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Original question:

LMX2594EVM: Reference PRO

LMX2594EVM: 100 MHz source - crystal or Ref Pro?

Keith clark
Prodigy 130 points

Part Number: LMX2594EVM
Other Parts Discussed in Thread: LMX2594,

Hi,

I have an LMX2594EVM board with Reference Pro interface and am trying to get the best possible phase noise performance from the LMX2594 at 8.2 GHz for a phase noise sensitive application. The LMX2594EVM can be supplied with a source either from a 100 MHz on board oscillator or via the Reference Pro board. I assumed that I would get better performance when using the Reference Pro board however, when I look at the phase noise performance the on-board crystal gives ~10dB better performance beyond ~20kHz, is this correct or have I a configuration problem somewhere?  I note that the datasheet says that for best performance the LMX2594 needs a VERY good source for optimum performance.

Many thanks for your help

Best regards

Keith

  • 0
    TI__Genius 12705 points

    Hello Keith,

     I would suspect a configuration issue or perhaps some loss in the connection from the reference pro to the LMX2594 input.

    The on board oscillator does give slightly better performance, but this is typically in range < 20kHz and no where near 10dB difference. 

    Usually we would see this type of issue  when someone tries testing with a low quality signal generator to drive the reference input.

    The noisy reference input then tends to dominate the phase noise profile and obscure the excellent phase noise of the LMX2594.

    Regards,