Page 23 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum
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ITU Journal: ICT Discoveries, Vol. 2(1), December 2019
the L1-band was severely affected, depending on
Antenna the receiver’s type and on the bandwidth of the
antenna used. GPS-only stations were not affected,
because the related antenna bandwidth is sharp
enough around L1 carrier frequency to reject the
Low Noise Amplifier jamming signal.
Changes in the jamming signal power were
observed over time, according to some provisional
Power Divider monitoring. The potential implementation of a low-
noise active microwave diplexer is under study. In
addition, future plans are to implement a more
Band-pass Filter consistent dedicated observation of the jamming
L2/L5/E5a/E5b signal, and more generally of the frequency
spectrum around all the GNSS frequency bands. To
Band-pass Filter develop our knowledge in this field appears
L1/E1 mandatory today for all future GNSS activities
according to the laboratory time metrology
missions.
Power Combiner
ACKNOWLEDGEMENT
We acknowledge the Agence Nationale des
Attenuator Fréquences (ANFR) for the help in trying to solve
the issue.
REFERENCES
Receiver Main Unit
Indoor [1] M. Abgrall, B. Chupin, L. De Sarlo, J. Guéna, Ph.
Laurent, Y. Le Coq, R. Le Targat, J. Lodewyck,
M. Lours, P. Rosenbusch, G.D. Rovera, S. Bize
Fig. 12 – Block diagram of the low-noise active microwave (2015). Atomic Fountains and optical clocks
diplexer aiming at filtering out the jamming signal
at SYRTE: Status and perspectives, Comptes
Rendus Physique, Vol.16, Issue 5, June 2015,
9. CONCLUSION
461-470.
For fulfilling its time and frequency metrology [2] G.D. Rovera, S. Bize, B. Chupin, J. Guéna,
missions, LNE-SYRTE is operating an ensemble of Ph. Laurent, P. Rosenbusch, P. Uhrich and
calibrated GNSS stations in OP aiming at accurate M. Abgrall (2016). UTC(OP) based on
time transfer between remote atomic standards. LNE-SYRTE atomic fountain primary
But since November 2018, a powerful signal frequency standards, Metrologia 53 S81.
occupying a frequency band just below the L1
frequency band allocated to GNSS signals has [3] BIPM (2019). 2018 Group 1 GPS calibration
appeared. Its signal power level is indicating a trip (Cal_Id 1001-2018), v1.4 / 20190327.
ground source near to OP. This is apparently not in https://www.bipm.org/utils/common/Time
line with ITU frequency tables, where this Calibrations/Current/1001-
frequency band is allocated to space to Earth 2018_GPSP3C1_Group1-trip_V1-4.pdf
satellite telecommunications. The signal is jamming [4] IGS Central Bureau (2019).
OP stations’ reception when using large bandwidth http://www.igs.org/igsnetwork/network_by
multi-GNSS antennas and receivers. A formal _site.php?site=opmt00fra
complaint was raised to ANFR in early 2019.
[5] IGS Central Bureau (2019).
The impact of this jamming signal was observed in http://www.igs.org/igsnetwork/network_by
different ways. First, a sudden loss of some GNSS _site.php?site=op7100fra
data, together with an increase of noise, was
detected, leading to unexpected large offsets
between calibrated OP stations. Second, the C/N0 in
© International Telecommunication Union, 2019 7
