MRF39RA Datasheet, PDF (13/72 Pages) Microchip Technology – Low-Power, Integrated UHF Receiver

MRF39RA
2.4.8 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, only
taking 2-bit periods. The RSSI sampling must occur
during the reception of preamble in FSK and constant
‘1’ reception in OOK. Figure 2-4 shows the RSSI
dynamic curve.
Note 1: RssiValue can only be read when it
exceeds RssiThreshold.
2: RssiStart command and RssiDone flags
are not usable when DAGC is turned on.
See Section 2.4.3 “Continuous-Time
DAGC”.
3: The receiver is capable of automatic gain
calibration 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.
4: RSSI accuracy depends on all
components located between the
antenna port and pin RFIO and is
therefore limited to a few decibels.
Board-level calibration is advised to
further improve accuracy.
FIGURE 2-4:
RSSI DYNAMIC CURVE
RSSI Chart Zith AGC
0.0
-20.0
-40.0
-60.0
-80.0
-100.0
-120.0
-120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0
Pin dBm
 2015 Microchip Technology Inc.
DS40001778B-page 13