User's Manual

LE920 Hardware User Guide

1vv0301026 Rev.0 - draft4 – 2013-05-

Antenna Line on PCB Requirements

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 to

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

x Make sure that the transmission line’s characteristic impedance is 50ohm.

x Keep line on the PCB as short as possible since the antenna line loss shall be less than

around 0.3dB.

x Line geometry should have uniform characteristics, constant cross section, avoid

meanders and abrupt curves.

x Any kind of suitable geometry/structure can be used for implementing the printed

transmission line afferent the antenna.

x If a Ground plane is required in line geometry, that plane has to be continuous and

sufficiently extended so the geometry can be as similar as possible to the related

canonical model.

x 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.

x It is wise to surround (on both sides) of the PCB transmission line with Ground. Avoid

having other signal tracks facing directly the antenna line track.

x Avoid crossing any un-shielded transmission line footprint with other tracks on

different layers.

x The Ground surrounding the antenna line on PCB has to 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 line track.

x Place EM noisy devices as far as possible from LE920 antenna line.

x Keep the antenna line far away from the LE920 power supply lines.

x If EM noisy devices are present on the PCB hosting the LE920, such as fast switching

ICs, take care of shielding them with a metal frame cover.

x If EM noisy devices are not present around the line use of geometries like Micro strip

or Grounded Coplanar Waveguide are preferred since they typically ensure less

attenuation when compared to a Strip line having same length.