WT21-A-HCI 查看數據表（PDF） - Unspecified

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WT21-A-HCI

BLUETOOTH HCI MODULE

Unspecified 

13.2

WT21-A

Figure 35: Example layout

Do not connect RFTP for WT21-A. See figure 30 for the recommended PCB land pattern. The

impedance matching of the antenna is design for the evaluation board of WT21. For an optimal

performance of the antenna the layout should strictly follow the layout example shown in figure

31 and the thickness of FR4 should be 1,6 mm. Any dielectric material close to the antenna will

change the resonant frequency and it is recommended not to place a plastic case or any other

dielectric closer than 5 mm from the antenna. If this is not possible, or if using other thickness

of FR4 than 1,6 mm, then the antenna can be retuned by removing extra FR4 under the

antenna. Please, contact Bluegiga for the details.

Any metal in close proximity of the antenna will prevent the antenna to radiate freely. It is

recommended not to place any metal closer than 20 mm from the antenna.

Following recommendations helps to avoid EMC problems arising in the design. Note that each

design is unique and the following list do not consider all basic design rules such as avoiding

capacitive coupling between signal lines. Following list is aimed to avoid EMC problems caused

by RF part of the module.

 Do not remove copper from the PCB more than needed. Use ground filling as much as

possible. However remove small floating islands after copper pour.

 Do not place a ground plane underneath the antenna. The grounding areas under the

module should be designed as shown in Figure 31.

 When using overlapping ground areas use conductive vias separated max. 3 mm apart at

the edge of the ground areas. This prevents RF to penetrate inside the PCB. Use ground

vias extensively all over the PCB. All the traces in (and on) the PCB are potential

antennas.

 Avoid loops.

 Ensure that signal lines have return paths as short as possible. With sensitive analog

signals, such as analog audio, use solid ground plane and make sure that the return path

for the signal lines is low impedance and follows the signal lines all the way.

Bluegiga Technologies Oy

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