Final Report of BeJamDetect Project
1OC
M.of-N detection metrics, L1 band
St
300
250
= 200
a.
ant2
ant3
ant4
ant5
ant6
-ant7
Mrashold
50C
50 |
:00
5
400°
350
or
5
M-of-N detection metrics, L1 band
-ant 1
— ant2
ant3
—— ant4
— ant5
ant6
- — ant7
threshold‘
Z
Fol
2X
SO
S{
00 N
500 1000 1500 2000 2500 23000 3500
test block number (each of 1500 samples}
4000
IC
„3 1000 1500 2000 2500 3000 23500 4000
test block number (each of 1500 samples}
a) Nominal case June 01, 2021 at 07:38:21 MET b)RFI case June 01, 2021 at 20:00:31 MET
Figure 3-7: M-of-N detection metric
The main test metric for classifying the potential interference event in the n-th recording is the
increase of the received IF power of the antenna array central (top) element with respect to its
“ominal value:
PıinCn) )
APinasn) = 1010g E(Paınnom)
41)
The received power on the outputs of the RF-front-ends is estimated by using the digital signal
samples. The estimation of the absolute power was not pursued because it would require the
calibration of the entire receiving signal path. Instead, an increase of the received power is
considered to be a manifistation of the presence of an RFl-signal that raises the received power
level in the corresponding frequency band. The nominal power level without interference, i.e. when
only the thermal noise dominates each output of the RF-front-ends, is estimated by using records
without RFI signals detected. The estimation of the nominal power level is further improved by
averaging over many recordings E(Pınnom), e.9. over all snapshots within a given month or longer
time period. This estimation is performed for each array element because the signal gain varies
from one antenna plus RF front-end channel to another. However, only the metric obtained for the
central (top) element of the array was used for the RFl-event categorisation (see Figure 3-8). The
metrics obtained from other array elements were used to estimate the RFI-signal direction of arrival.
Based on the increase of the received power, the RFI events are categorized into three groups as
follows:
RFI strength
\Weak
Medium
Strong
Input power increase
Above 1dB and bellow 3dB
Above 3dB and bellow 5dB
Above 5dB
"able 1 — Radio-frequency interference event strength classification
Title: Final Report
Version: 1.0
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