Aircraft Obstruction of Microwave Links

Richard E. Skerjanec; R. W. Hubbard

Abstract: Conversion to digital transmission has renewed the concerns about what effects aircraft obstruction of microwave links have on user quality. This is of particular concern where it is necessary to install a telecommunication system that crosses runways and taxiways where the frequency of obstruction may be great. A limited measurement program at 8 GHz at Atlanta and Chicago Airports was undertaken to determine if a condition existed that could cause excessive error rates on digital systems. Measurements were made of the received signal level together with the impulse response of the transmission medium. Measurement results indicate that during takeoff and landing, aircraft can cause signal level fades to 20 dB. Modern system margin is usually sufficient to cope with such fades. The impulse response measurements at Atlanta did not reveal any delayed or distorted pulses that would indicate excessive multipath and frequency selective fading. However, slight distortion from taxiing aircraft at Chicago was observed. The implication of this detected distortion is reflected in the potential of a distorted asymmetrical frequency response within the 15 – 20 MHz passband of a microwave digital receiver.

Keywords: impulse response; microwave propagation; digital transmission; aircraft obstruction

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