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LMX2594EVM: Harmonic performances

TISL
Expert 4910 points

Part Number: LMX2594EVM

Dear Support,

My customer doesn't succeed to reach the datasheet performances with our EVM, for the H1, H2 and H3 parameters.

Could you give us the setting details we used for the characterizations in page 9 of our datasheet? Can we get similar results with the EVM?

Regards,

  • 0
    TI__Guru** 115080 points

    Hi There,

    The harmonic measurement was taken from another board, not the customer EVM. 

  • 0 in reply to Noel Fung
    TI__Expert 4910 points

    Hi Noel,

    And can we get the setting details we used for this characterization?

    How could we get similar results with the EVM?

    Regards,

  • 0 in reply to TISL
    TI__Guru** 115080 points

    Hi There,

    To measure the harmonic, we used TICS Pro Default Mode setting, but change the output frequency to 11GHz max. because our SpecAn is up to 26GHz only.

    I do not think there is way to tweak the customer EVM board for better harmonic.

    what is customer's target on harmonic? what did they get from the customer EVM?

  • 0 in reply to Noel Fung
    TI__Expert 4910 points

    Hi Noel,

    You will find the customer measurements below, with the configuration used in “TICS Pro”).

    They’ve used pull-up resistor and 100MHz single-ended as reference.

    The first three curves represent the power of the first harmonic (fundamental tone), second harmonic and third harmonic. The last figure shows the dBc of the second and third harmonic with respect to the fundamental tone in dBc.

    Could you help to improve these results?

    Are there any parameters we should take care of?

    Regards,

  • 0 in reply to TISL
    TI__Guru** 115080 points

    Hi there,

    What is the target harmonic level? What are the application frequencies?

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Dear all,

    I'm Gabriel, the customer. Actually, we don't have an specific harmonic level (the best performance that we can acheive). The thing is that reading the datasheet I didn't find this information. Well, you can find this information for two tones (8GHz and 11GHz I think). For example, for 8GHz, the datasheet sais that the level of the second harmonic is -20dBc while the level of the third harmonic is -50dBc.

    This is why I found these measurements a bit strange, because the measured H2 is -20dBc aprox. but the measured H3 is -25dBc aprox. And, at lower frequencies the H2 and H3 level are even worst.

    We'll use the full bandwith of the synthetiser.

    Thank you very much in advance.

    Gabriel

  • 0 in reply to Gabriel Galindo
    TI__Guru** 115080 points

    Hi Gabriel,

    I think what you've gotten from the EVM reflects the performance from the EVM. We used another board with very short output trace to measure the output power and harmonic. Obviously, the performance from these boards are different. 

    H3 at lower frequencies is higher because the signal waveform is square wave. 

    The chip does not do anything to reduce the harmonics, since you are using the full bandwidth of the part, you will have to implement some kind of tracking filter to tackle harmonic issues.