Transmitter Test of BlueNRG-MS

[rshar.21]

Hi Everyone,

I'm using STM32L4 microcontroller to communicate with BlueNRG-MS over SPI. 

I'm trying to create a firmware to get FCC certification and one of the parameter testing in that is Duty cycle (verification of spectrum/max energy in 1 MHz span). 

Below is the code snippet of how I'm configuring the rf transmission

 uint8_t test_payload = 0x04; // Psuedo random bit sequence 9 '11111111100000111101...'
 uint8_t test_payload_length = 0x25; 
 hApp->thisTrigger.SetTxpower = 7;
 hApp->thisTrigger.SetChannel = 0;
 hci_reset();
 HAL_Delay(100);
 ret = aci_hal_set_tx_power_level(1, hApp->thisTrigger.SetTxpower);
 HAL_Delay(10);
 ret = hci_le_transmitter_test(hApp->thisTrigger.SetChannel, test_payload_length, test_payload); 

 

But from above code, I'm receiving the duty cycle of ~12-20%. and the waveform of it as below

If you see waveform is coming right but in the span of 10MHz, whereas I want to achieve this in 1MHz span. 

One of the clue I can understand is either increase the RF transmission ON time or increase the frequency of the RF transmission(reduce the time between consecutive RF transmission). 

Can someone help me to figure out or understand to solve this problem?