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AFE7071: qmc

Part Number: AFE7071

Hello!!!

MY question is about the QMC of AFE7071,there are three parameters to adjust the siginal:phase,I_offset/Q_offset and gainI/gainQ.however ,when i configure one of the three parameres ,which one matters more?

 what is the relationship among them?even how to design the parameters?

 Thank you all very much with help!!!!!

  • Hi Ljj Jason,

    We are taking a look into your question, and will be back with you soon.

    Best Regards,

    Dan
  • hello dBrock,

    can i have your number?or even how can i contact with you?  

  • Hi Ljj Jason,

    My apologies for the delay.

    Each of these parameters are important for balancing the I and Q signals. I/Q imbalance can happen in the analog portions of the DAC, and can cause sideband images.

    Please see section 2 and 3 of this document for a more in depth explanation of the effects of I/Q imbalance. While it focuses on use of an ADC, the theory is sound for DACs as well.

    www.ti.com/.../slwu085.pdf

    Best Regards,

    Dan
  • Hi Dan ,
    thank you all the same!
    the LO freethrough is well done within your help .however,i cannot adjust and cancell the DC offset(sideband image),there are huge amount of parameters combination ,even if i increased the factor of the phase by 20(range of 1024) while the other parameters are settled,as well as adjuesting the Gaina and Gainb(range of 2048),it is really troubled me .
    could you please help ??
    looking forward your help
    thank you a lot
  • Hi Ljj Jason,

    Are you using the AFE7071EVM evaluation module? When you change these QMC parameters, do you notice any change (do they appear to be functioning)?

    Are you enabling the QMC and offset first?

    It would be helpful if you could share your register configuration and any other setup information.

    Best Regards,

    Dan

  • Hi Dan,

    I didnot use the AFE7071EVM .I had enabled the QMC、offset first and there is  little change functioned with the sideband image,before adjusting the imbalance,I 

    have chosen the better filter_tune.even more i have had my hardware environment examined.so,that is really incredible.

    THANKS!!!

  • Hi,Dan

    the register 0x05,I configured as CA, the detail reigsters are configured as follows:

    00-B2

    01-90

    02-00

    03-DC

    04-0F

    05-CA

    06-00

    07-13

    0B-06

    09-00

    0A-FE

    08-FF

    0F-64

    0E-FF

    0D-00

    0C-00

    I have adjusted the baseband of the filter to 1 MHz,the side suppresion and LO feedthrough cannot be bucked to what really I expected even i have adjusted the better register-configuration.that is really troubled  me .Looking forward your careful help.

    THANKS!!!

    Ljj Jason

  • Hi Ljj Jason,

    Could you please provide the DAC pattern file that you are using and other setup parameters (clock frequency, LO, etc..)? That will make it easier for me to replicate your issue on my setup. Any images that you can provide of the output, and what you find to be out of specification will also be helpful.

    Best Regards,

    Dan
  • Hi dBrock,

    I have almost adjusted the QMC done,it is the timing that matters a lot,eventually,the LO feedthrough even the images comes down within the help of my teammeat

    thank you all the same!!

    Best Regards,

    Jason Ljj

  • Hi Jason Ljj,

    I'm glad to hear that you are making progress. Unless you have further questions on this topic, I will close the thread.

    Best Regards,

    Dan

  • Hi Dan,

    That is no problem furthermore

    THANKS

    Jason  Ljj