13.2.1 ATWINC3400-MR210UA Module Placement and Routing Guidelines
The ATWINC3400-MR210UA module has an Ultra Small Miniature RF Connector (u.FL) for the external antenna. The choice of antenna is limited to the antenna types for which the module was tested and approved. 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 the ATWINC3400-MR210UA module is shown in ATWINC3400-MR210UA Approved External Antennas.
It is critical to follow the recommendations listed below to achieve the best RF performance:
- Avoid routing any traces on the top layer of the host board, which is directly below the module area.
- Place the GND polygon pour below the complete module area. Do not have any breaks in this GND plane.
- Place sufficient GND vias in the GND polygon pour below the module area for better RF performance.
- Having 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 is recommended. This will act as a good ground and thermal conduction path for the ATWINC3400-MR210UB module. The GND vias must have a minimum via hole size of 0.3 mm.
- Keep large metal objects away from the external antenna to avoid electromagnetic field blocking.
- Make sure the width of the traces routed to GND, VDDIO and VBAT rails are sufficiently larger for handling the peak TX current consumption.
Antenna Placement Recommendations for ATWINC3400-MR210UA
The following recommendations must be applied for the placement of antenna and its cable:
- The antenna cable must not be routed over circuits generating electrical noise on the host board or alongside or underneath the module. It is preferable that the cable be routed straight out of the module.
- The antenna must not be placed in
direct contact or in close proximity of the plastic casing/objects.
- Do not enclose the antenna within a metal shield.
- Keep any components that may radiate noise, signals or harmonics within the 2.4 GHz to 2.5 GHz frequency band away from the antenna and, if possible, shield those components. Any noise radiated from the host board in this frequency band degrades the sensitivity of the module.
- It is recommended that the antenna be placed at a distance greater than 5 cm away from the module. The following figure shows the antenna keepout area; the antenna must not be placed in this area.
- This recommendation is based on an open-air measurement and does not take into account any metal shielding of the customer end product. When a metal enclosure is used, the antenna can be located closer to the ATWINC3400-MR210UA module.
- The drawing provides an option for routing the antenna cable depending on the location of the antenna with respect to the ATWINC3400-MR210UA PCB. There are two possible options for the optimum routing of the cable.
