Abstract: It describes a Microwave Landing System wherein.The means for surveillance of the transmissions from the various MLS stations are centralized in a single central station which then commands the various MLS stations. The connection between the central station and the MLS stations is assured by a network of optical fibers.

Abstract: Disclosed is a demodulator for a phase-modulated wave, of the DPSK type for example, applicable to an MLS system. It has a local oscillator, the phase of which is modulated. The signal thus modulated is mixed with the incident signal to be demodulated. The signal coming from the mixer is applied to a loop, the output signal of which:controls the phase modulator;constitutes the output signal of the device.

Abstract: A method and device for monitoring a station in a landing aid system of the MLS type comprising two transmission assemblies. Transmission from the electronic sweep antenna is provided alternately by said two transmission assemblies, the operation thereof being permanently tested and switching thereof being performed as a consequence.

Abstract: A device for monitoring a Doppler VOR system emitting sinusoidal signals at a frequency of 30 Hz, one called "reference" and the other called "variable" whose phase varies with respect to that of the first signal, comprises at least one sensor close to the Doppler VOR system, a first processing device supplying the information emitted by the VOR system in the direction of the sensor and a second device for processing the signal received by the central antenna, said devices comprising means for separating the two upper and lower side-bands of the VHF carrier wave.

Abstract: The device for supplying a Doppler VOR system comprises means for generating the sidebands of an amplitude modulation of a VHF carrier wave, the signals representing the sidebands being amplitude-modulated by a periodic voltage. The device essentially comprises means for coupling and means for adding the amplitude-modulated sidebands so as to produce a signal for supplying antennas having a predetermined spectrum and to compensate for the couplings which exist between the antennas.

Abstract: To maintain a cophasal relationship between two concurrently transmitted waves of the same high frequency derived from a common pilot oscillator, one of these waves being modulated by a low-frequency signal, a phase shifter in cascade with the modulator is controlled by a phase discriminator including a comparator with inputs receiving the two high-frequency waves. An analog multiplier driven by the low-frequency modulating signal converts an error signal from the phase comparator into a unipolar pulsating voltage which, upon integration, yields a control voltage adjusting the phase shifter to correct any relative phase displacement.