MRF39RA datasheet(13/72 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS40001778B-page 13

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.

FIGURE 2-4:

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

automatically performed during the PLL

start-up, making it a transparent process

to the end user.

4: RSSI

accuracy

depends

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.

RSSI Chart

ith AGC

-120.0

-100.0

-80.0

-60.0

-40.0

-20.0

0.0

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

Pin dBm

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