Resolution 606

Interference from RNSS to radars in the 1215 – 1300 MHz band

Philippe GERARDAgence Nationale des Fréquences

Gerard@anfr.frMars 2001

AMCP WGF/6-WP/39

Resolution 606 : protection of radars in 1215 –1300 MHz band

L2 L1

1215 MH

z

1260 MH

z

1559 MH

z

1610 MH

z

L5/E5 1300 M

Hz

E6

5010 MH

z

5030 MH

z

C

Protection of radiolocationresolution 606

L2 L1

1164 MH

z

L5/E5 C

Sharing between RNSS and ARNS

resolution 605

Protection of radiolocationresolution 607

Protection of MLSresolution 603

Protection of radioastronomyresolution 604

Sharing with MIDS

Compatibility with MSS

OOB emissions from radars

RES 606 [COM5/20]

consideringa) that this conference has decided to introduce a new allocation for the

radionavigation-satellite service (space-to-Earth) in the frequency band 1 260-1 300 MHz;

b) that in the band 1 215-1 260 MHz radionavigation-satellite service (space-to-Earth) systems have been successfully operated for a considerable time in a band used by radars;

c) the importance of the radionavigation service authorized in certain countries in accordance with No. S5.331 and of the radiolocation service, and the need for adequate protection and continued operation of these services throughout the band 1 215-1 300 MHz,

RES 606 [COM5/20]

resolves

1 that no additional constraints shall be placed on radionavigation-satellite service (space-to-Earth) systems operating in the band 1 215-1 260 MHz;

2 to recommend that WRC-03 review the results of the studies in invites ITU-R and take appropriate action,

RES 606 [COM5/20]

invites ITU-Rto conduct, as a matter of urgency and in time for WRC-03, the appropriate technical, operational and regulatory studies, including an assessment of the need for a power flux-density limit concerning the operation of radionavigation-satellite service (space-to-Earth) systems in thefrequency band 1 215-1 300 MHz in order to ensure that the radionavigation-satellite service (space-to-Earth) will not cause harmful interference to the radionavigation and the radiolocationservices,

instructs the Secretary-Generalto communicate the contents of this resolution to ICAO for such actions as

it may consider appropriate and to invite ICAO to participate actively in the study activity identified under invites ITU-R.

Resolution 606

ITU-R Last WP 8D : October 2000Next WP 8D : end of May 2001

CEPT Last SE 28 : January 2001Next SE 28 : 2 May 2001 (to prepare next WP 8D)

Resolution 606 :

last WP 8D : calculation of pfd for GPS and GLONASS(doc 8D/18 E)

CEPT proposed :Pfd limit of -133 dBW/m2/1MHz

(GALILEO : E6,40 MHz, -155 dBW -134 dBW/ m2 /1MHz)

A –167 dBW Minimum received power level

for Glonass C/A in L2 M.1317

B –23.7 dBm² Effective area of 0 dBi antenna C –143.3 dBW/m² Minimum pfd level for 1 satellite C=A-B D 10 dB Maximum/minimum pfd ratio (2 dB end-of-life margin, 2 dB

implementation margin, 3 dB variation from isoflux)

3 dB additional margin in order not to constrain the existing signal

E –133.3 dBW/m² Maximum pfd level E=C+D F 0 dB Ratio between total power and power in 1 MHz G H –133.3 dBW/m²/MHz Maximum pfd per satellite for Glonass C/A characteristics

The table below shows the calculation based on GPS P code.

A –166 dBW Minimum received power level for GPS P code in L2

M.1088

B –23.7 dBm² Effective area of 0 dBi antenna C –142.3 dBW/m² Minimum pfd level for 1 satellite C=A-B D 10 dB Maximum/minimum pfd ratio (2 dB end-of-life margin, 2 dB

implementation margin, 3 dB variation from isoflux)

3 dB additional margin in order not to constrain the existing signal

E –132.3 dBW/m² Maximum pfd level E=C+D F 9.9 dB Ratio between total power and power in 1 MHz G H –142.2 DBW/m²/MHz Maximum pfd per satellite for GPS P code characteristics

______________

SE 28 : worst case pfd System 1 System 2-

1 System 2-3

System 3-1

System 3-2

System 4 WPR

BiF 0.78 0.69 0.69 6.4 4.4 1.2 2.5 MHz Receiver noise figure NF

2.00 2.00 2.00 4.70 4.70 3.50 1.50 dB

Antenna maximum gain Gr

33.50 31.70 38.90 38.20 38.20 33.50 33.50 dB

N0 oise -142.91 -143.44 -143.44 -131.07 -132.70 -139.54 -138.35 dBW/recei

ver band

I0 -148.91 -149.44 -149.44 -137.07 -138.70 -145.54 -144.35 dBW/receiver band

Antenna polarization

H,V,LHC,RHC

V,C V,C H H V H

Polar discrimination Polar

0.00 0.00 0.00 3.00 3.00 3.00 3.00 DB

Radar receiver insertion loss Lr

2.00 2.00 2.00 2.00 2.00 2.00 2.00 DB

Spectral PFD -156.68 -155.41 -162.61 -146.54 -148.17 -150.31 -149.12 DBW/m2/receiver band

Spectral PFD -155.60 -153.80 -161.00 -154.60 -154.60 -151.10 -153.10 DBW/m2/MHz

Calulated from rec. ITU- R M

1463

Pfd limit : -161 !!!

objectives of a statistical approach

- The worst case scenario uses the gain of the main beam of the radars

- Satellites are not always in the main beamObjective of further works :

to present a statistical view of harmful interferenceto propose a pfd limit acceptable for everybody

Resolution 606 : statistical approach

AssumptionsRadar modelModels of satellites constellations :

GPS GALILEO

Harmful interference criteria to radars : recommendation ITU-R M 1461general consideration

Resolution 606 : statistical approachRadar model

Rec ITU-R M 1463 does not give enough information on radiation pattern of radars

Measured radiation pattern of a civil aviation radar

- Calculated PFD for “ no harmful

interference” : -154 dBW/m2/1MHz

Methodology

Modelisation of a satellite constellationGALILEO

27 satellites – 3 orbital plansAngle of orbital plans 55° right ascension : 0 – 120 – 240°Anomalies : every 40° from 0° – 13.33° – 26.66°Altitude : 23600 km

GPS : 24 satellites, 6 orbital plansAngles of orbital plans :55 ° Right ascension : 0 – k * 60°Anomalies : every 90°Altitude : 20 200 km

Methodology

Calculation of satellite elevation- For one satellite- For all satellites of an orbit- For all satellites of the constellation

(here for a latitude of 47° N)

Maximal gain

Gain for one satellite

Max gain for the whole constellation

-1.5 -1 -0.5 0 0.5 1 1.5

x 105

-10

-5

0

5

10

15

20

25

30

-3 -2 -1 0 1 2 3

x 104

14

16

18

20

22

24

26

28

30

Methodology

Distribution of Gain :

prob (gain<g) = period (gain<g)/total

period

-10 -5 0 5 10 15 20 25 30 350

0.2

0.4

0.6

0.8

1

Methodology : harmful interference criteriaRec. ITU-R M 1461 : threshold I/N = -6 dBFrom simulations :

Elevation, azimuth function of timeSeveral minutes per degree.- Between several antenna rotations, the satellite

azimuth and elevation can be considered as fix elements

- from the operator point of view, when there is jamming in a direction, this direction is jammed all the time and not only the percentage of tim the radar scans in this direction…

- The “harmful interference period” is the total period in which I/N superseded the threshold for at least one direction : results from the vertical radiation pattern

- The horizontal radiation pattern gives the width of the jammed area.

Methodology

Harmful interference I/N = -6dB (rec ITU-R M 1461)

For a given PFD :Prob (interference) = prob

(Gain >PFDwc+Gmax - PFD)

With :PFDwc = PFD worst case =

-154 dBW/m2/1MHz for our radar -180 -170 -160 -150 -140 -130 -120 -110 -100 -90 -80

0

0.2

0.4

0.6

0.8

1

Resolution 606 : statistical approach

First results

For pfd as proposed, probability of harmful interference is above 20 % for one satellite !!!

-180 -160 -140 -120 -100 -80 -60 -400

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Resolution 606 : statistical approach

First results

For pfd as proposed, probability of harmful interference is almost 100 % for the constellation !!!

-180 -170 -160 -150 -140 -130 -120 -110 -100 -90 -800

0.2

0.4

0.6

0.8

1

Resolution 606 : statistical approach

Attempts of explanations :Most of the time, there are

one or more satellite with a low elevation

high gain of radiation pattern

4 periodsOne orbital plan

Three orbital plans

Resolution 606 : statistical approach

But…This approach gives

similar results with GPS today

No interference seen until now…

So, WHY ??? Bad assumptions ?Harmful interference

criterias ?Radar signal

processing…Wrong models ?

Resolution 606 : statistical approach

But…This approach gives

similar results with GPS today

No interference seen until now…

So, WHY ??? Bad assumptions ?Harmful interference

criteria ?Radar signal

processing…Wrong models ? -180 -170 -160 -150 -140 -130 -120 -110 -100 -90 -80

0

0.2

0.4

0.6

0.8

1

GPS

GALILEO

PFD

Prob (harmful interference) for GPS and GALILEO

Resolution 606 : Present problem

WHY are there no interference declared today between GPS and radars in L2 band ?

Wrong assumptions ?, false calculations ? more studies must be made

Not enough data about radars ?Radiation patternsInterference measurement

Interference criteria not adequate ?

Resolution 606 : more information from NATO

US : Same approachCalculations with ITU-R M 1461 and M 1463

recommendations predicts interferences from current GPS, but : no interference to date

Need to examine other methodologiesStudy with 8 US radarsStatistical approach, study of different criterias…

Operational tests : To configure a GPS satellite to transmit C/A signal on L2

(1227 MHz)