14.4.2.1 Overview

The AT86RF212B transceiver is split into an analog radio front-end and a digital domain. Referring to the receiver part of the analog domain, the differential RF signal is amplified by a low noise amplifier (LNA) and split into quadrature signals by a poly-phase filter (PPF). Two mixer circuits convert the quadrature signal down to an intermediate frequency. Channel selectivity is achieved by an integrated band-pass filter (BPF). The subsequent analog-to-digital converter (ADC) samples the receive signal and additionally generates a digital RSSI signal. The ADC output is then further processed by the digital baseband receiver (RX BBP), which is part of the digital domain.

The BBP performs further filtering and signal processing. In RX_ON state, the receiver searches for the synchronization header. Once the synchronization is established and the SFD is found, the received signal is demodulated and provided to the Frame Buffer. Upon synchronization the receiver performs a state change from RX_ON to BUSY_RX which is indicated by the TRX_STATUS bits in the TRX_STATUS register (TRX_STATUS.TRX_STATUS). Once the frame is received, the receiver switches back to RX_ON in the listen mode on the selected channel. A similar scheme applies to the Extended Operating Mode.

The receiver is designed to handle reference oscillator accuracies up to ±60ppm; refer to the f_SRD parameter in the General RF Specifications section. This results in the estimation and correction of frequency and symbol rate errors up to ±120ppm.

Several status information are generated during the receive process: LQI, ED, and RX_STATUS. They are automatically appended during Frame Read Access. Some information is also available through register access, for example the PHY_ED_LEVEL.ED_LEVEL and FCS correctness with the PHY_RSSI.RX_CRC_VALID.

The Extended Operating Mode of the AT86RF212B supports frame filtering and pending data indication.