MRF39RA datasheet(9/72 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS40001778B-page 9

MRF39RA

Table 2-2 summarizes the performance (typical

figures) of the complete receiver.

2.4.2.1

RssiThreshold Setting

For

correct

operation

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.

EQUATION 2-4:

AGC REFERENCE LEVEL

TABLE 2-2:

RECEIVER PERFORMANCE SUMMARY

Input Power Pin

Gain

Setting

Receiver Performance (typ.)

P-1dB

[dBm]

[dB]

IIP3

[dBm]

IIP2

[dBm]

Pin < AgcThresh1

-37

-18

+35

AgcThresh1 < Pin < AgcThresh2

-31

-15

+40

AgcThresh2 < Pin < AgcThresh3

-26

-8

+48

AgcThresh3 < Pin < AgcThresh4

-14

-1

+62

AgcThresh4 < Pin < AgcThresh5

>-6

+13

+68

AgcThresh5 < Pin

+20

+75

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.

Where:

NF = 7 dB

: LNA’s Noise Figure at maximum gain

DemodSnr = 8 dB

: SNR needed by the demodulator

RxBw

: Single sideband channel filter bandwidth

FadingMargin = 5 dB

: Fading margin

AGC Reference [dBm]

174

–

DemoSnr

10.

2RxBw

 FadingMargin dBm



log

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