SARA-N2 / N3 series - System integration manual
UBX-17005143 - R13
Product testing
Page 89 of 95
C1-Public
Dedicated tests can be implemented to check the device. For example, AT commands can be used to
perform functional tests on the digital interfaces (communication with the host controller, check the
SIM interface, GPIOs, etc.) or to perform RF functional tests (see following section
for details).
5.2.1
“Go/No go” tests for integrated devices
A “Go/No go” test is typically used to compare the signal quality with a “Golden Device” in a location
with excellent network coverage and known signal quality. This test should be performed after the
data connection has been established. AT+CSQ is the typical AT command used to check signal
quality in term of Received Signal Strength Indication (RSSI). See the SARA-N2 / N3 series AT
commands manual
for the AT+CSQ command syntax description and usage.
☞
These kinds of test may be useful as a “go/no go” test but not for RF performance measurements.
This test is suitable to check the functionality of communications with the host controller, the SIM
card and the power supply. It is also a means to verify if components at the antenna interface are well-
soldered.
5.2.2
RF functional tests
As mentioned above, OEM manufacturers need only to verify proper assembly of the module in the
OEM production line, i.e. proper soldering joint of the
ANT
pad and related parts along the RF path,
and this can be done by performing a simple RF functional test with basic instruments such as a
spectrum analyzer (or an RF power meter), and optionally a signal generator, with the assistance of
the +UTEST AT command over the AT command user interface.
The AT+UTEST command provides a simple interface to set the SARA-N2 / N3 series modules to Rx
or Tx test modes ignoring the cellular signaling protocol. The command can set the module into:
•
transmitting mode in a specified channel and power level in all supported bands
•
receiving mode in a specified channel to return the measured power level in supported bands
This feature allows the measurement of the transmitter and receiver power levels to check the
component assembly related to the module antenna interface and to check other device interfaces
on which the RF performance depends.
The minimum recommended RF verification in production consists in forcing the module to transmit
in a supported frequency the +UTEST AT command, and then checking that some power is emitted
from the antenna system using any suitable power detector, power meter or equivalent equipment.
☞
See the SARA-N2 / N3 series AT commands manual
and the SARA-N3 application development
for the detailed description of the +UTEST AT command.
⚠
To avoid module damage during a transmitter test, a suitable antenna according to module
specifications or a 50
termination must be connected to the
ANT
port.
⚠
To avoid module damage during a receiver test, the maximum power level received at the
ANT
port
must meet module specifications.
☞
The AT+UTEST command sets the module to emit RF power ignoring cellular signaling protocol.
This emission can generate interference that can be prohibited by law in some countries. The use
of this feature is intended for testing purposes in controlled environments by qualified users and
must not be used during the normal module operation. Follow the instructions suggested in the
u-blox documentation. u-blox assumes no responsibilities for the inappropriate use of this feature.
