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CC1125: Custom board designed for 915MHz could be used for 920MHz in Japan?

luis.lopez
Expert 1050 points
Part Number: CC1125
Other Parts Discussed in Thread: CC1190, , CC1120, CC1200

Hello!

We have developed a custom board with CC1125+CC1190, following your tips and your examples (many thanks TI), which works perfectly in the range of 915MHz (it is certified for Americas).

Now, we have received a proposal to use that board on Japan, but studying the range of ISM bands on Japan I see that we need to work on range 920 MHZ and upper (and re-certified it).

Could we use the same board without changes on the components? Or is it necessary to change components as the same as the change from 868 to 915MHZ? Even, in the worst case, is it necessary to change the design?

Many thanks in advance!

BR,

Luis

  • 0
    TI__Guru**** 317180 points

    If I'm not mistaken the requirement for T-108 is -30 dBm both for 2. and 3. harmonic. This is the same as for ETSI. The CC1120 + CC1190 ref design for 869.5 MHz have two notches to attenuate the 2. harmonic sufficient. Since you want to operate in some of the channels in the 920 band you probably have to move the notches some to attenuate the 2. harmonic of this new frequency. The rest of the passives don't need to be changed. 

    For the SAW filter: Since the maximum output power is 24 dBm in this band it could be that the SAW filter is not required. Use a placeholder for a SAW filter but test first without to see if it's sufficient. 

  • 0
    Expert 1050 points

    Many thanks for your quick response, TER

    I am afraid that my english is not too good for understand some words. What do you refer with the "two notches"? 

    I have been reading your document "AN126 - Using the CC1200 Under ARIB STD T108" and viewing the schematic CC1200EM 920, I see that it is very similar to the schematic of CC112x+CC1190 , changing some values of capacitors and inductors, and, of course, the use of the front end CC1190.

    So changing (moving) the notches and viewing how the SAW filter acts on the TX/RX, could I use the same design?

    Thanks again for your help, TER

  • +1 in reply to luis.lopez
    TI__Guru**** 317180 points

    "AN126 - Using the CC1200 Under ARIB STD T108" only outline the performance with some different CC1200 designs. This is not relevant in your case since the performance is set by the CC1190 part. 

    You should start from this: https://www.ti.com/lit/pdf/tidr235 but you need to adjust the values of the components in red boxes to the band you want to operate in:

  • 0 in reply to TER
    Expert 1050 points

    For 915MHz, the components remarked on red boxes are not mounted. Forgive me for taking advantage of your knowledge, TER, but do you think I could still keep it that way for the 920MHZ?

    I must recognized you that I don't have the radiofrequency knowledge and the tools to recalculate the radio circuit. Really, I take your designs and follow all your recommendations in our all radio designs.

  • 0 in reply to luis.lopez
    TI__Guru**** 317180 points

    If you want to operate according to T-108 you have to be able to recalculate and do a number of tests to tune and verify the design. 

  • 0 in reply to TER
    Expert 1050 points

    OK, I understand it.

    Thank you, TER.