• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 19 subscribers
  • Views 1018 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.

Practical question about size of matching components

kazola
Guru 18595 points

Hi fellows,

I'm losing my eyes while soldering manually all these 0402 (metric size) components they use in the TI Antenna DK.

However, while they present lower parasitics, maybe we could be ok with 0603, or even 0805 size :) Also, our manufacturer ask for bigger sizes.

So, my question is:

  1. Should I insist in 0402 sizes?
  2. Is there any paper analyzing antenna range differences depending on the sizes of the matching networks? Please say so! :)
  3. Could you indicate me which brand of capacitors and inductors you usually use? I have GRM* and GJM* capacitors from Murata  and LQG* Inductors from Murata and also 0603HP* Inductors from Coilcraft. Am I ok with these ones? :)

I'm just starting in these topics so please be patient! :) Have a nice day!

  • 0
    TI__Mastermind 21280 points

    Hi Kazola,

    0603 should also work but the final values might be slightly different from the reference design due to parasitics. Components from any manufacturer should be fine however we use GRM and LQG series.

    Antenna range depends on many other factors, however regarding components, it is important that the matching circuit provides an acceptable VSWR into the antenna. This circuit can be optimized by test and measurement with any components and size.

    FI

  • 0
    TI__Mastermind 27145 points

    Hi,

    We always recommend to copy our reference designs. Yes, you are right, the smaller size comopnnets offer lower parasitics.

    You  need to look into the Self Resonant Frequecy (SRF) of the components. SRF changes with the size of the component also.

    If you need to use bigger size components then you need to optimize the matching circuit.

    Yes, we use GRM series in our reference design. LQW series is better for Matching and filter circuits.

    LQG can be used at PS filtering and low frequency filters. Plase observe for SRF of components.

    Thanks,

    PM

  • 0 in reply to PM
    Guru 18595 points

    Hi!

    Many thanks for your answers! :)

    I understand all your points.

    So, I will switch from LQG to LQW, since they have higher SRF. However, there is still something I do not get.

    A Murata LQW18AN10NJ00* inductor, 0603 in size, has a Q of 35.

    A Murata LQW15AN10NJ00* inductor, 0402 in size, has a Q of 31.

    Both have same SRF 6 GHz.

    Theoretically, 0402 should have less parasitics.

    So, how do you explain this?

    :)

    Have a nice day! After you clarifying this to me, I will highlight all this as solved :)

  • 0 in reply to kazola
    TI__Mastermind 18780 points

    If you are to match an antenna, in my opinion, you can use the LQG serie and get good performance. When we tune antennas, most often we use multilayer inductors as wire wound inductors are more expensive and the performance will be more or less the same. But in the matching and filtering network, you will gain both sensitivity and output power by using wire wound inductors, see more in DN017 http://www.ti.com/lit/an/swra168a/swra168a.pdf. Note that when tuning antennas, both the size of the ground plane and casing will affect the resonance of the antenna and must be taken into consideration when choosing matching components.  

  • 0 in reply to kazola
    TI__Guru**** 317180 points

    Actually for antenna matching multilayer inductors should be considered. With wire bound the matching will be high Q which will work well in a static environment but quite often S11 will change some dependent on if someone/ thing is close to the antenna and with a high Q match you risk to de-tune the antenna. With a low Q match the system will have higher tolerance for external changes.

  • 0 in reply to TER
    Guru 18595 points

    All this is very useful info.

    Thanks to all.

  • 0 in reply to kazola
    TI__Guru** 106705 points

    Just to add to CHS and TER's input above, for all our 2.4 GHz reference designs we stick to multilayer inductors throughout the RF match.

    Cheers,

    Fredrik