LARA-R2 series - System Integration Manual
UBX-16010573 - R12
System description
Page 35 of 157
1.7
Antenna interface
1.7.1
Antenna RF interfaces (ANT1 / ANT2)
LARA-R2 series modules provide two RF interfaces for connecting the external antennas:
The
ANT1
represents the primary RF input/output for transmission and reception of LTE/3G/2G RF signals.
The
ANT1
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 proper RF transmission and reception.
The
ANT2
represents the secondary RF input for the reception of the LTE / 3G RF signals for the Down-Link
Rx diversity radio technology supported by LARA-R2 modules as a required feature for LTE category 1 UEs.
The
ANT2
pin has a nominal characteristic impedance of 50
and must be connected to the secondary Rx
antenna through a 50
transmission line to allow proper RF reception.
1.7.1.1
Antenna RF interface requirements
Table 7, Table 8 and Table 9 summarize the requirements for the antennas RF interfaces (
ANT1
/
ANT2
). See
section 2.4.1 for suggestions to properly design antennas circuits compliant with these requirements.
The antenna circuits affect the RF compliance of the device integrating LARA-R2 series modules
with applicable required certification schemes (for more details see section 4). Compliance is
guaranteed if the antenna RF interfaces (ANT1 / ANT2) requirements summarized in Table 7, Table
8 and Table 9 are fulfilled.
Item
Requirements
Remarks
Impedance
50
nominal characteristic impedance
The impedance of the antenna RF connection must match the 50
impedance of the
ANT1
port.
Frequency Range
See the
LARA-R2 series
Data Sheet
The required frequency range of the antenna connected to the
ANT1
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
ANT1
port.
The impedance of the antenna termination must match as much as
possible the 50
nominal impedance of the
ANT1
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 the antenna input: the efficiency is a measure of how well
an antenna receives or transmits.
The radiation efficiency of the antenna connected to the
ANT1
port
needs to be enough high over the operating frequency range to
comply with the Over-The-Air (OTA) radiated performance
requirements, as the Total Radiated Power (TRP) and the Total Isotropic
Sensitivity (TIS), specified by the 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 the
ANT1
port must
not exceed the herein stated value to comply with regulatory agencies
radiation exposure limits.
For additional info, see sections 4.2.2, 4.3.1 and/or 4.4.
Input Power
> 33 dBm ( > 2 W ) for LARA-R211
> 24 dBm ( > 250 mW ) for other LARA-R2
The antenna connected to the
ANT1
port must support the maximum
power transmitted by the modules with an adequate margin.
Table 7: Summary of primary Tx/Rx antenna RF interface (ANT1) requirements
