Integration Manual

TSD-19090601 - R15 Contents Page 86 of 143
2.4.2 Antenna detection interface (ANT_DET)
2.4.2.1 Guidelines for ANT_DET circuit design
Figure 23 and Table 29 describe the recommended schematic / components for the antennas detection
circuit that must be provided on the application board and for the diagnostic circuit that must be provided
on the antennas’ assembly to achieve primary and secondary antenna detection functionality.
Application Board
Antenna Cable
TOBY-L3 series
81
ANT1
75
ANT_DET
R1
C1 D1
C2
J1
Z
0
= 50 Ohm Z
0
= 50 Ohm
Z
0
= 50 Ohm
Primary Antenna Assembly
R2
C4
L3
Radiating
Element
Diagnostic
Circuit
L2
L1
Antenna Cable
87
ANT2
C3
J2
Z
0
= 50 Ohm Z
0
= 50 Ohm
Z
0
= 50 Ohm
Secondary Antenna Assembly
R3
C5
L4
Radiating
Element
Diagnostic
Circuit
Figure 23: Schematic example for antenna detection circuit on application PCB and diagnostic circuit on antennas assembly
Reference
Description
Part Number - Manufacturer
C1
27 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H270J - Murata
C2, C3
33 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H330J - Murata
D1
Very Low Capacitance ESD Protection
PESD0402-140 - Tyco Electronics
L1, L2
68 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HS68NJ02 - Murata
R1
10 k Resistor 0402 1% 0.063 W
RK73H1ETTP1002F - KOA Speer
J1, J2
SMA Connector 50  Through Hole Jack
SMA6251A1-3GT50G-50 - Amphenol
C4, C5
22 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H220J - Murata
L3, L4
68 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HS68NJ02 - Murata
R2, R3
15 k Resistor for Diagnostic
Various Manufacturers
Table 29: Example of parts for antenna detection circuit on application PCB and diagnostic circuit on antennas assembly
The antenna detection circuit and diagnostic circuit suggested in Figure 23 and Table 29 are explained here:
 When antenna detection is forced by the AT+UANTR command, ANT_DET generates a DC current
measuring the resistance (R2 // R3) from the antenna connectors (J1, J2) provided on the application
board to GND.
 DC blocking capacitors are needed at the ANT1 / ANT2 pins (C2, C3) and at the antenna radiating
element (C4, C5) 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, L2) and in series at the diagnostic resistor (L3, L4), to avoid a reduction of the RF
performance of the system, improving the RF isolation of the load resistor.