Sierra Wireless AIRPRIME WISMO218 - Manual (Page 88)

WA_DEV_W218_PTS_002 Rev 006 April 29, 2010 88
Product Technical Specification &
Customer Design Guidelines Technical Specifications
5.3. PCB Specification for Application Board
In order to save costs for simple applications, a cheap PCB structure can be used for the application
board of the AirPrime WISMO218. A 4-layer through-hole type PCB structure can be used.
Figure 44. PCB Structure Example for the Application Board
Due to the limited layers of 4-layer PCBs, sensitive signals like audio, SIM and clocks cannot be
protected by 2 adjacent ground layers. As a result, during PCB layout, care must be taken for these
sensitive signals, by avoiding coupling to noisy baseband through adjacent layers.