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aaron_do Senior Fellow Offline Posts: 1398	TX SNR Nov 20^th, 2007, 3:27am Hi, does anybody know what sort of SNR we can expect from the transmitter output? I was thinking it would be in excess of 50 dB... thanks, Aaron
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pancho_hideboo

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Re: TX SNR
Reply #1 - Nov 20^th, 2007, 6:54am

Hi.

What is your definition of SNR in TX ?

If you are thinking of non-modulated signal, SNR you should evaluate is C/N or C/N0.
Here you have to consider bandwidth or offset frequency.

For modulated signal, SNR you should see is ACPR.
And you have to see noise floor for out of band region.
This out of band noise floor level is important for CDMA system.
I make level diagram for TX which plot cascaded ACPR anf noise floor level,
here I need P1dB(IP3) and NF of each stages.
You are thinking of this out of band noise floor ?

Higher order harmonics, images of DAC, Local Leakage, etc. are treated as spurious.

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aaron_do

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Re: TX SNR
Reply #2 - Nov 21^st, 2007, 4:32am

Hi,

thanks for the reply. I was actually talking about the signal power to the channel thermal noise ratio. As far as i know it is not normally considered in design, and when I asked a colleague he said it would be only 9 dB for GSM and 18 dB for WCDMA. I assumed he was talking about the signal to thermal noise power, but i guess he meant ACPR. I think I need to do a little reading

thanks,
Aaron

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