Flat-topped beams from a uniform amplitude rectangular aperture

A useful property of the x*y phase distribution has been discovered which allows a phased array with uniform amplitude taper to have a continuously programmable beamwidth, or zoom mode, based on a single parameter without need for optimization. It has applications for a broad area coverage mode for transmit arrays, or broad acquisition beams for arrays in satellite terminals and missile seekers. It is readily switchable with a pencil beam mode without excessively adding to the complexity of the beamsteering computer. Beam shaping for 2D arrays has generally taken the simple theoretical form of an inverse Fourier transform of the required coverage region. The large amplitude variations which typically result cause reduced radiated power and low overall efficiency when implemented in an active transmit phased array using equal power modules. Therefore it is desirable to find aperture phase functions which form shaped beams while maintaining equal excitation amplitude on the elements.