Abstract: The invention deals with a surveillance system for terrestrial navigational and landing systems, in which the navigational signals being transmitted for aeroplanes or other airborne objects by the navigational and airport landing systems are received and evaluated by a ground-based receiving and control facility. In this system: the receiving and control facility is equipped with a plurality of additional receiving stations; these additional receiving stations operate in the frequency range of the navigational signals; the additional receiving stations are arranged geographically distributed within the transmitting range of the navigational or airport landing system; the signals recorded by the additional receiving stations are forwarded to a central evaluating unit.

Abstract: A method for monitoring a localizer course facility in an instrument landing system, including modulating a course signal at a first signal frequency and at a second signal frequency, and transmitting the modulated course and clearance signals. The method also includes detecting by sensors the modulated course and clearance signals, demodulating the modulated course and clearance signals, monitoring variables obtained from the demodulated course and clearance signals to ensure that the variables are within limit values, and subjecting the demodulated course and clearance signals to Fourier transformation. Also included is determining a first phase difference for a first modulation frequency between the course and clearance signals detected by the sensors and a second phase difference for a second modulation frequency in the course and clearance signals, betweem the course and clearance signals detected by the sensors.

Abstract: The invention relates to an antenna installation with an omni-directional antenna (M) and with an auxiliary antenna (A1) the reception signals from which can be combined in respect of amplitude and phase in such a way that a reception miniumu is produced in a desired orientation in space.

Abstract: A glide path transmitter for an instrument landing system. The transmitter includes several antenna radiators by way of which high frequency signals containing various low frequency modulated carrier and side band components are radiated. The components overlap each other in the far field where they form a guide signal which can be evaluated by aircraft. Phases of the carrier oscillations of the radiated high frequency signals form the guide signal having a set relationship with each other. A separate digitally controlled modulator is provided for each high frequency signal fed to an antenna radiator. The modulator modulates the phase and amplitude of a high frequency oscillation fed thereto according to a given model and inputs the modulated high frequency signal into the antenna radiator allocated thereto, thus reducing the supply network expenditure.