Tyco Electronics A1082-A, Руководство пользователя

Страница: 21 / 27

GPS receiver A1082-A
8 Use of Antenna
8.1 Connection of RF Signal
The ANT pin is used to connect the receiver with the GPS antenna. 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
(GNDANT) should be routed to the ground plane of the PCB (the ground plane is
on a lower PCB layer) by via as demonstrated in the drawing.
Motherboard GND layer Motherboard top layer
GPS module
RF
in RF
GND
RF
GND
GPS module
RF
in RF
GND
RF
GND
Figure 10: Antenna connector strip line A1082-A
In order to gain the impedance of 50
Ω
, the width of the strip line needs to be calcu-
lated. 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 mate-
rial is FR4.
Figure 81: Strip line parameters A1082-A
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 0.8mm = 1.44mm.
50 Ω strip line
Vias to Top Layer
Vias to GND Layer
BGA Solder pads
V1.0 - 10/07 User’s Manual Page 21 of 27