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LMX2820EVM: spurious near the carrier at 22.4 GHz

Matteo Ricci
Prodigy 240 points
Part Number: LMX2820EVM
Other Parts Discussed in Thread: LMX2820

Tool/software:

Hi team,

i'm using the evaluation board of the PLL LMX2820 to generate an output frequency of 22.4 GHz.

The reference clock is a sinewave 100 MHz (from en external OCXO at +12V) with power +6 dBm.

The PLL is programmed according to the immage attached

Near this carrier, there are many  spurious: see the attached file.

Can you help me understand the reason for the presence of these spurious?

Thank you in advance.

Best regards,

Matteo Ricci

  • 0
    TI__Guru** 111250 points

    Hi Matteo,

    This is an integer channel, the spurs are not fractional spurs.

    Spur #9 and #10 are symmetrical, they are the 200MHz fpd spurs.

    Other spurs are not symmetrical, they may be coming from external like power supply or environment.

    below is the plot I've got from an  eval board.

  • 0 in reply to Noel Fung
    Prodigy 240 points

    Hi Noel,

    thanks for the reply.

    I repeat the measurement: see the following image.

    The spurious frequencies were generated by the spectrum analyzer during the downconversion stage.

    Thank you for the support.

    Best Regards,

    Matteo