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Original question:

CC1101/CC1190 combo - CS detection happening during out-of-band interference

CC430F5137: EN 301 489 - EMC Radiated Immunity Phenomenon

ali sakir
Prodigy 20 points
Part Number: CC430F5137

Hello,

We are about to certify our products that are uses CC430F5137. When 3V/m electric field at frequency of 325.389617 MHz exposed to EUT(equipment under test), EUT stops transmitting.

Detailed radio parameters are shown below. Do you have any recommendation about how to overcome this issue?

RF front end is designed based on application circuit in figure 7.2 of CC430F5137 datasheet.Schematic view depicted below.

We retested the EUT according to narrow band response chapter of EN 301 489.

1-  3V/m electric field applied at 325.389617 MHz, EUT stoped transmitting.

2-  3V/m electric field applied at 325.489617 MHz, EUT transmited without any performance degradetation.

3- 3V/m electric field applied at 325.689617 MHz, EUT transmited without any performance degradetation.

4- 3V/m electric field applied at 325.689617 MHz, EUT transmited without any performance degradetation.

5- 3V/m electric field applied at 325.289617 MHz, EUT transmited without any performance degradetation.

6- 3V/m electric field applied at 325.189617 MHz, EUT transmited without any performance degradetation.

7- 3V/m electric field applied at 325.089617 MHz, EUT transmited without any performance degradetation

From now we are about to disregard that frequency. Still, we should declare IF filter frequency or operating bandwith.

How could we clarify the IF filter bandwidth ?

How should we calculate operating bandwidth?

Thanks in advance,

Ali

  • 0
    Prodigy 20 points

    Pictures:

    Radio Parameters

    Schematic View of EUT RF Front End

    EN 301-489 Clause 4.4 Narrow band response of receiver

  • 0 in reply to ali sakir
    TI__Mastermind 20870 points

    Hi,

    A team member will look into this and get back as soon as possible.

    Thanks.

  • 0 in reply to FI
    TI__Mastermind 27145 points

    Hi,

    Rx Filter BW required = (2* Deviation ) + Symbol Rate + 4* Freq Tolerance  (Crystal ppm)

    In your case:

    Dev = 50.780 KHz

    Data Rate: 55.540 KBPS

    Operating Freq = 433.161 MHz

    Crystal Tolerance  = 20 ppm (Presumed)

    Rx Filter BW Reqd = (2* 50.780) + 55.540 +( (4*20*433.161)/1000) = 191.7529 KHz.

    You may set the Rx Filter BW to 203.125 KHz ( the nearest setting). You can declare this as a operating filter BW.

    We recommend to use SmartRF Studio to generate the Register settings for your RF parameters ( Data rate, Modulation, Dev etc..)

    You can start with one of the configurations which has little higher has your desired data rate under Typical settings then change the RF parameters to the desired values then export the Register settings and use it.

    Also please verify the Tx Frequency Accuracy on your product. If it requires tune the Loading Caps on the Crystal (26MHz) for better freq accuracy. You can test the Frequency Accuracy in Continuous TX - Unmodulated mode ( please refer to SmartRF Studio).  If you use Spectrum Analyzer for this measurement then set the Span to  < 10 KHz for better frequency resolution.

    Please retest with the Register settings from the SmartRF Studio and with the above recommended filter BW then let us know the result.

    Thanks,

    PM