12 Design Guidelines

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

• When the module is placed on the motherboard, a provision for the antenna must be made. There must be nothing under the portion of the module that contains the antenna. This means the antenna must not be placed directly on top of the motherboard PCB. This can be accomplished by, for example, placing the module at the edge of the board such that the module edge with the antenna extends beyond the main board edge by 6.5 mm. Alternatively, a cutout in the motherboard can be provided under the antenna. The cutout must be at least 22 x 6.5 mm. Ground vias spaced 2.5 mm apart must be placed all around the perimeter of the cutout. No large components must be placed near the antenna.
• Keep large metal objects as far away from the antenna as possible to avoid electromagnetic field blocking.
• Do not enclose the antenna within a metal shield.
• Keep any components that may radiate noise or signals within the 2.4 – 2.5 GHz frequency band far away from the antenna or shield these components. Any noise radiated from the main board in this frequency band will degrade the sensitivity of the module.
• The main board must have a solid ground plane. Each ground pin of the module (including each of the center ground pads) must have a via placed either in the pad or right next to the pad going down to the ground plane.
• Place a 10 µF decoupling capacitor from the VBAT to the ground right next to pin 7. Place another 10 µF capacitor from VCC to ground right next to pin 21.
• Contact Microchip for assistance if any other placement is necessary.