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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
Table 7
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 4). RF performance is
optimized by fulfilling the cellular antenna RF interface requirements summarized in
Item
Requirements
Impedance
50 nominal characteristic impedance The impedance of the antenna RF connection must match the
Frequency range See the LEXI-R422 data sheet
Return loss
S
< -10 dB (VSWR < 2:1)
11
recommended
S
< -6 dB (VSWR < 3:1) acceptable
11
Efficiency
> -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
Maximum gain
According to radiation exposure limits
Input power
> 33 dBm ( > 2.0 W )
Table 7: Tx/Rx antenna RF interface requirements
UBX-23007449 - R02
C1-Public
LEXI-R422 - System integration manual
Remarks
50 impedance of the ANT port.
[1]
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.
The return loss or the S
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.
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.
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 4.
The antenna connected to the ANT port must support with
adequate margin the maximum power transmitted by the
modules.
System description
, as the VSWR, refers to the amount of
11
Page 26 of 108
2.4.1.4
for
Table
7.
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