AT86RF211SAHW Atmel, AT86RF211SAHW Datasheet - Page 13

• Manufacturer Part Number: AT86RF211SAHW
• Manufacturer: Atmel

Specifications of AT86RF211SAHW

• Lead Free Status / Rohs Status: Compliant

4.2
4.2.1
4.2.2
4.2.3
Figure 4-6.
e2v semiconductors SAS 2008
Receiver Description
Intermediate Frequencies
Rx/Tx Switch
Image Rejection and RF Filter
Typical 50Ω SAW Filter Implementation in the 868 MHz Bandwidth
SWOUT (pin 48)
SPST Switch
For selectivity and flexibility purposes, a classic and robust 2 IF super-heterodyne architecture has been
selected for the AT86RF211S. To minimize the cost of the external components, the most popular IF val-
ues has been chosen that is 10.7 MHz. The impedances of the input/output of the mixing stages have
been internally matched to the most common ceramic filter impedances.
Note:
An SPST switch is integrated. In transmission mode, it protects the LNA input from the large voltage
swings of the Power Amplifier (PA) output (up to several volts peak-to-peak), which is switched to a high
impedance state. The SPST switch is automatically turned on or off by the Rx/Tx control bit. The inser-
tion loss is approximately 4 dB and the reverse isolation about 30 dB in a 300Ω environment.
The immunity of the AT86RF211S can be improved with an external band-pass filter.
For example, when using a SAW filter, it must be matched with the LNA input and the output of the
switch. The following diagram gives the typical implementation for an
868 MHz application with a 50Ω/50Ω SAW filter.
See
Transceiver for ISM Radio Applications - RF BOM versus. Application Requirements”, for suggested
matching filters.
Table 4-3 on page 14
IF1 can be any frequency but must match available ceramic filters.
2.2 nH
for precise matching information and the Application Note “AT86RF211S
These inductors can be printed
SAW
50 Ω
12 nH
(pin 45)
RXIN
0894C–WIRE–11/08
AT86RF211S
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