Data Sheet

Table Of Contents

Layout recommendations

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6.2 RF-pads including the diversity port and external antennas

With WGM160P variants without a chip antenna, the important properties are mainly to ensure that WGM160P ground pads are well

connected to PCB ground plane to optimize thermal conductivity and to prevent unwanted emissions due to ground currents.

The RF pads and RF traces conducting the RF signal should be dimensioned to have a characteristic impedance of 50 ohms. It is vital

that proper RF design principles are used when designing an application using the RF pads.

Antennas external to the module, be they connectorized off-the-shelf antennas or PCB trace antennas, must be well matched to 50 ohms.

PCB size and layout recommendations from the antenna manufacturer shall be followed. Board size, ground plane size, plastic enclo-

sures, metal shielding and components in close proximity to the antenna can affect antenna impedance and radiation pattern. There-

fore, antenna matching should be verified in the final enclosure. Better than -10dB return loss throughout the 2.4-2.48 GHz band is rec-

ommended to prevent distortion in the module power amplifier due to impedance mismatch. PA distortion can cause significant packet

loss and poor overall performance.

6.3 Module chip antenna

As is common for very small antennas, the antenna on WGM160P uses the ground plane edge to radiate, rather than just the antenna

chip itself. The antenna on WGM160P is robust to the detuning effect of the proximity of various objects and makes the module easy to

use with a consistent and reliable performance. All the antenna needs is a small patch free from copper under the antenna end of the

module and a solid ground plane covering the whole PCB on at least one layer, especially the edge of the application board where the

antenna is placed. To prevent the RF signal coupling to other, sensitive parts of the design, it is recommended to have a solid, board-

wide ground plane.

For optimal performance of the WGM160P Module, please follow these guidelines:

1. Place the Module at the edge of the PCB with the antenna end flush against the application board edge. If it is necessary to

place the module some distance from the edge, limit the copper plane edges to the level of the module antenna end

2. Place the module close to the center of the edge of the board

3. Do not place any metal (traces, components, battery, etc.) within the clearance area of the antenna

4. Connect all ground pads directly to a solid ground plane covering the whole PCB. The grounds closest to the antenna end

conduct strong RF currents and are critical for good performance, while the rest of the ground pads are important for thermal

conductivity.

5. Place multiple ground vias as close to the ground pads as possible. If possible, fill every unused area in all layers with ground-

connected copper to improve thermal conductivity.

6. Terminate unused RF ports to ground with a resistor between 47 and 51 ohms.

Figure 6.2 Top layer layout of WGM160P reference design