Antenna tuning direct command

[DGabc.1]

ST25R3911B datasheet, section 1.2.21, paragraph "Antenna tuning using calibrate antenna direct command", indicates that the hardware algorithm uses a target phase (from the Antenna calibration target register).

AN4914, section 3, says:

Figure 18 shows the hardware-based AAT. This algorithm searches primarily the maximum amplitude of the input signal by changing the trim value. The target phase plays a minor role.

I am trying to understand what does the Antenna calibration target register represent - is it a target phase or a target amplitude?

[Ulysses HERNIOSUS]

Hi,

from the DS:

Antenna calibration target register Address: 22h

Function : Define target phase for Calibrate Antenna direct command

The command will first search for the target phase and after it has found it, it will maximize the amplitude. Often (depending on the used matching) this will just end up in maximum amplitude setting.

BR, Ulysses

[DGabc.1]

Hi Ulysses,

My understanding is that it tries to find the target phase by adjusting the trim capacitors. Once it has found the best setting for the trim capacitors, how does it maximize the amplitude? What will it do for that, exactly? If it changes the trim capacitors then will impact the phase it just adjusted for.

Thank you,

DG

[Ulysses HERNIOSUS]

Hi DG,

exactly, it will further adjust the trim caps to go to higher amplitude, thus typically moving away from the closest phase. That's why the target phase plays a minor role.

Regards, Ulysses