Fixed frequency samples for CE Certification

[Dhiraj]

Hello Everyone,

I am using raytac's BLE module (nrf51822 chip antenna version, 32kb RAM 256 kb Flash ) (www.raytac.com/download/MDBT40/MDBT40-ANT-D.pdf) in our product. We have to apply for CE certifcate. Testing lab has asked for fixed frequency samples.

Regarding the fixed frequency samples, Normally, For blue tooth products, We need to set the frequency to a fixed MHz for testing,(Normally we set at 2402/2441 or 2480). And Bluetooth supplier known this clearly. And the testing lab need 2pcs fixed frequency PCBA samples."

I came across this question which is similar: devzone.nordicsemi.com/.../

Does that mean I have to upload the radiotest firmware and provide it to testing lab? How to provide fixed frequency samples to testing lab? Thank you in advance.

[Hung Bui]

Could you clarify with the test lab that what kind of signal at fixed frequency they want to see ?

If they just need a constant carrier signal, then you can use the radio_test example.

If they need BLE packet (assuming advertising packet) sending at a fixed channel, then you need to write the code to do the change in ble_gap_adv_ch_mask_t in ble_gap_adv_params_t to select the channel you want to advertise.

[Dhiraj]

For now lab has just asked for fixed frequency samples (for example: radio at frequency : 2402MHz). I am assuming it to be constant carrier signal. I will reconfirm it. Is softdevice required in radiotest example? I ran radiotest example, and provided command over UART using putty terminal. How do I verify whether the correct frequency emitted?

[Hung Bui]

You can use nRFGo Studio-> Direct test mode and use another board as receiver. You need to flash the DTM example in the SDK to do that test. DTM can do the same thing as radio test example. But the radio test example is more simple.

The softdevice usually is not needed by the lab.

[Dhiraj]

Hello Hung,

Thank you for reply. Correct me if I am wrong. One module will have DTM example code flashed. Then open nRFGo studio and then change the required settings like channel, modes, etc. Only the module which has DTM example flashed can work with Direct test mode option present in nrfGostudio.

use another board as receiver.

• How can I do this? How to check whether receiver is receiving data at correct frequency?

[Hung Bui]

Hi again, sorry I was thinking about other test mode where you actually send payloads. In constant carrier there will be no payload simply radio signal with no modulation.

My idea was to use the radio_test as transmitter, and then use another board running DTM, connect to nRFGo Studio to work as receiver. But this won't work with the constant carrier.

To verify the correct frequency emitted, you would need to use a spectrum/network analyzer.

[Dhiraj]

I don't have Spectrum/network analyzer and they are too costly :( I have tested the radio example and it worked fine, so i will forward two samples with radio test example with some necessary changes. I will the set variable "channel_start" in radio_test example to fixed number to get fixed frequency instead of getting data via UART.