Data Sheet

LJ1269HC
Rev1.0 Page 27 Web: www.ljelect.com
Note : this filter is automatically bypassed when receiving FSK signals (ModulationType = 00 in RegDataModul).
3.4.8. RSSI
The RSSI block evaluates the amount of energy available within the receiver channel bandwidth. Its resolution is 0.5 dB, and it
has a wide dynamic range to accommodate both small and large signal levels that may be present. Its acquisition time is very
short, taking only 2 bit periods. The RSSI sampling must occur during the reception of preamble in FSK, and constant “1”
reception in OOK.
Note - RssiValue can only be read when it exceeds RssiThreshold
- The receiver is capable of automatic gain calibration, in order to improve the precision of its RSSI measurements. This function
injects a known RF signal at the LNA input, and calibrates the receiver gain accordingly. This calibration is automatically
performed during the PLL start-up, making it a transparent process to the end-user
- RSSI accuracy depends on all components located between the antenna port and pin RFIO, and is therefore limited to a few
dB. Board-level calibration is advised to further improve accuracy
Figure 8. RSSI Dynamic Curve
3.4.9. Cordic
The Cordic task is to extract the phase and the amplitude of the modulation vector (I+j.Q). This information, still in the digital
domain is used:
 Phase output: used by the FSK demodulator and the AFC blocks.
 Amplitude output: used by the RSSI block, for FSK demodulation, AGC and automatic gain calibration purposes.
Sub GHz FSK/OOK Transceiver Module DATASHEET