energy efficiency on NFC06A1 board

[TZhou.2]

Hi, As I want to measure the energy efficiency on the NFC06A1 board. Could you provide the testing position of the VDD_RF pin on PCB board? And do you have a clear tutorial about your antenna auto-tuning system? The third problem is about AAT technology

As you can see the pin of VDD_DR and VDD_RF in schematic.

[Ulysses HERNIOSUS]

Hi,

concerning AAT, I responded in this thread mcu-control-the-antenna-function-of-st25r3916.

Measuring the VDD_RF current is not easily possible on NFC06. You could however measure the power provided to VDD which will include the power going into VDD_RF. I expect the VDD power to be dominated by VDD_RF power once the field is turned on.

As an alternative you could also use the ST25R3916-DISCO board MB1414 where you have the option to bypass the internal regulators and to connect your own power source.

Not all power entering in VDD_RF will exit on the antenna. Depending on matching and antenna you may see also considerable losses on ST25R316 driver and matching components. You would need to either estimate the heat losses or estimate the power inside the carrier field.

Best Regards, Ulysses

[TZhou.2]

One question about Automatic antenna tuning (AAT) code on NFC06A1:

As u know, st25r3916_aat.c is used for the antenna tuning algorithm tries to find the optimal settings for the AAT_A and AAT_B registers, which are connected to variable capacitors to tune the antenna matching. But I am not familiar with this code, could you get me a tutorial about how to configure this code to tune my antenna? And can it change TX power? thanks

[Ulysses HERNIOSUS]

Hi,

the algorithm is descripted a bit in AN5322 ch.9. It is a hill climb algorithm tries to get weight function f() into a minimum. f() receives two input parameters: The measured amplitude and the measured phase.

Depending on the input parameters you may be able to increase the output power as the amplitude will often have a positive correlation to TX power. Typically the parameters are set such that we also stay well below the voltage limit of the RFI pins.

Best Regards, Ulysses