User's Guide

LE866 HARDWARE USER GUIDE 1vv0301210 Rev.0 Preliminary 2015-09-02 47 of 68
Reproduction forbidden without Telit Communications PLC written authorization All Rights Reserved
RX Diversity Antenna
This product is including an input for a second RX antenna to improve the data throughput.
The function is called Antenna Diversity (downlink MIMO) in LTE.
The second Rx antenna should not be located in the close vicinity of main antenna. In order to improve
Diversity Gain, Isolation and reduce mutual interaction, the two antennas should be located at the
maximum reciprocal distance possible, taking into consideration the available space into the application.
For the same reason, the Rx antenna should also be cross-polarized with respect to the main antenna.
Isolation between main antenna and Rx antenna must be at least 10 dB in all uplink frequency bands.
Envelope Correlation Coefficient (ECC) value should be as close as possible to zero, for best diversity
performance. ECC values below 0.5 on all frequency bands are recommended.
PCB design guidelines
When using the LE866, since there's no antenna connector on the module, the antenna must be
connected to the LE866 antenna pad by means of a transmission line implemented on the PCB.
In the case the antenna is not directly connected at the antenna pad of the LE866, then a PCB line is
needed in order to connect with it or with its connector.
This transmission line shall fulfil the following requirements:
The transmission line should be designed according to the following guidelines:
Item
Value
Frequency range
Depending by frequency band(s) provided by the network
operator, the customer shall use the most suitable antenna for
that/those band(s)
Bandwidth
LTE Band IV(1700) : 45 MHz
LTE Band XIII(700) : 10 MHz
Impedance
50 ohm
VSWR recommended
≤ 2:1 (recommended for the best sensitivity performance)
Item
Value
Characteristic Impedance
50 ohm
Max Attenuation
0,3 dB
Coupling
Coupling with other signals shall be avoided
Ground Plane
Cold End (Ground Plane) of antenna shall be equipotential to
the LE866 ground pins