CC2651R3SIPA: EMI Peaks at 2.4GHz above FCC EMI Limits

Hi Mar,

Q1. I will need help from the FCC certification experts currently out of the office until next week, I will come back to you as soon I have answers.

Q2. Reducing the transmit power will reduce the EMI, take a look at HCI_EXT_SetTxPowerCmd() in the API documentation for information.

Q3. The recommended advertisement interval time should be defined according to your use case. Take a look at the Advertising Parameters in the Scanning and Advertising Basics SLA for more information.

Regards,
Tanguy

Hello Mar,

If the device is used according to the requirements noted in https://www.ti.com/lit/an/swra748/swra748.pdf then there should be no issue. I am curious about your test results as you haven't included the limits you are using, the test setup, or the actual measured values. It's not really feasible to evaluate the results without that information. The data provided doesn't really make sense as the FCC limit for the 2.4GHz – 2.4835GHz band is +21dBm and the maximum transmit power for CC2651R3SIPAT0MOUR is +5dBm. See https://www.ti.com/lit/an/swra048/swra048.pdf for more information on FCC limits.

Thanks,

Jake

Hi Mar,

Your advertising channels line up with the information you provided above:

2426MHz = Channel 38

2402MHz = Channel 37

Channel 37, 38 are the advertising channels so I would expect activity on them.

For output power a conducted (connected to test equipment via coaxial cable) measurement is performed rather than a radiated measurement.

What are you referencing when setting those limits? Those look like the limits for band edge testing but wouldn't be applicable in the intentional radiator frequency band.

For my understanding, what specific FCC requirement are you trying to evaluate or test? For example the band edge evaluation might look something like:

where any spurious emissions or intended emissions cannot have energy out past the band edge up to the limit provided. This image is from our certification report for CC2651R3SIPA (https://dr-download.ti.com/design-tools-simulation/certification/MD-gej3rHqrPC/7.20.00.00/CC2651R3SIPAT0MOUR_Cert_Reports_7_20_00_00.zip). Maybe it would be good to look at those reports and compare them against your results. These test reports describe the test conditions and the limits. If you're seeing similar results then you should be good.

In particular maybe look at FR242614A_R01_Part15C_TI_CC2651R3SIPA.pdf which is the Bluetooth low energy report. Appendix E and F show the band edge limits. 

BR,

Jake