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LMX2592 output power optimization

JohnP
Intellectual 470 points

Other Parts Discussed in Thread: LMX2592

Dear Sir

Please can you also suggest how to maximise the output power of the LMX2592 over the 4.3 to 8.3GHz frequency range and explain the "(characteristic)" capacitance in section 8.1.6 in the data sheet? Is the "(characteristic)" capacitance the equivalent shunt parasitic capacitance of the chosen inductor? What is the output impedance of the RF outputs?

Do you recommend a specific inductor over this range, or could you recommend a balun to use both the true and complementary outputs and convert to single ended operation?

Thanks

JP

  • 0
    TI__Expert 4085 points

    Hi JP,

    Thank you for your interest in our products. We received your question and will be answering it as soon as possible. We appreciate your patience.

     Best regards,
    Julian

  • 0
    TI__Expert 8585 points

    Hi JP,

    By characteristic capacitance we mean the intrinsic capacitance of the part. The parasitic of the capacitance can have additional effects. Following the equation in 8.1.6 should get you close in the peak output power at your intended frequency. for your range of 4.3 to 8.3GHz I would design for around the high end 8GHz (so an inductor like 280pH). Ideally, a balan can increase the power through the combination, but that is also dependent on the performance of the part selected.

    Regards,

    Brian Wang

  • 0 in reply to Brian Wang
    Intellectual 470 points

    Hi Brian

    Thanks for the information. When you say 'intrinsic capacitance of the part' I assume you mean the intrinsic capacitance of the LMX2592? When you say 'parasitic of the capacitance' I assume you mean the 'parasitic of the inductance'?

    Can you recommend an inductor?

    Can you recommend a balun?

    Thanks

    John

  • 0 in reply to JohnP
    TI__Expert 8585 points

    John,

    Correct, intrinsic is for the LMX2592 itself, and then parasitic for the external inductor (mainly need to take into account the inductors specs at the frequencies you need)

    Inductor, take a look at Murata's LQP02TN0N3C02:

    Balun, I found one from Marki Microwave the BAL-0010, but with the 8dB or so insertion loss at 8GHz, you wont be getting the desired gain from combining the two differential traces. Better to use one end and terminate the other for max power.

  • 0 in reply to Brian Wang
    Intellectual 470 points

    Thanks , that's really helpful.

    John