NEO-D9S - Integration manual
3.4 Antenna supervisor
An active antenna supervisor provides the means to check the antenna for open and short circuits
and to shut off the antenna supply if a short circuit is detected. Once enabled, the active antenna
supervisor produces status messages, reporting in NMEA and/or UBX protocol.
The antenna supervisor can be configured through the CFG-HW-ANT_* configuration items. The
current configuration of the active antenna supervisor can also be checked by polling the related
CFG-HW_ANT_* configuration items.
The current active antenna status can be determined by polling the UBX-MON-RF message. If an
antenna is connected, the initial state after power-up is “Active Antenna OK" in the UBX-MON-RF
message in the u-center "Message View".
An active antenna supervisor circuit is connected to the ANT_DET, ANT_OFF, ANT_SHORT_N
pins. For an example the open circuit detection circuit using ANT_DET, "high" = Antenna detected
(antenna consumes current); "low" = Antenna not detected (no current drawn).
The following schematic details the required circuit and the sections following it explain how to
enable and monitor each feature:
Figure 11: NEO-D9S antenna supervisor
The bias-t inductor must be chosen for multi-band operation; a value of 47 nH ±5% is
required for our recommended Murata part, with the current limited below its 300 mA
rating. See
section for additional information.
Circuit shows buffer [U4]. Buffer is not strictly necessary when supplied from VCC. It is only
required when supplying antenna voltage that is not obtained from or controlled by module
VCC or VCC_RF .
ESD diode not shown in the image above, it is mounted close to the PCB RF connector.
Part
Recommendation
Comment
L1
Murata LQG15HS47NJ02/47N
300mA and >500 Ω at L-band frequencies
UBX-19026111 - R07
3 Receiver functionality
Page 19 of 52
C1-Public