1. A study on the coexistence between Direct Air to Ground Communication (DA2GC) and Radars in the 5 GHz band Peter Trommelen, Rob van Heijster, Arne Theil 1.Dutch C-band radars 2.Radar characteristics 3.Criterion 4.DA2GC transmission characteristics 5.DA2GC Aircraft Station influence on radar 6.DA2GC Ground Station influence on the radar 7.Conclusions 30-01-2012 0

2. 1. Dutch C-band radars 9-10-2012 1 EADS – TRML-3D/32 Raytheon – PATRIOT Weather radars

3. 2. Radar characteristics Specific radar features are not used in the study, rather parameters from ITU-R M.1638 [1], in particular Radar N and Radar O CharacteristicsRadar NRadar O FunctionInstrumentation Platform typeGround Tuning range (MHz)5 400-5 900 ModulationPulse/chirp pulseChirp pulse TX power into antenna1.0 MW165 kW Pulse width (µs)0.25-1 (plain) 3.1-50 (chirp) 100 Pulse rise/fall time (µs)0.02-0.10.5 Pulse repetition rate (pps)20-1 280320 Chirp bandwidth (MHz)4.08.33 RF emission bandwidth (MHz) at: -3 dB -20 dB 0.9-3.6 6.4-18 8.33 9.9 Antenna pattern typePencil Antenna typePhased Array Antenna polarizationVertical/Left-hand circular Antenna main beam gain (dBi)45.942 Antenna elevation beamwidth (degrees)1.0 Antenna azimuth beamwidth (degrees)1.0 Antenna rejection (1st SLs and remote SLs) (dB) -22 Antenna height (m)20 Receiver IF 3 dB bandwidth (MHz)2-88 Receiver noise figure (dB)115 Minimum discernible signal (dBm)-107, -117-100

4. P n = F k T s B [W] F : receiver noise figure k : Boltzmann’s constant (1.38×10 -23 [J/K]) T s : system noise temperature [K] B : instantaneous bandwidth [Hz]. 3. Criterion ITU recommendation on allowed I/N ratio was followed: Interference level 6 dB below the receiver noise power level Radar agility band DA2GC Radar in-band has been investigated (DA2GC out-of-band)

5. Characteristics Aircraft StationGround Station Maximum transmit power (dBm) 2825 Maximum antenna gain (dBi) 1723 Max EIRP (dBm) 45 Antenna height (m) 3000 – 1300030 Automatic transmit power control (dB) 30 Channel bandwidth (MHz) 20 (TDD) 10 (FDD) 20 (TDD) 10 (FDD) 4. DA2GC transmission characteristics

6. 5. DA2GC Aircraft Station influence on the radar An additional suppression of 24 dB is required to avoid interference of the radar to occur due to DA2GC Aircraft Station out-of-band transmissions (-40 dB is not good enough) Several worst case assumptions have been followed.

7. 6. DA2GC Ground Station influence on the radar The separation distance has been determined, assuming Propagation loss, using the ITM Ground Station Antenna Elevation Pattern A distance separation of at least 9.5 km should be taken into account.

8. 7. Conclusions 1.Unwanted emissions in radar instantaneous band has been considered. 2.Blocking should also be considered (out-of-radar-band), as known from experience with 2.65 GHz UMTS-LTE and ATC-radar (2.7 – 2.9 GHz). An additional band-pass filter appears to be effective. 3.An additional suppression of the OOB DA2GC emissions of 19 – 24 dB is required. 4.Interference potential within10 km around every DA2GC Ground Station. 5.Is there a spectral mask for the DA2GC Aircraft Station? 6.Interference potential is significant.