LENA-R8 series - System integration manual
UBX-22015376 - R02
Design-in
Page 66 of 116
C1-Public
For example:
Consider an antenna with a built-in DC load resistor of 15 k
. Using the +UANTR AT command, the
module reports the resistance value evaluated from the antenna connector provided on the
application board to GND:
•
Reported values close to the used diagnostic resistor nominal value (i.e. values from 13 k
to 17 k
if a 15 k
diagnostic resistor is used) indicate that the antenna is properly connected.
•
Values close to the measurement range maximum limit (approximately 50 k
) or an open-circuit
“over
range” report (see the AT
) means that that the antenna is not
connected or the RF cable is broken.
•
Reported values below the measurement range minimum limit (1 k
) highlights a short to GND at
the antenna or along the RF cable.
•
Measurement inside the valid measurement range and outside the expected range may indicate
an improper connection, damaged antenna or wrong value of antenna load resistor for diagnostics.
•
The reported value could differ from the real resistance value of the diagnostic resistor mounted
inside the antenna assembly due to antenna cable length, antenna cable capacity or the
measurement method used.
☞
If the antenna detection function is not required by the customer application, the
ANT_DET
pin
can be left unconnected and the
ANT
pin can be directly connected to the related antenna
connector by a 50
transmission line as described in
2.4.5.2
Guidelines for ANT_DET layout design
The recommended layout for the primary antenna detection circuit to be provided on the application
board to achieve the primary antenna detection functionality, implementing the recommended
schematic described in
, is explained here:
•
The
ANT
pin must be connected to the antenna connector by a 50
transmission line,
implementing the design guidelines described in section
and the recommendations of the
SMA connector manufacturer.
•
DC blocking capacitor at
ANT
pin (C2) must be placed in series to the 50
RF line.
•
The
ANT_DET
pin must be connected to the 50
transmission line by means of a sense line.
•
Choke inductors in series at the
ANT_DET
pin (L1) must be placed so that one pad is on the 50
transmission line and the other pad represents the start of the sense line to
ANT_DET
pin.
•
The additional components (R1, C1, D1) on the
ANT_DET
line must be placed as ESD protection.
2.4.6
Cellular antenna dynamic tuning interface (RFCTRL1 / RFCTRL2)
☞
Cellular antenna dynamic tuner interface support is planned for future firmware versions.
shows the example application circuits implementing impedance tuning and aperture
tuning. The module controls an RF switch, which selects the right matching element for the operating
band.
contains suggested components implementing the SP4T RF switch functionality.