FCC Certification /Digital modulation minimum bandwitdth

[LovejoySteph]

Hi all,

Our company is in the process of certifying a device. This device is using a nrf52832 with radio.

We had no problem to comply with the ETSI standard, but things didn't go as expected for FCC certification.

The FCC §15.247 says that for systems using digital modulation, the minimum 6 dB bandwidth shall be at least 500 kHz.

This is the radio setting I used: Tx Power = -4dBm, Frequency = 2402Mhz, Mode = 1Mbit

This is the result obtain by the test lab:

They found the highest point M3 and draw a line at -6dB. The bandwidth at -6dB from M3 should be at least 500kHz. Unfortunately from the test lab results, the bandwidth is only 483.2 kHz.

So my question is, is there a firmware way to changing the bandwidth for a fixe channel?

Thanks in advance for the help, Stéphane Lovejoy

[LovejoySteph]

Thanks AmbystomLabs for the previous comment.

As suggested by Bjørn Spockeli. I posted my question through the Mypage and they were able to help me.

They suggested to send random data, with the use of the radio test example to increases the bandwidth of the signal. Which seemed correct since I was only sending a fix data.

They also pointed that the radio was maybe not set up in BLE mode. Which was also correct since my radio was set to RADIO_MODE_MODE_Nrf_1Mbit

By modifying the radio mode to RADIO_MODE_MODE_Nrf_2Mbit and using the radio test example, I was able to obtain a 673 kHz bandwidh at 6dB

For the record, these are the result I obtain with 3 different radio mode:

1. RADIO_MODE_MODE_Nrf_1Mbit

2. RADIO_MODE_MODE_Nrf_2Mbit

3. RADIO_MODE_MODE_Ble_1Mbit