Lantronix A5135-H, User Manual, Page: 26 / 33

GNSS Receiver Module A5135-H User Guide 26
8 Use of External Antenna
8.1 Connection of RF Signal
The ANT_EXT pin is used to connect the receiver with the GNSS antenna. The de-
sign of the antenna connection must be strictly done according to RF design rules.
Following drawings explain the guidelines:
- the main rule is to keep the strip line as short as possible.
- 50 Ω PCB strip line is required.
- the strip line needs a good reference ground.
Figure 14: Antenna connector strip line A5135-H
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 15: Strip line parameters A5135-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, you would get a width of W = 1.8 x 0.8 mm = 1.44 mm.