A microwave beacon and guiding signals for airports and their approaches

A novel circular array of 90 equally spaced vertical dipoles is described. It is driven by just one element. When the spacing, length, and radius of the identical elements are properly chosen, the entire array is resonant with large currents in each element. These alternate 180/spl deg/ in phase and set up a far field that consists of 90 sharp spikes separated by 90 nulls. When dimensioned for a microwave frequency of 3 GHz, the array generates a field pattern that can be applied to provide a microwave beacon and guiding signals for aircraft approaching an airport. These would supplement the normal central high-intensity light and the approach lights, and provide a potentially useful guidance system for coastal airports embedded in dense fog that obscures the lights.