Wi-Fi - Rabbit RabbitCore RCM5400W User Manual

4.3 Wi-Fi

Figure 9 shows a functional block diagram for the Wi-Fi circuits.
U17
U4 or U12
Serial
Parallel
Flash
Flash
U2, U3, U11
SRAM
The Wi-Fi transmission is controlled by the Rabbit 5000 chip, which contains the Wi-Fi
Media Access Control (MAC). The Rabbit 5000 implements the 802.11b/g baseband
MAC functionality, and controls the 802.11b/g integrated Airoha AL2236 transceiver.
Program code is stored in parallel flash and is loaded into a fast SRAM for execution
when power is applied to the RCM5400W modules. Serial flash and low-power SRAM
memories are available for data storage. The data interface between the processor MAC
and the AL2236 transceiver consists of a D/A converter and an A/D converter. Both con-
verters convert "I" and "Q" data samples at a rate of 40 MHz.
The AL2236 is a single-chip transceiver with integrated power amplifier for the 2.4 GHz
Industrial, Scientific, and Medical (ISM) band. It is configured and controlled by the
Rabbit 5000 via a 3-wire serial data bus. The AL2236 contains the entire receiver, trans-
mitter, VCO, PLL, and power amplifier necessary to implement an 802.11b/g radio.
The AL2236 can transmit and receive data at up to 11Mbits/s in the 802.11b mode and at
up to 54 Mbits/s in the 802.11g mode. It supports 802.11b/g channels 1–13 (2.401 GHz to
2.472 GHz). Channel 14 is not used. The data modulate the channel carrier in such a way
so as to produce a spread spectrum signal within the 22 MHz channel bandwidth of the
selected channel. The channel numbers and associated frequencies are listed below in
Table 4.
The Wi-Fi channels have a certain amount of overlap with each other. The further apart
two channel numbers are, the less the likelihood of interference. If you encounter interfer-
ence with a neighboring WLAN, change to a different channel. For example, use channels
1, 6, and 11 to minimize any overlap.
OEM User's Manual
Rx
Baseband
Tx
Baseband
3-wire serial bus
Figure 9. RCM5400W Wi-Fi Block Diagram
Rx Path
U18
AL2236
XCVR
Tx Path
P2
U19
Antenna
P1
Switch
39