²/Hz],
Nin=Square of input voltage noise from source(=4*k*T*Rs) [Vrms²/Hz],
Gain=Voltage Conversion Gain which is the sum of sidebands you have interests in.

So in your case, Gain of "egain=+/-1.0" is twice compared to "egain=+/-0.5".

What value you should use for "egain" is dependent on your usage of NF.
If you use NF for level diagram study for various block cascades, you can't use your NF directly.
You can't apply your NF in common standard Friis's equation for cascaded NF.

You can use your NF for relative comparison between your DUT's Noise performances.
In this purpose, NF value is relative, so there are no difference about NF evaluation even if you choose egain=+/-0.5 or +/-1.

I don't use your method for driving inputs. �
Especially I never use VCVS for input drive because impedances seeing from DUT are completely zero.
See the following.
http://www.designers-guide.org/Forum/YaBB.pl?num=1231854969/5#5
http://www.designers-guide.org/Forum/YaBB.pl?num=1233236788

weigiho wrote on May 4^th, 2009, 12:14pm:

2.The input of the mixer is not matched to 50 ohm.
3.The output of the mixer is not matched to 50 ohm.

pancho_hideboo wrote on May 4^th, 2009, 11:43pm:

You don't have to care about these at all.
http://www.designers-guide.org/Forum/YaBB.pl?num=1237656418

There is optimal source impedance for NF.
So if an input matching is changed, NF is also affected.

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« Last Edit: May 6^th, 2009, 10:53am by pancho_hideboo »

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pancho_hideboo

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Re: Questions about Mixer NF simulation.
Reply #7 - May 11^th, 2009, 6:49am

The following was not correct.
pancho_hideboo wrote on May 5^th, 2009, 7:55pm:

NF is calculated like following.
NF=1+Na/(Gain²*Nin)
here Na=Square of intrinsic output voltage noise from DUT [Vrms²/Hz],
Nin=Square of input voltage noise from source(=4*k*T*Rs) [Vrms²/Hz],
Gain=Voltage Conversion Gain which is the sum of sidebands you have interests in.

This equation is true only for ASB_NF.

More Generally, this has to be like following.
� � NF=Nout/(Gain²*Nin)
� � here Nout=Square of output voltage noise [Vrms²/Hz],
Nin=Square of input voltage noise from source(=4*k*T*Rs) [Vrms²/Hz],
Gain=Voltage Conversion Gain which is the sum of sidebands you have interests in.

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