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IIP3s are different on left and right side of LO frequency

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bageduke

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We have tested out chip, but found out that IIP3 value measured on + side is much lower than - side.

I couldn't figure out what cause this. From mathematical view, they should be same. Can anyone explain this phenomenon to me?

Thanks,
 

Re: IIP3s are different on left and right side of LO frequen

If an amplifier gets imbalance between IMD products, the amplifier exhibits so named “memory effect”, which is cause by a lag between AM-AM and AM-PM characteristics.
Generally this is due to a poor bias decoupling at low frequencies causing a distortion of the envelope currents which result in IMD asymmetry.
 
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Re: IIP3s are different on left and right side of LO frequen

vfone said:
If an amplifier gets imbalance between IMD products, the amplifier exhibits so named “memory effect”, which is cause by a lag between AM-AM and AM-PM characteristics.
Generally this is due to a poor bias decoupling at low frequencies causing a distortion of the envelope currents which result in IMD asymmetry.
Click to expand...

Thanks, vfone,

Can you explain it a little bit more, or do you have some paper regarding this issue. I am so glad that you know the answer of this.

Thanks a lot.
 

Re: IIP3s are different on left and right side of LO frequen

Just wondering if you tested this at many frequencies across the AMP's Bandwidth.
You might be on the edge of a filter for example...
 

Re: IIP3s are different on left and right side of LO frequen

Element_115 said:
Just wondering if you tested this at many frequencies across the AMP's Bandwidth.
You might be on the edge of a filter for example...
Click to expand...

Yes, I tested it across the whole band - actually, the receiver is designed for wide band - it exhibits the same behavior, but the differences between left side and right side are different across the band.
 

hi, now I encounter the same problem. Anyone can tell me how to get the proper IIP3 values according to the measured results with the imbalance between IMD products? Thanks a lot!!!
 

Thanks for tony_lth! But is there any reason to select the worse IM3? Say, Why not select the average value of the two IM3?
 

Such as for PA IM3, the spectrum from PA must meet the requirement of MASK. The worse IM3 maybe break the MASK, but the better one maybe not. At this situation, the left spectrum and the right one can't be averaged. So the IM3 should select the worse one.
 
OK, I catch you. Thank you, tony!
 

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