SWRS046I November 2006 – September 2018 CC1020
PRODUCTION DATA.
The CC1020 device has a built-in feature called AFC (Automatic Frequency Control) that can be used to compensate for frequency drift.
The average frequency offset of the received signal (from the nominal IF frequency) can be read in the AFC register. The signed (2’s-complement) 8-bit value AFC[7:0] can be used to compensate for frequency offset between transmitter and receiver.
The frequency offset is given by Equation 22.
The receiver can be calibrated against the transmitter by changing the operating frequency according to the measured offset. The new frequency must be calculated and written to the FREQ register by the microcontroller. The AFC can be used for an FSK/GFSK signal, but not for OOK. Application Note AN029 CC1020/1021 Automatic Frequency Control (AFC) (SWRA063) provides the procedure and equations necessary to implement AFC.
The AFC feature reduces the crystal accuracy requirement.