nRF52832 front end tuning

[BTFrank]

When I'm tuning the RF output (front end) of the nRF52832 to match 50 Ohm what state should the chip be in?  Unprogrammed with power on or off?  Or in receive mode with power on?  This is with the VNA looking into the chip's RF output.

[Marjeris Romero]

Hi Frank,

We usually don't use a VNA for tuning the radio matching network. It will only tell you the impedance when you look into the matching network but will not give you any information about the actual output power, level of harmonics or spurious in RX mode.

The matching network of the radio will be optimal in both RX and TX mode if the TX output power is maximized at the same times as the harmonics and the RX LO are minimized. When measuring output power and harmonics for TX we set the radio to send an unmodulated TX carrier and check the tuning for channels 02, 40 and 80. You can use the radio_test example for setting up the TX carrier.

We have a whitepaper on 'RF Performance Test Guidelines' you can take a look at for more information here.

A VNA is useful for antenna measurements. Keep in mind you need extra components to match the antenna, L1 and C3 are the matching components for the radio.

Best regards,

Marjeris