12.3 ATWILC1000-MR110UB Placement and Routing Guidelines

The ATWILC1000-MR110UB module has an Ultra Small Miniature RF Connector (U.FL) for the external antenna.

The choice of antenna is limited to the antenna types that the module was tested and approved for. For a list of tested and approved antennas that may be used with the module, refer to the respective country in the Regulatory Approval section.

An approved list of external antennas tested and certified with ATWILC1000-MR110UB module is shown in Table 12-1.

It is critical to follow the recommendations listed below to achieve the best RF performance:

1. Avoid routing any traces on the top layer of the host board, which is directly below the module area.
2. Place the GND polygon pour below the complete module area. Do not have any breaks in this GND plane.
3. Place sufficient GND vias in the GND polygon pour below the module area for better RF performance.
4. It is recommended to have a 3 x 3 grid of GND vias solidly connecting the exposed GND paddle of the module to the inner layer ground plane of the host board. This will act as a good ground and thermal conduction path for the ATWILC1000-MR110UB module. The GND vias must have a minimum via hole size of 0.3 mm.
5. Keep large metal objects away from the external antenna to avoid electromagnetic field blocking.
6. Do not enclose the external antenna within a metal shield.
7. Keep any components that may radiate noise or signals within the 2.4 GHz – 2.5 GHz frequency band away from the external antenna and if possible, shield those components. Any noise radiated from the host board in this frequency band will degrade the sensitivity of the module.
8. Make sure the width of the traces routed to the GND, VDDIO and VBAT rails are sufficiently larger for handling the peak TX current consumption.
9. The antenna should preferably be placed at a distance greater than 5 cm away from the module. The following figure shows the antenna keep out area indication; where the antenna must not be placed in this area. This recommendation is based on an open-air measurement and does not take into account by any metal shielding of the customer end product. When a metal enclosure is used, the antenna can be located closer to the ATWILC1000-MR110UB module.
   The following figure illustrates how an antenna cable should be routed based on the antenna’s location with respect to the ATWILC1000-MR110UB PCB. There are two possible options for the optimum routing of the cable.