User's Guide

LE910Cx HW User Guide
Doc#: 1VV0301298
Rev. 13.0 Page 64 of 124 2019-07-15
7.5.2. Linear and Patch GNSS Antenna
Using this type of antenna introduces at least 3 dB of loss compared to a circularly
polarized (CP) antenna. Having a spherical gain response instead of a hemispherical gain
response can aggravate the multipath behaviour and create poor position accuracy.
7.5.3. Front End Design Considerations
Since there is no antenna connector on the LE910Cx module, the antenna must be
connected to the LE910Cx through the PCB to the antenna pad.
If the antenna is not directly connected at the antenna pad of the LE910Cx, a PCB line is
required.
This line of transmission must meet the following requirements:
Table 22: Antenna Line on PCB Requirements
Characteristic impedance
50 Ohm
Max attenuation
0.3 dB
Avoid coupling with other signals.
Cold End (Ground Plane) of the antenna must be equipotential to the LE910Cx ground
pads.
Furthermore, if the device is developed for the US and/or Canada market, it must comply
with the FCC and/or IC requirements.
This device is to be used only for mobile and fixed application.
7.5.4. GNSS Antenna – PCB Line Guidelines
• Ensure that the antenna line impedance is 50 Ohm.
• Keep the line on the PCB as short as possible to reduce the loss.
• The antenna line must have uniform characteristics, constant cross section,
avoiding meanders and abrupt curves.
• Keep one layer of the PCB used only for the Ground plane; if possible.
• Surround (on the sides, over and under) the antenna line on the PCB with Ground.
Avoid having other signal tracks directly facing the antenna line track.
• The Ground around the antenna line on the PCB must be strictly connected to the
main Ground plane by placing vias at least once per 2mm.
• Place EM-noisy devices as far as possible from LE910Cx antenna line.
• Keep the antenna line far away from the LE910Cx power supply lines.
• If EM-noisy devices are around the PCB hosting the LE910Cx, such as fast
switching ICs, ensure shielding the antenna line by burying it inside the layers of
PCB and surrounding it with Ground planes; or shield it with a metal frame cover.
• If you do not have EM-noisy devices around the PCB of LE910Cx, use a Micro
strip line on the surface copper layer for the antenna line. The line attenuation will
be lower than a buried one.