CHAPTER 7. RECE
I
VER MON
I
TOR
I
NG
7 Receiver Monitoring
7.1 AIM+: Using the spectrum analyser to
detect and mitigate interference
The AsteRx SB Sx is equipped with a sophisticated RF interference monitoring and mitigation
system (A
I
M+). To mitigate the e
ff
ects of narrow-band interference, 3 notch
fi
lters can be
con
fi
gured either in auto or manual mode. These notch
fi
lters e
ff
ectively remove a narrow
part of the RF spectrum around the interfering signal. The L2 band being open for use by
radio amateurs is particularly vulnerable to this type of interference. The e
ff
ects of wideband
interference both intentional and unintentional can be mitigated by turning on the WB
I
mitigation system. The WB
I
system also reduces, more e
ff
ectively than traditionally used
pulse-blanking methods, the e
ff
ects of pulsed interferers.
The spectrum view plot
I
n the Spectrum window of the GNSS menu, you can monitor the RF spectrum and con
fi
gure
three separate notch
fi
lters to cancel out narrowband interference. Figure 7-1 shows the L2
frequency band with the GPS L2P signal at 1227.60 indicated. Di
ff
erent bands can be viewed
by clicking on the
‘
Show table
’
button as shown. The spectrum is computed from baseband
samples taken at the output of the receiver
’
s analog to digital converters.
Figure 7-1:
The RF spectrum of the L2 Band
47