Specifications

Table Of Contents
Cinterion
®
ALAS5V Hardware Interface Description
2.2 GSM/UMTS/LTE Antenna Interface
67
ALAS5V_HID_v00.030a 2019-03-20
Confidential / Preliminary
Page 53 of 124
2.2.4 RF Antenna Diagnostic
RF antenna (GSM/UMTS/LTE) diagnosis requires the implementation of an external antenna
detection circuit. An example for such a circuit is illustrated in Figure 21. It allows to check the
presence and the connection status of RF antennas.
To properly detect the antenna and verify its connection status the antenna feed point must
have a DC resistance R
ANT
of 9k (±3k).
A positive or negative voltage drop (referred to as V
disturb
) on the ground line may occur without
having any impact on the measuring procedure and the measuring result. A peak deviation
(V
disturb
) of < 0.8V from ground is acceptable.
V
disturb
(peak) = ± 0.8V (maximum); f
disturb
= 0Hz … 5kHz
Waveform: DC, sinus, square-pulse, peak-pulse (width = 100µs)
R
disturb
= 5
To make sure that the antenna detection operates reliably, the capacitance at the module’s an-
tenna pad (i.e., the cable capacitance plus the antenna capacitance (C
ANT
)) should not be
greater than 1000pF. Some types of antennas (for example "inverted F antenna" or "half loop
antenna") need an RF short circuit between the antenna structure and ground to work properly.
In this case the RF short circuit has to be realized via a capacitance (C
ANT
) . For C
ANT
we rec-
ommend a capacitance lower than 100pF (see Figure 20).
Figure 20: Resistor measurement used for antenna detection
~
Antenna
RA
SC1 SC2
8...36V
-0.8V...+0.8V
0...5kHz
1.6Vpp
Ri=5Ohm
6k...12k
ANT