LEXI-R422 - System integration manual
UBX-23007449 - R02
System description
Page 26 of 108
C1-Public
1.7
Antenna interfaces
1.7.1
Cellular antenna RF interface (ANT)
LEXI-R422 modules provide an RF interface for connecting the external cellular antenna. The
ANT
pin
represents the primary RF input/output for transmission and reception of cellular RF signals.
The
ANT
pin has a nominal characteristic impedance of 50
and must be connected to the cellular
Tx / Rx antenna system through a 50
transmission line to allow clear RF transmission and reception.
1.7.1.1
Cellular antenna RF interface requirements
summarizes the requirements for the antenna RF interface. See section
suggestions to correctly design antennas circuits compliant with these requirements.
⚠
The antenna circuits affect the RF compliance of the device integrating LEXI-R422 modules with
applicable required certification schemes (for more details see section
). RF performance is
optimized by fulfilling the cellular antenna RF interface requirements summarized in
Item
Requirements
Remarks
Impedance
50
nominal characteristic impedance The impedance of the antenna RF connection must match the
50
impedance of the
ANT
port.
Frequency range
See the LEXI-R422 data sheet
The required frequency range of the antenna connected to
ANT
port depends on the operating bands of the used cellular module
and the used mobile network.
Return loss
S
11
< -10 dB (VSWR < 2:1)
recommended
S
11
< -6 dB (VSWR < 3:1) acceptable
The return loss or the S
11
, as the VSWR, refers to the amount of
reflected power, measuring how well the antenna RF connection
matches the 50
characteristic impedance of the
ANT
port.
The impedance of the antenna termination must match as much
as possible the 50
nominal impedance of the
ANT
port over the
operating frequency range, reducing as much as possible the
amount of reflected power.
Efficiency
> -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
The radiation efficiency is the ratio of the radiated power to the
power delivered to antenna input: the efficiency is a measure of
how well an antenna receives or transmits.
The radiation efficiency of the antenna connected to the
ANT
port
needs to be enough high over the operating frequency range to
comply with the Over-The-Air (OTA) radiated performance
requirements, as Total Radiated Power (TRP) and the Total
Isotropic Sensitivity (TIS), specified by applicable related
certification schemes.
Maximum gain
According to radiation exposure limits The power gain of an antenna is the radiation efficiency multiplied
by the directivity: the gain describes how much power is
transmitted in the direction of peak radiation to that of an
isotropic source.
The maximum gain of the antenna connected to
ANT
port must
not exceed the herein stated value to comply with regulatory
agencies radiation exposure limits. For additional info see
section
Input power
> 33 dBm ( > 2.0 W )
The antenna connected to the
ANT
port must support with
adequate margin the maximum power transmitted by the
modules.
Table 7: Tx/Rx antenna RF interface requirements
