Space modulation

Space modulation is a radio modulation technique employed in an Instrument Landing System (ILS) that uses multiple antennas to transmit signals with varying power levels and phase shifts. These signals combine in the airspace to create a pattern of varying modulation depths that correspond to different positions within the three-dimensional coverage area. This method differs from internal modulation techniques in traditional radio transmitters, where modulation occurs within the transmitter itself. In space modulation, the phase shifts and power variations of the signals interact in the airspace, allowing for precise positional determination by the aircraft’s receiver.

Aircraft equipped with an ILS receiver within the coverage area of the system (including both the localizer and glideslope ranges) can detect varying degrees of modulation based on its position within the three-dimensional airspace. As the aircraft moves through this space, the receiver continuously monitors the phase shifts and power variations of the signals, providing real-time guidance for the approach.

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