Esd Immunity Test Precautions - u-blox LISA-C2 Series System Integration Manual

The DC impedance at the RF port for some antennas may be a DC open (e.g. linear monopole) or a DC short to
reference GND (e.g. PIFA antenna). For antennas without the diagnostic circuit (shown in Figure 36), the
measured DC resistance will always be at the limits of the measurement range (respectively open or short), and
there will be no means to distinguish between a defect on antenna path with similar characteristics (respectively:
removal of linear antenna or RF cable shorted to GND for PIFA antenna).
Furthermore, any other DC signal injected to the RF connection from ANT connector to radiating element will
alter the measurement and produce invalid results for antenna detection.
It is recommended to use an antenna with a built-in diagnostic resistor in the range of 10 kΩ to 20 kΩ to
assure good antenna detection functionality and to avoid a reduction of module RF performance. The
choke inductor should exhibit a parallel Self Resonance Frequency (SRF) of about 1 GHz to improve the RF
isolation of load resistor.
For example:
Consider a CDMA antenna with built-in DC load resistor of 15 kΩ. Using the +UANTR AT command, the module
reports the resistance value evaluated from ANT connector to GND:
•
Reported values close to the used diagnostic resistor nominal value (i.e. values from 13 kΩ to 17 kΩ if a
15 kΩ diagnostic resistor is used) indicate that the antenna is properly connected
•
Values close to the measurement range maximum limit (approximately 37 kΩ) or an open-circuit
"over range" report (see u-blox LISA-C200 AT Commands Manual [3]) means that that the antenna is not
connected or the RF cable is broken
•
Reported values below the measurement range minimum limit (1 kΩ) will highlight a short to GND at
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 diagnostic
•
Reported values could differ from the real resistance value of the diagnostic resistor mounted inside the
antenna assembly due to antenna cable length, antenna cable capacity and the used measurement method

2.5 ESD immunity test precautions

The immunity of the device (i.e. the application board where the LISA-C200 or FW75-C200 module is mounted)
Electrostatic Discharge must be certified in compliance to the testing requirements standard [13], and the
requirements for radio and digital cellular radio telecommunications system equipment standards [14] and [15].
The ESD test is performed at the enclosure port referred to as the physical boundary through which the EM field
radiates. If the device implements an integral antenna, the enclosure port is seen as all insulating and conductive
surfaces housing the device. If the device implements a removable antenna, the antenna port can be separated
from the enclosure port. The antenna port comprises the antenna element and its interconnecting cable
surfaces.
The applicability of the ESD test depends on the device classification, as well the test on other ports or on
interconnecting cables to auxiliary equipments depends to the device accessible interfaces and manufacturer
requirements.
Contact discharges are performed at conductive surfaces whereas air discharges are performed on insulating
surfaces. Indirect contact discharges are performed on the measurement setup horizontal and vertical coupling
planes.
Implement the following precautions to satisfy ESD immunity test requirements performed at the device
enclosure in compliance to the category level and shown in the following table.
UBX-13000620 - R21
LISA-C2 series and FW75-C200 - System Integration Manual
Early Production Information Design-In
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