Aircraft radio navigation system - uses Fresnel and Fourier correlations performed on sum and difference signals derived from two ground beacons

摘要

The aircraft mounted radio navigation system simultaneously determines an angular positioning factor and the distance of aircraft from two ground beacons. These beacons each having a rectlinear moving source which at each instant in time move oppositely to each other. The beacons are fed by electromagnetic waves of neighbouring radio frequency. The system uses multiplication followed by filtering to produce beat frequencies which are less than the signals received from each of the beacons. These beat frequencies are multiplied together. They are then filtered so as to obtain on one channel the difference of the beat frequencies and on the other channel the sum of these frequencies. A Fourier correlation is performed on the difference channel and a Fresnel correlation is performed on the sum channel.