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
Radar characteristics
Criterion
DA2GC transmission characteristics
DA2GC Aircraft Station influence on radar
DA2GC Ground Station influence on the radar
Conclusions

2. 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)
Modulation
Pulse/chirp pulse
Chirp pulse
TX power into antenna
1.0 MW
165 kW
Pulse width (µs)
(plain) (chirp)
100
Pulse rise/fall time (µs)
0.5
Pulse repetition rate (pps)
320
Chirp bandwidth (MHz)
4.0
8.33
RF emission bandwidth (MHz) at: -3 dB
-20 dB
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

3. 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].

4. 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)

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

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.

7. 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