MKW2x Transmit Power control

[roybenshlomo]

Hi,

I am trying to provide the maximal output power from my MKW21D256 based device. I also have an evaluation board (MK24D512 TWR) which runs the same code.

As I understand, the emitted power at the antenna port should be up to 4dBm.

I am using the register PA_PWR to control the power output and I do notice that changing it causes increase/decrease in output power.

The problem is, even using the maximal value for this register (0x1F), I get transmit power equal ~-6dBm (both on the TWR evaluation board and my custom board.

The data sheet is missing some detail about this register and specifies "See the power amplifier section for programming details (which I am not able to find on the same document).

Bottom line is, what is the maximal output power available on such devices (lets take for example the Freescale evaluation board and not my custom board), and how do I reach this maximal value? Currently, the best I can achieve is ~-6dBm at the antenna connector (I have no power conservation limitations).

Thanks in advance,

Roy.

[EarlOrlando]

Hello Roy,

In the section 4.6.2 RF Output Power Distribution in the MKW2xD Reference Manual (MKW2xDxxxRM.pdf) you can find the relation between the MKW2x TX power and the PA_PWR field in the Modem_PA_PWR register.

-6 dBm is a very low power, it is not normal. Maybe you have selected the SMA connector instead of the F-antenna. Please read the message in the link below and double check that you have selected the correct antenna through the capacitor.

Re: Kinetis KW2x - Debugging Radio Transmit / Receive

Best regards,

Earl!

[roybenshlomo]

earlorlandoramirez-sanchez​ Thank you for the response.

So, by default the TWR board is emitting the power through the SMA connector? Because the test I am describing was done with coaxial cables through the SMA connector.

Thanks,

Roy.

[EarlOrlando]

Hello Roy,

I am not sure but I believe that the F-antenna is selected by default. You need to verify in the board that the C17 capacitor is placed and the C18 isn't (i.e. there should be only one capacitor placed and it must be placed towards the preferred antenna).

Best regards,

Earl.