Continuous modulated carrier for FCC

[Remo]

Hi all

I found the following thread that mentions that the "radio test example" can be used for FCC testing: devzone.nordicsemi.com/.../

Now the certification lab requires, amongst others, a modulated carrier with a duty cycle over 99%. From the "radio test example" I would use the function "radio_modulated_tx_carrier" to generate the modulated carrier. But the duty cycle is only 96% (measured on the VDD_PA signal).

Therefore, instead of the shortcuts from the original example:

NRF_RADIO->SHORTS = (
   RADIO_SHORTS_END_DISABLE_Msk | 
   RADIO_SHORTS_READY_START_Msk | 
   RADIO_SHORTS_DISABLED_TXEN_Msk);

I tried the following shortcuts:

NRF_RADIO->SHORTS = (
   RADIO_SHORTS_READY_START_Msk |
   RADIO_SHORTS_END_START_Msk);

With it, I get a duty cycle of 100%. But according to chapter "17.1.9 Maximum consecutive transmission time" of the nRF51 reference manual, the maximum transmission time should not exceed 16ms.

Is that a problem for this special FCC test mode? If yes, what do you suggest to get the duty cycle of 99% for this test mode?

Kind regards

Remo

[run_ar]

The duty cycle does not have to be over 99%. If you look at chapter 10.5 in the FCC measurment guidance, the document on the bottom of this page. You can see that a different test method apply when the EUT cannot be configured to transmit continuously.

The shortcuts you configured will cause the pll to drift. I would not recommend using this configuration.

[Remo]

Many thanks for the clarification!