ADL5375-15 sideband suppression and other

Hi All,

One of my customers is using ADL5375-15 Quadrature Modulator for his prototype board.

High-Speed DAC generates analog I/Q signal and is fed to ADL5375-15 through reconstruction filter designed by him.

Attached file “SSB-compression” shows sideband suppression performance taken by him.

Frequency condition is f0=3GHz, I/Q input freq=27MHz, LO=3GHz.

  • (1)  He made gain and phase calibration at f0 frequency. After calibration, he made sideband suppression performance test as shown attached file. He would like to confirm with you about the suppression performance as around -50dB and -47dB at around f0-8.5MHz is reasonable one.
  • (2)  He also made frequency bandwidth test. For the test, he first bypass the reconstruction filter, it means DAC output is directly fed to ADL5375-15. The DAC works at 250MSPS data rate. The response curve is attached as QMOD-OUT file. It down around 3dB at f0+/- 24MHz. I think that one of reason is Sinx/x roll-off, however roll-off amount is too large. Is my understanding is correct? Do you have any other advice on this?

Thank you for your help.

Ricky

attachments.zip
  • 0
    •  Analog Employees 
    on Jan 30, 2015 1:02 AM

    Hello,


    Sideband suppression performance is a parameter of gain and phase imbalance between I and Q that are related to EVM performance in system level. By optimizing amplitude(gain) and phase more, then we can get better number on sideband suppression. However, around -50dB sideband suppression would be reasonable for that BB range and it would be enough for EVM at communication application. Please refer to below link.

    http://www.analog.com/static/imported-files/circuit_notes/CN0134.pdf

    For flatness over +/-24MHz signal band, there would be three factor mainly. Roll-off(sinx/x) from DAC, Baseband flatness of ADL5375-15, RF Flatness  over 48MHz at 3GHz on ADL5375-15. It would be around -0.53dB from DAC roll-off at 24MHz. Approximately around 0.1dB at 24MHz from Baseband of ADL5375-15(Refer to  Fig 64 in datasheet). Not much from RF Flatness (Refer to Figure 28 for RF flatness). So 3dB at +/-24MHz is big.  It might be good to check DAC output and then move to Modulator to narrow down the issue.

    Thanks.

    Tony

  • Hi THA-san,

    Thank you for your detailed explanation.

    I will talk to my customer based on your advice.

    Best Regards,

    Ricky

  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:53 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin