sx1231h Semtech Corporation, sx1231h Datasheet - Page 28

• Manufacturer Part Number: sx1231h
• Description: Low Power Integrated Uhf Transceiver With On-chip +20dbm Pa
• Manufacturer: Semtech Corporation

Note
3.4.10. 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:
Rev 1 - Oct 2011
ADVANCED COMMUNICATIONS & SENSING
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.
- 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
-100.0
-120.0
-20.0
-40.0
-60.0
-80.0
0.0
-120
-110
Figure 9. RSSI Dynamic Curve
-100
Figure 10. Cordic Extraction
Magnitude
Real-time
-90
RSSI Chart - With AGC
-80
Page 28
-70
Pin [dBm]
Q(t)
-60
Real-time Phase
-50
I(t)
-40
-30
-20
-10
0
SX1231H
DATASHEET
www.semtech.com