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LMX2595: Phase Noise

Om sai ram
Prodigy 40 points

Part Number: LMX2595
Other Parts Discussed in Thread: LMX2820

could you please help me to find out the solution.

Requirement

Frequency : 5 to 18GHz

Phase Noise @ 11GHz : -85dBc/Hz @ 100Hz,

                        -110dBc/Hz @ 10KHz

1. relation between reference clock Phase Noise and Output signal Phase Noise, i mean how it will impacts?

2. if give the reference clock from TI board (clock) to LMX2595 Eval board, the Phase Noise values will match with the datasheet values?

3. Phase Noise controlling factors, can we control through loop band width or any other?

 

Expecting answer for all the questions. hope i will get response soon.

  • 0
    TI__Guru** 121130 points

    Hi There,

    the 1/f noise of the LMX2595 at 11GHz is already -106dBc/Hz@10kHz offset, it cannot meet your requirement.

    Would you consider to use LMX2820? 1/f noise is -111dBc/Hz@10kHz offset. However, part-to-part variation and temperature may degrade the phase noise, not sure how much margin you can tolerate. In addition, to meet this requirement, your reference clock source should also be super clean, otherwise the phase noise at this offset may actually dominated by the reference clock.

    as i told you already, if you have a clock source with below characteristic, you can get the datasheet values from the eval board.

    The overall PLL phase noise depends on many factors, loop bandwidth, PLL configuration, reference clock are some of the examples.

    Feel free to visit our website for some video trainings.

    www.ti.com/.../ti-precision-labs-phase-lock-loop-fundamentals.html

  • 0 in reply to Noel Fung
    Prodigy 40 points

    can you please suggest us parameters to control the Phase Noise. how it will improve? we are not focusing on the numbers but we are excited to know.

  • 0 in reply to Om sai ram
    TI__Guru** 121130 points

    Hi There,

    at 10kHz offset, both PLL 1/f noise and reference clock are the main noise sources.

    1/f noise is determined by the PLL, you need to choice a PLL that meet your requirement.

    Same for the reference clock, you need to pick a clock that meet this requirement.