Datasheet

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SX1272/73
WIRELESS, SENSING & TIMING DATASHEET
Rev. 2 - July 2014
©2014 Semtech Corporation
Figure 44. AGC Steps Definition
The AGC reference power level is determined as follows:
AGC Reference [dBm]=-174 dBm + 10 * log(2 * RxBw) + SNR + AgcReferenceLevel
with SNR = 8 dB (considered a fixed value).
A detailed description of the receiver setup to enable the AGC is provided in section 4.2.7.
5.5.4. RSSI in FSK/OOK Mode
The RSSI provides a measure of the incoming signal power at RF input port measured within the receiver bandwidth. The
signal power is available in RssiValue. This value is absolute in units of dBm and with a resolution of 0.5 dB. The formula
below relates the register value to the absolute input signal level at the RF input port:
The RSSI value can be compensated to take into account the loss in the matching network or even the gain of an
additional LNA by using RssiOffset. The offset can be chosen in 1 dB steps from -16 to +15 dB. When compensation is
applied the effective signal strength is read as follows:
The RSSI value is smoothed on a user defined number of measured RSSI samples. The precision of the RSSI value is
related to the number of RSSI samples used. RssiSmoothing selects the number of RSSI samples from a minimum of 2
samples up to 256 samples in increments of power of 2.
Tab le 37 gives the estimation of the RSSI accuracy for a 10 dB
SNR and response time versus the number of RSSI samples programmed in RssiSmoothing.
Towards
-125 dBm
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Pin [dBm]
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AgcStep1
AgcStep2 AgcStep3 AgcStep4 AgcStep5
G1 G2 G3 G4 G5 G6
Higher Sensitivity
Lower Linearity
Lower Noise Figure
Lower Sensitivity
Higher Linearity
Higher Noise Figure
[] []
dBRssiOffsetdBmlevelRFRssiValue
+⋅−=
2
[]
2
RssiValue
dBmRSSI −=