8 Use of External Antenna
8.1 Connection of RF Signal
The ANT_EXT pin is used to connect the receiver with the GPS antenna. The de-
sign 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 guide-
lines. A major rule is to keep the strip line as short as possible. Additionally, an-
tenna 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 12: Antenna connector strip line A1035-H
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 ma-
terial is FR4.
Figure 13: Strip line parameters A1035-H
In this case, the width should be about 1.8 times the height of the PCB:
W = 1.8 x H
In the example, one would get a width of W = 1.8 x 0.8 mm = 1.44 mm.
V1.5 – Dec-09
User’s Manual
Page 24 of 37
