Antenna Tuning
The Thingy:91 X Hello nRF Cloud firmware uses the Modem Antenna library to configure the nRF9151’s MIPI RF Front-End Control Interface (RFFE) and the COEX pins. The Modem Antenna library uses the %XMIPIRFFEDEV, %XMIPIRFFECTRL, and %COEXCONFIG AT commands to send the configuration to the nRF9151 modem. The Thingy:91 X board files define the default AT commands that are sent to the modem using the following Kconfig options:
CONFIG_MODEM_ANTENNA_AT_MIPIRFFEDEVCONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_INITCONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_ONCONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_OFFCONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_PWROFFCONFIG_MODEM_ANTENNA_AT_COEX0
The default values for the Kconfig options used when building firmware for the Thingy:91 X target can be found in the Thingy:91 X nRF9151 board configuration file.
You can modify the default values to optimize the antenna tuning of the Thingy:91 X for specific usage scenarios. Ignion, the manufacturer of the antenna used on the Thingy:91 X, explains in the Ignion Antenna Technology Powering The-Nordic-Thingy 91 X application note how the antenna tuning can be optimized for specific usage scenarios by adjusting the switching states of the antenna.
The antenna switch states can be set in the prj.conf file by changing the configuration of the %XMIPIRFFECTRL AT command or during runtime by issuing the AT%XMIPIRFFECTRL=<new_antenna_switch_states> AT command.
Important
Modification of the default configuration for the RF Front-End of the Thingy:91 X may result in radiated emissions outside regulatory limits. If you have a Thingy:91 X with a modified RF Front-End configuration, you must ensure that the operation of the modified Thingy:91 X complies with applicable regulatory requirements.