Sierra Wireless AirPrime SL808 Series Product Technical Specification & Customer Design Manuallines page 99

Figure 8-3: AppCad screenshot for MicroStrip design
If a multi-layered PCB is used, the RF path on the board must not cross any
signal (digital, analog or supply).
If necessary, use StripLine structure and route the digital line(s) "outside" the RF
structure as shown in the figure below.

50 line
LGA pin for ANT
Figure 8-4: Routing examples
Stripline and Coplanar design requires having a correct ground plane at both
sides. Consequently, it is necessary to add some vias along the RF path.
It is recommended to use Stripline design if the RF path is fairly long (more than
3cm), since MicroStrip design is not shielded. Consequently, the RF signal (when
transmitting) may interfere with neighboring electronics (AF amplifier, etc.). In the
same way, the neighboring electronics (micro-controllers, etc.) may degrade the
reception performances.
Rev 1 Dec.10 Proprietary and Confidential - Specifications subject to change 99