A broadband localizer antenna array with an even number of elements is supplied by a backmatched power dividing network comprising two chains of directional couplers and a group of hybrids which divide the power among the elements in accordance with geometrical progessions. The center elements in the array may be spaced 0.6 wavelength apart at the average frequency. Other spacings between the elements are greater than 0.6 wavelength.

A two-frequency capture-effect instrument landing system employs a single localizer antenna array for both course-frequency and clearance-frequency radiation. The composite course and clearance signals are formed by networks that utilize trees of hybrid power dividers to effect unequal power division and distribute the signals to the antenna feeders. Integral monitoring is provided by similar networks, operating backwards in a functional sense, which recombine samples of the RF energy on the antenna elements and separate the same into the basic, frequency-separated course and clearance signal components. Redundant monitoring for antenna fault detection is provided by detecting RF signal levels on unused ports of the monitor circuit power dividers.

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.

Disclosed is an improvement to Integral Monitoring of two-frequency Instrument Landing System Localizer transmitting antenna arrays, by means of which the Clearance signal can be precisely separated from the combined Course and Clearance output of an Integral Monitor recombiner and monitored as if it existed alone. A first detector detects a composite Clearance and Course signal input, and sends an output to a separation filter which does not pass frequencies of 0, 90 or 150 hertz, but does pass frequencies of the difference between Course and Clearance frequencies (.DELTA.f), .DELTA.f.+-.90 hertz, and .DELTA.f.+-.150 hertz. The output of the filter is input to a second detector which measures the difference between the percentages of 90 and 150 hertz amplitude modulations of an amplitude modulated carrier having a frequency .DELTA.f.