Glide path signal transmission system

Claim 1

A glide path signal transmission system for indicating to an aircraft a perdetermined glide path within an aircraft guidance region comprising: carrier wave radio frequency generating means for generating a carrier wave; modulating means connected to receive and modulate the carrier wave and to provide at a first output terminal a first modulated signal comprising the carrier wave modulated with a first modulating frequency and to provide at a second output terminal a second modulated signal comprising the carrier wave modulated with a second different modulating frequency; hybrid signal combining means connected to receive said first and second modulated signals and to provide from them two different output signals having a predetermined relationship to one another and in each of which a constant but different relationship exists between said modulating frequencies; first signal drive means connected to receive one of said two different output signals and second signal drive means connected to receive the other of said two different output signals and to develop therefrom a distribution of signal currents; and an antenna arrangement comprising a first antenna array connected to receive signal currents from said first signal means, a second antenna array connected to receive signal currents from said second signal drive means, said antenna arrays having their centres separated in a vertical direction and being individually constituted by antenna elements of which a predetermined number are common to both arrays such that each of said signal drive means supplies the elements of its associated array with a distribution of signal currents in such manner as to substantially obviate reflected radiation of the transmitted radiation within said aircraft guidance region, and said elements unique to the first and second arrays are fed by their respective drive means with first and second drive signals respectively whereas the elements which are common to the two arrays are fed with a combination of signals from said drive means.