User's Manual

Bluegiga Technologies Oy
Page 12 of 52
5 Layout Guide Lines
Use good layout practices to avoid excessive noise coupling to supply voltage traces or sensitive analog
signal traces. If using overlapping ground planes use stitching vias separated by max 3 mm to avoid emission
from the edges of the PCB. Connect all the GND pins directly to a solid GND plane and make sure that there
is a low impedance path for the return current following the signal and supply traces all the way from start to
the end.
A good practice is to dedicate one of the inner layers to a solid GND plane and one of the inner layers to
supply voltage planes and traces and route all the signals on top and bottom layers of the PCB. This
arrangement will make sure that any return current follows the forward current as close as possible and any
loops are minimized.
Signals
GND
Power
Signals
Figure 5: Typical 4-layer PCB construction
Overlapping GND layers without
GND stitching vias
Overlapping GND layers with
GND stitching vias shielding the
RF energy
Figure 6: Use of stitching vias to avoid emissions from the edges of the PCB
5.1 BT111-A Layout Guide
For optimal performance of the antenna place the module at the corner of the PCB of the mother board as
shown in the figure 7. Optionally the module can be placed on the long edge of the mother board. In this case
the metal clearance area must be extended minimum 10mm from the edge of the module, as shown in figure
7. The layout of the mother board has an impact on the antenna characteristic and radiation pattern, see the
antenna characteristics chapter. Do not place any metal (traces, components, battery etc.) within the
clearance area of the antenna. Connect all the GND pins directly to a solid GND plane. Place the GND vias as
close to the GND pins as possible. Use good layout practices to avoid any excessive noise coupling to signal
lines or supply voltage lines. Avoid placing plastic or any other dielectric material closer than 5 mm from the
antenna. Any dielectric closer than 5 mm from the antenna will detune the antenna to lower frequencies.
The antenna is optimized for mother board thickness of 1.0 mm. If the mother board is thicker than this, the
resonant frequency will be tuned downwards. If the mother board thickness is thinner than 1.0 mm, the