User`s manual

V1.2 – May-11 User’s Manual Page 26 of 37
8 Use of GPS Antennas
8.1 Connecting a GPS antenna to the GPS receiver
The ANT pin is used to connect a GPS antenna to the receiver. The design of the
antenna connection has to be done strictly according to RF design rules. A 50 Ω PCB
strip line is required. The following drawings shall explain the guidelines. A major rule
is to keep the strip line as short as possible. Additionally, antenna ground (ANT_GND)
should be routed to the ground plane of the PCB (the ground plane is on a lower PCB
layer) by vias as demonstrated in the drawing.
Figure 11: Antenna connector strip line A2100-A/B
In order to achieve the impedance of 50 Ω, the width of the strip line needs to be
calculated. It depends on the thickness or height of the PCB layer (both parameters
are shown in following drawing). For the calculation, it is assumed that the PCB
material is FR4.
Figure 12: Strip line parameters A2100-A/B
Vias to Top Layer
Vias to GND La
y
er
GPS receiver solder pads
50Ωstrip line
Top view
ANT_INT ANT_GND
Motherboard Bottom Layer Motherboard Top Layer
ANT_INT ANT_GND
GPS Receiver
GPS Receiver