Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 System description Page 27 of 119
1.7 Antenna interface
1.7.1 Antenna RF interface (ANT)
SARA-R4/N4 series modules provide an RF interface for connecting the external antenna. The ANT pin represents the
primary RF input/output for transmission and reception of LTE RF signals.
The ANT pin has a nominal characteristic impedance of 50 Ω and must be connected to the primary Tx / Rx antenna
through a 50 Ω transmission line to allow clear RF transmission and reception.
1.7.1.1 Antenna RF interfaces requirements
Table 7 summarizes the requirements for the antenna RF interface. See section 2.4.1 for suggestions to correctly design
antennas circuits compliant with these requirements.
⚠
⚠⚠
⚠ The antenna circuits affect the RF compliance of the device integrating SARA-R4/N4 series modules with applicable
required certification schemes (for more details see section 0). Compliance is guaranteed if the antenna RF interface
requirements summarized in Table 7 are fulfilled.
Item Requirements Remarks
Impedance
50 Ω nominal characteristic impedance
The impedance of the antenna RF connection must match the 50 Ω impedance of
the ANT port.
Frequency Range See the SARA-R4/N4 series Data Sheet [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.
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 Ω characteristic
impedance of the ANT port.
The impedance of the antenna termination must match as much as possible the
50 Ω 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 sections 4.2.2.
Input Power > 24 dBm ( > 0.25 W ) for R404M / R410M
/ N410
> 33 dBm ( > 2.0 W ) for R412M
The antenna connected to the ANT port must support with adequate margin the
maximum power transmitted by the modules.
Table 7: Summary of Tx/Rx antenna RF interface requirements
1.7.2 Antenna detection interface (ANT_DET)
The antenna detection is based on ADC measurement. The ANT_DET pin is an Analog to Digital Converter (ADC) provided
to sense the antenna presence.
The antenna detection function provided by ANT_DET pin is an optional feature that can be implemented if the
application requires it. The antenna detection is forced by the +UANTR AT command. See the SARA-R4/N4 series AT
Commands Manual [2] for more details on this feature.