Ublox SARA-N210, System Integration Manual

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SARA-N2 series - System Integration Manual
UBX-17005143 - R06 Design-in Page 40 of 82
2.4.2 Antenna detection interface (ANT_DET)
☞
Antenna detection interface is not supported in the "02" version of the product.
2.4.2.1 Guidelines for ANT_DET circuit design
Figure 19 and Table 18 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-N2 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
R
2
C4
L3
Radiating
Element
Diagnostic
Circuit
GND
L2
C3
Figure 19: 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 15 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H150J - Murata
L2 39 nH Multilayer Inductor 0402 (SRF ~1 GHz) LQG15HN39NJ02 - Murata
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 18: 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 19 and Table 18 are here
explained:
 When antenna detection is forced by the dedicated AT command (see SARA-N2 series AT
Commands Manual
[3] ), 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 (C4)
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 (L3), 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 19 ) are needed at the ANT_DET pin as ESD
protection.