SARA-N2 / N3 series - System integration manual
UBX-17005143 - R13
System description
Page 22 of 95
C1-Public
1.7
Antenna interface
1.7.1
Cellular antenna RF interface (ANT)
The
ANT
pin of SARA-N2 / N3 series modules represents the RF input/output for the cellular RF
signals reception and transmission. The
ANT
pin has a nominal characteristic impedance of 50
and
must be connected to the external cellular antenna through a 50
transmission line for proper
reception and transmission of cellular RF signals.
1.7.1.1
Cellular antenna RF interface requirements
summarizes the requirements for the cellular antenna RF interface (
ANT
). See section
for suggestions to properly design an antenna circuit compliant to these requirements.
⚠
The cellular antenna circuit affects the RF compliance of the device integrating SARA-N2 / N3
series module with applicable required certification schemes.
Item
Requirements
Remarks
Impedance
50
nominal characteristic impedance
The nominal characteristic impedance of the
antenna RF connection must match the
ANT
pin
50
impedance.
Frequency range
See the SARA-N2 series data sheet
and
SARA-N3 series data sheet
The required frequency range of the antenna
depends on the operating bands supported by the
cellular module.
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 RF antenna connection matches the 50
impedance.
The impedance of the antenna RF termination must
match as much as possible the 50
impedance of
the
ANT
pin 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 efficiency needs to be enough high over the
operating frequency range to comply with the
Over-The-Air radiated performance requirements,
as Total Radiated Power and Total Isotropic
Sensitivity, specified by certification schemes
Maximum gain
See section
for maximum gain limits
The power gain of an antenna is the radiation
efficiency multiplied by the directivity: the
maximum 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 pin must not exceed the values stated in
section
to comply with regulatory agencies
radiation exposure limits.
Input power
> 0.5 W peak
The antenna connected to ANT pin must support
the maximum power transmitted by the modules.
Table 6: Summary of antenna RF interface (ANT) requirements
☞
For the additional specific requirements applicable to the integration of the SARA-N211 and the
SARA-N310 modules in devices intended for use in potentially explosive atmospheres, see the
guidelines reported in section
