User`s manual

OEM User’s Manual 33

4.3 Wi-Fi

Figure 10 shows a functional block diagram for the Wi-Fi circuits.

Figure 10. RCM5600W Wi-Fi Block Diagram

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 the serial flash and is loaded into an SRAM for execution when

power is applied to the RCM5600W modules. The data interface between the processor

MAC and the AL2236 transceiver consists of a D/A converter and an A/D converter. Both

converters 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.

U15

Antenna

Switch

XCVR

AL2236

Rx Path

Tx Path

Baseband

3-wire serial bus

Serial

Flash

U10

SRAM