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Question about EVM test result and common mode level for ADL5375

Question asked by Matt1012 on Aug 10, 2016
Latest reply on Sep 20, 2016 by Matt1012

Hi, 

I have done EVM measurement of ADL5375 based on 64QAM modulation. LO is set to 3GHz.

Attachment includes the results of the two scenarios.

a) AWG (no offset applied)  supplies differential IQ with 10M symbol rate, EVM=2.27%

b) AWG supplies differential IQ with 10M symbol rate and with common mode offset so that the measured Vcm@ baseband input pin=0.5V.   EVM=10.7%

Would like to know your advise about the result.

 

As datasheet  indicates Varying the baseband common-mode voltage influences the current in the mixer and affects overall modulator performance. The recommended dc voltage for the baseband common-mode voltage is 500 mV dc for the ADL5375-05.

 

 

Any suggestion?

 

Thanks.

Matt.

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