• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 22 subscribers
  • Views 204 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

LMX2572EVM: Desired RF generated even when Vtune is disconnected

LMX2572EVM: Ramp duration mis-behaviour

Vanshaj Kaistha
Prodigy 80 points

Part Number: LMX2572EVM
Other Parts Discussed in Thread: LMX2572

 

I have observed LMX2572 (named LC in attached picture).

There are two issues observed

  1. Bandwidth , start and stop frequency is not same across observations, and
  2. Observed ramp duration is not same.

 

Ramp duration mis-behaviour can be overlooked, but how to assure the spectral purity?

 

image001.png

  • 0
    TI__Guru** 121000 points

    Hi There,

    925M to 960MHz are the output frequencies, the VCO frequency are 4x of the output frequencies. So the VCO ramp range is 140MHz. There will be two VCO calibration because your Threshold is 50MHz.

  • 0 in reply to Noel Fung
    Prodigy 80 points



    Thanks for your reply, but the real concern is the measured start and stop frequency.
    Kindly look the attached picture for Conf(configured value) & Measured (Measured value on spectrum analyser)
    e.g. Configured start freq is 925 MHz & stop freq is 960 MHz and the mesured start and stop freq is 922 and 960 Mz for ramp duration = 650uS

  • 0 in reply to Vanshaj Kaistha
    TI__Guru** 121000 points

    Hi There,

    Do you have a test equipment capable of measuring frequency vs time? A freq vs time plot can definitely help you understand what is going on.

    For example, if you are doing sawtooth ramp, then the frequencies drift could be due to overshoot.

    it could also be due to calibration.