LMX2820EVM: Phase Noise

Prodigy 90 points

Replies: 13

Views: 155

Part Number: LMX2820EVM

A phase noise of LMX2820EVM is bad.

Result of a measurement is far apart from simulation.

Please give me advice to become same as a simulation result.

13 Replies

  • Hello,

    Give us some time to look into these settings you have made and we will get back to you shortly.

    Regards,

    Aaron

    For more information on TI Clocking and Timing tools and training please see below links:

  • In reply to Aaron Black:

    Hi There,

    Can you provide a phase noise plot of your OCXO?

  • In reply to Noel Fung:

    Hello,

    Thank you for your reply.

    I submit measurement data of OCXO.

    Regards,

    Arai

  • In reply to user4852208:

    Hi Arai-san,

    Your OCXO phase noise is very good, hope the spurs are not real and is just a measurement issue.

    Given this good phase noise, I don't know why the phase noise of LMX2820 is bad. 

    Were you using the "EVM default mode" setting but just change the output frequency to 1.7GHz?

    Could you also try other reference clock? For example, signal generator? You could try with 800MHz reference clock and then set Pre-R = 4 to get the same 200MHz fpd. 

  • In reply to Noel Fung:

    Hi Noel-san,

    I set it and measure in the "EVM default mode".

    When fout=6GHz(RFOUTAN)

    When REF IN = + 10 dBm

    I seemed to improve some results, but the result still has a problem.

    Other REF input is difficult, want to wait.

    A phase noise has difficult good signal source.

  • In reply to user4852208:

    The second photograph is a mistake.

  • In reply to user4852208:

    I show addition data.

    REF=1GHz OCXO, fpd=200MHz(Pre-R=5),


    Please give me advice.

  • In reply to user4852208:

    Hi Arai-san,

    When did you order this EVM? What is the part number as shown in the top marking of the device? Is it LMX or PLMX?

    The noise bump between 10kHz and 100kHz could be reduced by increasing the bypassing capacitor at pin 3. Change this capacitor to 4.7µF or larger.

    Higher input frequency or input power improves phase noise suggests that the slew rate of the reference clock is also important. If possible, use a square wave reference clock. Also try use a sma connector (aka I-join) instead of sma cable to connect the OCXO and EVM together.

  • In reply to Noel Fung:

    Hi Noel-san,

    >When did you order this EVM? What is the part number as shown in the top marking of the device? Is it LMX or PLMX?

    1. It is "LMX"

        order number : T01091457

    > The noise bump between 10kHz and 100kHz could be reduced by increasing the bypassing capacitor at pin 3. Change this capacitor to 4.7µF or larger.

    2. I will try this after.

    > Higher input frequency or input power improves phase noise suggests that the slew rate of the reference clock is also important. If possible, use a square wave reference clock.

    > Also try use a sma connector (aka I-join) instead of sma cable to connect the OCXO and EVM together.

    3. Square wave reference clock is difficult.

       Is "I-join" connected by SMA-M to SMA-M.

       the OCXO and EVM because SMA-Female.

  • In reply to user4852208:

    Hi Arai-san,

    You've got the latest silicon, your EVM is fine.

    Yes, use male sma i-join like the picture in below.