This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2592EVM: A and B output channel power difference

Part Number: LMX2592EVM
Other Parts Discussed in Thread: LMX2582EVM

Tool/software:

LMX2592EVM has two differential channels A and B. When I measure power level at 6.8 GHz, I get app. 6 dB lower power from channel B. For 1.2 GHz I don't see significant difference for both channels although there is a T type attanuator in channel B. Can you explain the reasoning? 
  • Hi There,

    The pull-up approach is different in output A and output B. 

    Output B use inductor pull up so as to get higher output power at higher frequency. 

    At 6.8GHz, I expect we should get more power from output B. I can take a look in the lab tomorrow.

  • Hi There,

    I use a socket board, which does not have the T-attenuator at output B.

    At 6.8GHz, outB power is 3.3dBm while outA power is -1.42dBm.

    At 1.2GHz, outB power is 7.66dBm while outA power is 0.38dBm.

    So your observation is correct, the 6dB "drop" at 6.8GHz is probably due to the T-attenuator. 

  • Hi Noel,

    Thank you for your answer.

    In the case of inductive pull-up for output B shouldn't we see higher power for 6.8 GHz? Is the  T-attenuator only difference in your socket board?

    I can share my measurement about comparing 1020 and 4080 MHz powers for both outputs using same power settings by TICspro.


    You see, as far I understood inductive pull-up provides more power for 1020 MHz so we don't see the effect of T-Att. On the other hand for 4080 MHz we see significant drop about 6-7 dB for output B. Is it reasonable?

    Thank you for your time in advance.

  • Hi There,

    I've more data. The LMX2582EVM has the 6dB pad on channel B. The socket EVM does not have that pad. 

    the result tells us the inductor boosts the power up at 1GHz but not much at 4GHz. 

    this is probably due to the inductor value is not optimum.