Antenna Diversity

This section describes the configuration and usage of the MAC based Antenna Diversity (AD) feature.

Antenna diversity uses two antennas to select the most reliable RF signal path. This may lead to an improved robustness of the entire network connection, because impacts of multipath propagation and fading can be reduced.

Parameters:

	extswen	control of external RF switch using differential pin pair DIG1/DIG2: {0} output pins DIG1 and DIG2 are pulled-down to digital ground, {1} output pins DIG1 and DIG2 are enabled thus providing a differential control signal for a RF switch.
	antctrl	antenna selection; {1} select antenna 0 (DIG1=L, DIG2=H), {2} select antenna 1 (DIG1=H, DIG2=L), {0,3} reserved.

Note:: >> In order to reduce the power consumption in the states TRX_OFF or SLEEP, the RF switch control shall be disabled (extswen=0).
>> If RX Frame Time Stamping is used in combination with the antenna diversity feature, the pin DIG1 controls the RF switch and the pin DIG2 is used for RX frame time stamping. In this case, the radio transceiver does not provide a differential RF switch control signal.
>> If RF switch control is disabled (extswen=0), the sub register SR_ANT_CTRL shall be set to its default value antctrl=1.

Use Cases:

SET_ANTENNA

An antenna can be selected by enabling the RF switch control extswen=1 and configuring antctrl.

Note:: Setting an antenna takes effect immediately and thus may disturb an ongoing transmit or receive transaction. Therefore, setting the antenna should not be carried out in any of the [BUSY] states.

Code example

    /* AT86RF212::[CONFIG] */
    trx_bit_write(SR_ANT_CTRL, antctrl);
    trx_bit_write(SR_ANT_EXT_SW_EN, 1);

GET_ANTENNA

The current selected antenna (see antctrl) can be read from sub register SR_ANT_CTRL whenever the radio transceiver is in one of the [ACTIVE] states.

Code example

    /* AT86RF212::[ACTIVE] */
    antctrl = trx_bit_read(SR_ANT_CTRL);
    proc_antenna(antenna);