User's Guide

LE920A4 HW User Guide Antenna(s)
Doc#: 1VV0301261 GSM/WCDMA/TD-SCDMA/LTE Antenna – PCB Line Guidelines
Rev. 4.7.1 Page 63 of 124 2019-11-21
Furthermore, if the device is developed for the US and/or Canada market, it must comply
with the FCC and/or IC approval requirements:
NOTE:
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 module. Antennas used for
this module must not exceed 3dBi gain for mobile and fixed operating
configurations.
GSM/WCDMA/TD-SCDMA/LTE Antenna – PCB Line Guidelines
 Make sure that the transmission line’s characteristic impedance is 50 Ohm.
 Keep the line on the PCB as short as possible since the antenna line loss should
be less than around 0.3 dB.
 Line geometry should have uniform characteristics, constant cross section, and
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, this 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.
 Surround the PCB transmission line with ground (on both sides). Avoid having
other signal tracks facing the antenna line track directly.
 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 the module antenna line.
 Keep the antenna line far away from the module power supply lines.
 If EM-noisy devices are present on the PCB hosting the module, 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, geometries like Micro strip or
Grounded Coplanar Waveguide are preferred because they typically ensure less
attenuation compared to a Strip line having the same length.