User's Manual

LE920 Hardware User Guide
1vv0301026 Rev.8 2015-01-03
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 46 of 88
Characteristic Impedance
50Ohm
Max Attenuation
0.3dB
Coupling with other signals shall be avoided
Cold End (Ground Plane) of antenna shall be equipotential to the LE920 ground pads
Furthermore if the device is developed for the US and/or Canada market, it must comply with
the FCC and/or IC approval requirements:
This device is to be used only for mobile and fixed application. The antenna(s) used for this
transmitter must be installed to provide a separation distance of at least 20 cm from all
persons and must not be co-located or operating in conjunction with any other antenna or
transmitter. End-Users must be provided with transmitter operation conditions for satisfying
RF exposure compliance. OEM integrators must ensure that the end user has no manual
instructions to remove or install the LE920 module. Antennas used for this OEM module must
not exceed 3dBi gain for mobile and fixed operating configurations.
6.2. GSM/WCDMA/LTE Antenna – PCB line Guidelines
 Make sure that the transmission line’s characteristic impedance is 50ohm.
 Keep the line on the PCB as short as possible since the antenna line loss should be less
than around 0.3dB.
 Line geometry should have uniform characteristics, constant cross section, avoid
meanders and abrupt curves.
 Any suitable geometry/structure can be used for implementing the printed transmission
line affecting the antenna.
 If a Ground plane is required in the line geometry, that plane must be continuous and
sufficiently extended so the geometry can be as similar as possible to the related canonical
model.
 Keep, if possible, at least one layer of the PCB used only for the Ground plane; if possible,
use this layer as reference Ground plane for the transmission line.
 It is wise to surround (on both sides) the PCB transmission line with Ground. Avoid
having other signal tracks facing directly the antenna line track.
 Avoid crossing any un-shielded transmission line footprint with other tracks on different
layers.
 The Ground surrounding the antenna line on the PCB must be strictly connected to the
main Ground plane by means of via-holes (once per 2mm at least) placed close to the
ground edges facing the line track.
 Place EM-noisy devices as far as possible from LE920 antenna line.
 Keep the antenna line far away from the LE920 power supply lines.
 If EM-noisy devices are present on the PCB hosting the LE920, such as fast switching
ICs, take care to shield them with a metal frame cover.
 If EM-noisy devices are not present around the line, using geometries like Micro strip or
Grounded Coplanar Waveguide is preferred since they typically ensure less attenuation
compared to a Strip line having the same length.