MRF39RA Datasheet, PDF (9/72 Pages) Microchip Technology – Low-Power, Integrated UHF Receiver

MRF39RA
Table 2-2 summarizes the performance (typical
figures) of the complete receiver.
TABLE 2-2: RECEIVER PERFORMANCE SUMMARY
Input Power Pin
Pin < AgcThresh1
AgcThresh1 < Pin < AgcThresh2
AgcThresh2 < Pin < AgcThresh3
AgcThresh3 < Pin < AgcThresh4
AgcThresh4 < Pin < AgcThresh5
AgcThresh5 < Pin
Gain
Setting
G1
G2
G3
G4
G5
G6
P_-1dB
[dBm]
-37
-31
-26
-14
>-6
>0
Receiver Performance (typ.)
NF
[dB]
7
13
18
27
36
44
IIP3
[dBm]
-18
-15
-8
-1
+13
+20
IIP2
[dBm]
+35
+40
+48
+62
+68
+75
2.4.2.1 RssiThreshold Setting
For correct operation of the AGC, set the
RssiThreshold in RegRssiThresh to the sensitivity of
the receiver. The receiver remains in Wait mode until
RssiThreshold is exceeded.
2.4.2.2 AGC Reference
The AGC reference level is automatically computed in
the MRF39RA, according to the formula in Equation 2-4.
Note:
When AFC is enabled and automatically
performed at the receiver start-up, the
channel filter used by the receiver during
the AFC and AGC is RxBwAfc instead of
the standard RxBw setting. This may
impact the sensitivity of the receiver and
the setting of RssiThreshold accordingly.
EQUATION 2-4: AGC REFERENCE LEVEL
AGC Reference [dBm] = – 174 + NF + DemoSnr + 10.log 2^RxBw + FadingMargindBm
Where:
NF = 7 dB
DemodSnr = 8 dB
RxBw
FadingMargin = 5 dB
: LNA’s Noise Figure at maximum gain
: SNR needed by the demodulator
: Single sideband channel filter bandwidth
: Fading margin
 2015 Microchip Technology Inc.
DS40001778B-page 9