30-01-2012 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 Radar characteristics Criterion DA2GC transmission characteristics DA2GC Aircraft Station influence on radar DA2GC Ground Station influence on the radar Conclusions

Radar characteristics Vertical/Left-hand circular Recommendation ITU-R M.1638 [1] , in particular Radar N and Radar O Characteristics Radar N Radar O Function Instrumentation Platform type Ground Tuning range (MHz) 5 400-5 900 Modulation Pulse/chirp pulse Chirp pulse TX power into antenna 1.0 MW 165 kW Pulse width (µs) 0.25-1 (plain) 3.1-50 (chirp) 100 Pulse rise/fall time (µs) 0.02-0.1 0.5 Pulse repetition rate (pps) 20-1 280 320 Chirp bandwidth (MHz) 4.0 8.33 RF emission bandwidth (MHz) at: -3 dB -20 dB 0.9-3.6 6.4-18 9.9 Antenna pattern type Pencil Antenna type Phased Array Antenna polarization Vertical/Left-hand circular Antenna main beam gain (dBi) 45.9 42 Antenna elevation beamwidth (degrees) 1.0 Antenna azimuth beamwidth (degrees) Antenna rejection (1st SLs and remote SLs) (dB) -22 Antenna height (m) 20 Receiver IF 3 dB bandwidth (MHz) 2-8 8 Receiver noise figure (dB) 11 5 Minimum discernible signal (dBm) -107, -117 -100

Criterion ITU recommendation: interference level 6 dB below the receiver noise power level Pn = F k Ts B [W]   F : receiver noise figure k : Boltzmann’s constant (1.38×10-23 [J/K]) Ts : system noise temperature [K] B : instantaneous bandwidth [Hz].

DA2GC transmission characteristics Aircraft Station Ground Station Maximum transmit power (dBm) 28 25 Maximum antenna gain (dBi) 17 23 Max EIRP (dBm) 45 Antenna height (m) 3000 – 13000 30 Automatic transmit power control (dB) Channel bandwidth (MHz) 20 (TDD) 10 (FDD)

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

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.

Conclusions Unwanted emissions in radar instantaneous band has been considered. Blocking should also be considered (out-of-radar-band) An additional suppression of the OOB DA2GC emissions of 19 – 24 dB is required Interference potential within10 km around every DA2GC Ground Station Is there a spectral mask for the DA2GC Aircraft Station? Interference potential is significant