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AFE7444EVM: Signal Levels

SM
Expert 1750 points

Part Number: AFE7444EVM

Hello,

    What is the maximum signal level that can be fed to the AFE7444 EVM and the maximum signal level at the output of the EVM?

As per the datasheet for maximum attenuation setting of the DSA (20 to 28dB) the input level can be 12.4dBm. Does the DSA's IP3 level have an impact on the ADC's performance? The various plots show the IMD and IP3 measurements for -3dBFS and DSA = 4dB. What is the absolute signal level here?

We are downconverting a 12GHz signal having a bandwidth of 500MHz to a lower frequency (2-4GHz) for our application to be subsequently sampled  by the AFE7444. Is there any guideline to choose the IF considering our signal bandwidth (planning to sample it at 3GSps). 

Thank you for your help in advance,

  • 0
    TI__Mastermind 18095 points

    SM:

    Per the datasheet, the maximum full scale input with no DSA attenuation is -7.6 dBm.  The maximum with full DSA attenuation is +12.4 dBm.  The TX output power maximum is dependent on output frequency.  You can see the plot in figure 119.  The output power varies from ~5 dBm to -5 dBm over 500 MHz to 6 GHz.

    The first 8 dB of RX attenuation range is digital, so it does not have an impact on IMD performance as a typical analog attenuation would have.  After that initial 8 dB, the attenuation is analog and the IMD product drops (ideally) 3-to-1 with respect to attenuation setting.  The absolute signal is still the same as above: -7.6 dBm.  If dealing with 2-tone or modulated signals, keep in mind the total average power and PAR of the signal.

    For your application, keep in mind a couple of frequency planning considerations.  If sampling at 3 GSPS, the Nyquist boundaries will be at 1.5 GHz and 3 GHz.  You will not be able to effectively capture signals near or at the boundaries without modifying the sampling rate.  Also be aware of the interleaving spurs and their locations.  The datasheet outlines a variety of combinations of interleaving spur frequency locations (relative to sampling rate and input frequency) and spur level.  Sometimes for large BW applications these spurs can fall into your desired band.

    --RJH