• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 21 subscribers
  • Views 362 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LMX2492EVM: To achieve a large linear chirp (Chirp bandwidth of 2 GHz to 7 GHz)

ArTzy
Genius 15349 points
Part Number: LMX2492EVM
Other Parts Discussed in Thread: LMX2492, LMX2492-Q1, LMX2594, LMX2572,

Hi Experts,

Good day.

Customer is looking at LMX2492 EVM with LMX2492-Q1 chip. The application being targeted is FMCW LiDAR. They want to achieve a large linear chirp (Chirp bandwidth of 2 GHz to 7 GHz). Some of the forums shows that for such a large span, the VCO needs to be calibrated. The image shown in one of the datasheets shows a ramp from 7.5 GHz to 15 GHz with some glitches. It was mentioned that the glitches were an artifact from the measuring instrument. We want to know if the VCO calibration results in frequency jumps in between.


https://www.ti.com/lit/ds/symlink/lmx2594.pdf

If any other competing products with larger linear ramp are available, they can be added as an alternative.

Thank you.

Regards,
Archie A.

  • 0
    TI__Guru* 90880 points

    Hi Archie,

    For FMCW application, linear frequency ramp is needed so LMX2594 is not a suitable part as the VCO calibration will result in a staircase ramp instead of a linear ramp.

    The configurable pause time in below plot is reserved for VCO calibration. 

    Customer can use LMX2492 as long as they are able to find a VCO that could support 2G to 7GHz tuning range.

  • 0 in reply to Noel Fung
    TI__Genius 15349 points

    Hi Noel,

    Thank you for providing the details. Just got feedback from Cx:

    The evaluation board of LMX2492 EVM offered by Texas Instruments provides a tuning range of ~1. 4 GHz (9. 4GHz to 10.8 GHz). Is it feasible for you to integrate a VCO with a large tuning range on the evaluation module? Alternatively, can you suggest external VCOs which offer a tuning range of several GHz. I would also like to look at the document which mentions the configurable pause time between the VCO calibrations. The LMX 2492 EVM has a specification for tuning up to 14 GHz. Is this also achieved through multiple VCO calibration steps? Does the evaluation board have the LMX2492-Q1 (automotive grade with low phase noise) or the other chip (LMX2492 with poorer phase noise performance)?

    Regards,
    Archie A.

  • 0 in reply to ArTzy
    TI__Guru* 90880 points

    Hi Archie,

    At the moment, we have no plan to change the EVM.

    I don't have a suggestion for the GHz tuning range VCO, as far as I know, the choice is very limited. GHz tuning range VCO is not a common device. 

    Please check LMX2572 datasheet, I have more words on the description of the ramp function. LMX2572 uses the same ramp engine as LMX2594.

    LMX2492 is a PLL only device, there is no calibration engine for the VCO. 

    The LMX2492EVM has LMX2492 (industrial grade) device on board. Both the auto grade and industrial grade device has the same noise performance.