Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 System description Page 35 of 157
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  and must be connected to the primary Tx /
Rx antenna through a 50  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 4). Compliance is guaranteed
if the antenna RF interface requirements summarized in Table 7 are fulfilled.
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 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  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.