System for enabling coherent signal processing at a remote receiving station

In a microwave landing system of the scanning beam type in which a remote receiving station derives angular navigational information from the transmissions of a ground beacon by processing signals received from said beacon, the combination comprising:

• a scanning antenna within said ground beacon, all the radiating elements of which are contemporaneously excited for sweeping a collimated beam through a predetermined angular sector of space;
• first means for generating a first radio frequency signal to energize said scanning antenna;
• second means responsive to said first radio frequency signal for generating a second radio frequency signal therefrom, said second means being responsive to said first radio frequency signal for generating said second radio frequency with a predetermined phase relationship with said first radio frequency signal but offset therefrom in frequency, said second radio frequency signal being substantially continuous during transmission of said first radio frequency signal, and substantially independent of the transmissions and angular position of said scanning antenna;
• and a nonscanning second antenna arranged to provide radiation coverage at least over said sector swept by said scanning antenna, said second antenna being energized by said second radio frequency signal, said second radio frequency signal thereby providing a reference signal at said remote receiving station for coherent processing of said first radio frequency signal received at said remote station.