How to maximize DUTY with PRBS9 using DTM?

[toshi.g]

Hello,

I will place an order with a testing company to test EN300328 emissions for a product using the nRF52840.
I received an instruction from the testing company to prepare a sample with the following conditions.

 1.Continuous modulation transmission
 2.Transmission CH is minimum and maximum
 3. Maximum Duty
 4.PRBS9
 5. Maximum transmission power

I want to set this condition using Direct Test Mode V2.02.
(Direct Test Mode is running on a PC.)
I have set below.

  CHANNEL MODE:Single
  Transmit on channel: 37/39
  Transmit power: 8dbm
  Physical layer: LE Coded S8/LE 1Mbps
  Packet type: PRBS9
  Packet Length: ?
 No timeout

So here's the question.
Q1.
There is no duty in the setting items, but what is the duty percentage?

Q2.
How can I set the duty to maximum?

Q3.
Any value for Packet length has nothing to do with the necessary conditions?
Perhaps there is a relationship between Packet length and Duty?

that's all. Thank you.

[ketiljo]

Contiguous transmission is not possible with DTM. It will be about 60%

The only possible way to setup a modulated carrier with 100% duty cycle is to use the radio test example from the SDK. 

NSC https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/peripheral/radio_test/README.html 

nRF5: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/nrf_radio_test_example.html

This is straight forward to use with CLI over UART. 

[toshi.g]

thank you for your answer.

Q1.
Do you agree with this understanding?
　1.If I use start_duty_cycle_modulated_tx in radio_test, I can set a random value with duty99% and send it.

   2.Random value seems to be generated by nrf_rng_random_value_get.

Q2.
 I have been requested by a certification body to:

 According to the standard, it is necessary to test in a state that gives the worst result.
 There is no problem if you can guarantee that the method(nrf_rng_random_value_get) other than PRBS9 is Worst.

 Will nrf_rng_random_value_get meet this requirement?

that's all. Answer please.

[ketiljo]

toshi.g said:

　1.If I use start_duty_cycle_modulated_tx in radio_test, I can set a random value with duty99% and send it.

It's better to use start_tx_modulated_carrier as this will give you 100% duty cycle

toshi.g said:

2.Random value seems to be generated by nrf_rng_random_value_get.

Yes, this have random payload

toshi.g said:

 According to the standard, it is necessary to test in a state that gives the worst result.
 There is no problem if you can guarantee that the method(nrf_rng_random_value_get) other than PRBS9 is Worst.

Yes, this will give the widest carrier bandwidth as the data is random, similar to PRBS9. PRBS is just a method to generate random numbers. 

[toshi.g]

I understood as follows.
 1.When start_tx_modulated_carrier is used, a random value is continuously transmitted with a

  duty of  100%.
 2. This random value may be treated the same as the value generated by PRBS9.

I would request a certification agency to evaluate using a program that contains start_tx_modulated_carrier.

Thank you for your answer.

[ketiljo]

toshi.g said:

 1.When start_tx_modulated_carrier is used, a random value is continuously transmitted with a

Correct!

toshi.g said:

 2. This random value may be treated the same as the value generated by PRBS9.

Coreect!

[toshi.g]

Hello,
I used start_tx_modulated_carrier to measure radio waves at communication speeds of

2Mbit, 1Mbit, 500Kbit, and 125Kbit.

I am concerned that the measured waveform at a communication speed of 125 Kbit

is not smooth and has two sharp peaks.

Are these measurement results normal?

That's all for the question.