USX2-433-5 데이터 시트보기 (PDF) - Radiometrix Ltd
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USX2-433-5 Datasheet PDF : 9 Pages
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RX Received Signal Strength Indicator (RSSI)
The USX2 has wide range RSSI that 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 9 of the module has a standing DC bias of up to 0.5V with no signal, rising to 2.5V at
maximum indication (RF input levels of -40dBm and above). ∆Vmin-max is typically 2V and is largely
independent of standing bias variations. Output impedance is 4.7kΩ. The pin has a 1nF cap to ground.
Digital RSSI output
In serial mode, RSSI can be read back as a digital value on pin P3. The RSSI read back command initiates a
read of the analogue RSSI value (as present on pin 9) by an internal 8 bit A/D converter.
This converter uses the 3.0v rail as it's reference (so an RSSI voltage of 3v will give a read back of 255,
while a voltage of 0v will read back 00).
Practically, the RSSI circuit produces about 0.5 - 2.5v (read back value 40 - 212) and this voltage is related
(approximately) to the receiver input level by the graph below.
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-140 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40
RF level (dBm)
Figure 4: typical RSSI level with respect to received RF level at USX2 antenna pin
The table below relate the receiver input level to the typical analogue voltage output at pin 9 and the
corresponding digital RSSI value read back at pin 3 (in serial mode).
RF power (dBm)
No signal
-120
-110
-100
-90
-80
-70
-60
-50
-40
Analogue RSSI (V) at pin 9
0.45
0.65
0.85
1.2
1.4
1.65
1.95
2.2
2.3
2.35
Digital RSSI value (on pin 3)
36 (24h)
53 (35h)
75 (4Bh)
101 (65h)
123 (7Bh)
141 (8Dh)
166 (A6h)
187 (BBh)
198 (C6h)
200 (C8h)
Please note, the RSSI graph and the table values above are for indicative purposes only and is not a
guarantee of actual RSSI characteristics.
Radiometrix Ltd
USX2 Data Sheet
page 7
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