Rssi Output - Texas Instruments Chipcon Products CC1000-RTB1 Manual

22. RSSI output

CC1000
has a built-in RSSI (Received
Signal Strength Indicator)
analogue output signal at the RSSI/IF pin.
The IF_RSSI bits in the FRONT_END
register enable the RSSI. When the RSSI
function is enabled, the output current of
this pin is inversely proportional to the
input signal level. The output should be
terminated in a resistor to convert the
current output into a voltage. A capacitor
is used in order to low-pass filter the
signal.
The RSSI voltage range from 0 – 1.2 V
when using a 27 kΩ terminating resistor,
giving approximately 50 dB/V. This RSSI
voltage can be measured by an A/D
converter. Note that a higher voltage
means a lower
RSSI/IF RSSI/IF
CC1000 CC1000
C281 C281
Figure 21. RSSI circuit
giving an
input signal.
TO ADC TO ADC
R281 R281
SWRS048A
The RSSI measures the power referred to
the RF_IN pin. The input power can be
calculated using the following equations:
P = -51.3 V – 49.2 [dBm] at 433 MHz
RSSI
P = -50.0 V – 45.5 [dBm] at 868 MHz
RSSI
The external network for RSSI operation is
shown in Figure 21. R281 = 27 kΩ, C281
= 1nF.
A typical plot of RSSI voltage as function
of input power is shown in Figure 22.
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-105 -100 -95 -90 -85
Figure 22. RSSI voltage vs. input power
CC1000
433Mhz
868Mhz
-80 -75 -70 -65 -60 -55 -50
dBm
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