2.9.2 Antenna Tuning

For applications using a loop antenna, the ATA8510/15 offers an automatic antenna-tuning feature that improves antenna performance by compensating for hand effects or matching component value variations. Antenna tuning maximizes the radiated power of the loop antenna during transmission by changing an internal capacitor behind pin 5 (ANT_TUNE).

The specified tuning value can also be used for receiving, thus optimizing loop antenna matching.

As long as no antenna tuning process was performed after power-on, an initialization value is used from the EEPROM. The value can be configured independently for each service in the eepServices.FEAT.ANTN[3:0] variables. The default value is 7.

Address Service0

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x00CD

FEAT

————

ANTN[3:0]

An automatic antenna-tuning process can be activated at the following time points:

  • After power-on during system initialization when enabled in eepConfValid.confInitFlags.AntTune.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x0008

confInitFlags

AntTune

TempMeas

SRC

FRC

————
  • During start-up of TXMode as the operating mode after system start if enabled in eepTrxConf.sysStartConfig.ANT_TUNE.
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0x0019 sysStartConfig RF_CAL ANT_TUNE VCO_TUNE IDLEModeSelector — TMDEN OPM[1:0]
  • During start-up of TXMode via the “Set System Mode” SPI command (see Set System Mode).
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
systemModeConfig RF_CAL ANT_TUNE VCO_TUNE IDLEModeSelector — TMDEN OPM[1:0]
  • From IDLEMode via the “Calibrate and Check” SPI command if bit EN_ANT_TUNE in tuneCheckConfig is set to ‘1’ (see Calibrate and Check).

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

tuneCheckConfig

EN_ ANT_TUNE

EN_ TEMP_MEAS

EN_ SRCCAL

EN_ FRCCAL

EN_ VCOCAL

—

EN_SELF CHECK

—

Setting the ANT_TUNE bit to ‘1’ within the eepEventConf.cmdRdyConf command-ready variable raises a command-ready (CMD_RDY) event on the PB6 event pin after the antenna tuning process finishes.

Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0x0096 cmdRdyConf ANT_TUNE TEMP_MEAS SRC_CAL FRC_CAL VCO_CAL RF_CAL SELFCHECK TX

Antenna tuning requires additional time during mode start-up, see Timing Characteristics.

A description of the integrated antenna-tuning hardware can be found in Antenna Tuning. The application design is described in Antenna Tuning.