LEA-M8F - Hardware Integration Manual
UBX-14000034 - R03
Early Production
Information
Design
Page 15 of 30
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In order to avoid reliability hazards, the area on the PCB under the receiver should be entirely covered with
solder mask. Vias should not be open. Do not route under the receiver.
2.1.3
Antenna micro strip connection
There are many ways to design wave-guides on printed circuit boards. Common to all is that calculation of the
electrical parameters is not straightforward. Freeware tools like AppCAD from Avago Technologies or TXLine
from Applied Wave Research, Inc. are of great help. They can be downloaded from
http://www.avagotech.com/pages/appcad
or http://www.hp.woodshot.com/ and
The micro strip is the most common RF interconnect configuration for printed circuit boards. The basic
configuration is shown in Figure 10
and Figure 11. As a rule of thumb, for an FR-4 material the width of the
conductor is roughly double the thickness of the dielectric to achieve 50
Ω
line impedance.
For the correct calculation of the micro strip impedance, not only must one consider the distance between the
top and the first inner layer, but also the distance between the micro strip and the adjacent GND plane on the
same layer.
Use the Coplanar Waveguide model for the calculation of the micro strip dimensions.
Figure 10: Micro strip on a 2-layer board (Agilent AppCAD Coplanar Waveguide)
Figure 10 shows an example of a 2-layer FR4 board with 1.6 mm thickness and a 35 µm (1 ounce) copper
cladding. The thickness of the micro strip is comprised of the cladding (35 µm) plus the plated copper (typically
25 µm). Figure 11 is an example of a multi layer FR4 board with 18 µm (½ ounce) cladding and 180 µ dielectric
between layer 1 and 2.
