Rainbow Electronics AT86RF231 - Manual (Page 142)

142
8111A–AVR–05/08
AT86RF231
11.4 Antenna Diversity
The Antenna Diversity implementation is characterized by:
• Improves signal path robustness between nodes
• AT86RF231 self-contained antenna diversity algorithm
• Direct register based antenna selection
11.4.1 Overview
Due to multipath propagation effects between network nodes, the receive signal strength may
vary and affect the link quality, even for small changes of the antenna location. These fading
effects can result in an increased error floor or loss of the connection between devices.
To improve the reliability of an RF connection between network nodes Antenna Diversity can be
applied to reduce effects of multipath propagation and fading. Antenna Diversity uses two anten-
nas to select the most reliable RF signal path. This is done by the radio transceiver during
preamble field search without the need for microcontroller interaction. To ensure highly indepen-
dent receive signals on both antennas, the antennas should be carefully separated from each
other.
If a preamble field is detected on one antenna, this antenna is selected for reception. Otherwise
the search is continued on the other antenna and vice versa.
Antenna Diversity can be used in Basic and Extended Operating Modes and can also be com-
bined with other features and operating modes like High Data Rate Mode and RX/TX Indication.
11.4.2 Antenna Diversity Application Example
A block diagram for an application using an antenna switch is shown in Figure 11-10 on page
142 .
Figure 11-10. Antenna Diversity - Block Diagram
6
5
4
3
2
1
9 10
AT86RF231
DIG3
DIG4
AVSS
RFP
RFN
AVSS
DIG
1
DI
G
2
Ba
lu
n
ANT0
ANT1
RF
-
Sw
it
c
h
B1 SW1
...