RX3A Received Signal Strength Indicator (RSSI)
The RX3A receiver incorporates a wide range RSSI which measures the strength of an
incoming signal over a range of 60dB or more. This allows assessment of link quality and
available margin and is useful when performing range tests.
The output on pin 5 of the module has a standing DC bias of typically 0.25V with no signal,
rising to 1.1V at maximum indication. The RSSI output source impedance is high (~50kΩ) and
external loading should therefore be kept to a minimum.
Typical RSSI characteristic is as shown below:
RSSI (V)
1.2
1
0.8
0.6
0.4
0.2
0
-120
-110
-100
-90
-80
-70
-60
-50
RF input Level (dBm)
Fig.7: RX3A RSSI response curve
To ensure a reasonably fast response the RSSI has limited internal decoupling of 1nF to
ground. This may result in a small amount of ripple on the DC output at pin 5 of the module.
If this is a problem further decoupling may be added, in the form of a capacitor from pin 5 to
ground, at the expense of response speed. For example, adding 10nF here will increase RSSI
response time from 100µs to around 1ms. The value of this capacitor may be increased without
limit.
Radiometrix Ltd, TX3A & RX3A Data Sheet
page 8
RADIOMETRIX [ RADIOMETRIX LTD ]
