SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08
Objective Specification
Design-in
Page 105 of 188
2.4.2
Antenna detection interface (ANT_DET)
Antenna detection interface (
ANT_DET
) is not supported by SARA-G300 and SARA-G310 modules.
2.4.2.1
Guidelines for ANT_DET circuit design
Figure 52 and Table 26 describe the recommended schematic and components for the antenna detection circuit
to be provided on the application board for the diagnostic circuit that must be provided on the antenna
assembly to achieve antenna detection functionality.
Application Board
Antenna Cable
SARA-G340 / SARA-G350
SARA-U2 series
56
ANT
62
ANT_DET
R1
C1
D1
L1
C2
J1
Z
0
= 50
Ω
Z
0
= 50
Ω
Z
0
= 50 ohm
Antenna Assembly
R2
C4
L3
Radiating
Element
Diagnostic
Circuit
GND
L2
C3
Figure 52: Suggested schematic for antenna detection circuit on application board and diagnostic circuit on antenna assembly
Reference
Description
Part Number - Manufacturer
C1
27 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H270J - Murata
C2
33 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H330J - Murata
D1
Very Low Capacitance ESD Protection
PESD0402-140 - Tyco Electronics
L1
68 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HS68NJ02 - Murata
R1
10 k
Resistor 0402 1% 0.063 W
RK73H1ETTP1002F - KOA Speer
J1
SMA Connector 50
Through Hole Jack
SMA6251A1-3GT50G-50 - Amphenol
C3
SARA:U2: 15 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H150J - Murata
SARA-G3: 0
jumper 0402
Various Manufacturers
L2
SARA:U2: 39 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HN39NJ02 - Murata
SARA-G3: Do not install
C4
22 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H220J - Murata
L3
68 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HS68NJ02 - Murata
R2
15 k
Resistor for Diagnostic
Various Manufacturers
Table 26: Suggested components for antenna detection circuit on application board and diagnostic circuit on antenna assembly
The antenna detection circuit and diagnostic circuit suggested in Figure 52 and Table 26 are here explained:
When antenna detection is forced by the +UANTR AT command, the
ANT_DET
pin generates a DC current
measuring the resistance (R2) from the antenna connector (J1) provided on the application board to GND
DC blocking capacitors are needed at the
ANT
pin (C2) and at the antenna radiating element (C3) to
decouple the DC current generated by the
ANT_DET
pin
Choke inductors with a Self Resonance Frequency (SRF) in the range of 1 GHz are needed in series at the
ANT_DET
pin (L1) and in series at the diagnostic resistor (L2), to avoid a reduction of the RF performance of
the system, improving the RF isolation of the load resistor.
Additional components (R1, C1 and D1 in Figure 52) are needed at the
ANT_DET
pin as ESD protection
