LENA-R8 series - System integration manual
UBX-22015376 - R02
System description
Page 24 of 116
C1-Public
1.8.1.1
Cellular antenna RF interface requirements
summarizes the requirements for the RF interface (
ANT
). See section
to properly design the circuits compliant with these requirements.
⚠
The antenna circuits affect the RF compliance of the host end-device integrating the LENA-R8
series modules with applicable required certification schemes (for further details see section
RF performance is optimized by fulfilling the requirements summarized in
Item
Requirement
Remark
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 LENA-R8 series data
sheet
The required frequency range of the antenna connected to the
ANT
port
depends on the operating bands of the used cellular module and the used
mobile network.
Return Loss
S11 < -10 dB (VSWR < 2:1)
recommended
S11 < -6 dB (VSWR < 3:1)
acceptable
The Return loss or the S11, 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 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
ANT
port needs
to be high enough 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
ANT
port must not
exceed the herein stated value to comply with regulatory agencies
radiation exposure limits.
For additional info, see sections
and/or
Input Power
> 33 dBm (> 2.0 W)
The antenna connected to the
ANT
port must support the maximum
power transmitted by the modules with an adequate margin.
Table 6: Summary of primary Tx/Rx antenna RF interface (ANT1) requirements
1.8.2
Cellular antenna detection (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 the
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 u-blox AT commands manual
for more details on this feature.
The
ANT_DET
pin generates a DC current (for detailed characteristics, see the LENA-R8 series data
sheet
) and measures the resulting DC voltage, thus determining the resistance from the antenna
connector provided on the application board to GND. The requirements to achieve antenna detection
functionality areas follows:
•
an RF antenna assembly with a built-in resistor (diagnostic circuit) must be used
•
an antenna detection circuit must be implemented on the application board
See section
for the antenna detection circuit on the application board and the diagnostic circuit
on the antenna assembly design-in guidelines.
