Simulated Doppler navigational system with second order diversity

Claim 1

Radio direction finding apparatus for navigational angle determination comprising: a first antenna array having a plurality of separately excitable first elements arranged in a two-dimensional pattern in n positions in the coordinate of measurement of said navigational angle and m coordinate positions orthogonal thereto, said first elements lying in a first array plane and occupying at least a portion of the element positions thereby defined, where q is the product of m and n; a second antenna array having a plurality of separately excitable second elements p, where p> m arranged in a line substantially parallel to a line of said m element positions; first means for energizing said first elements in a program in which the energized element during each successive element dwell time is advanced in said n coordinate position linearly as a function of time, the m position of said element energized at any time being simultaneously controlled as to m position according to a pseudo-random program; second means for successively energizing a contiguous group of said second elements comprising the same number of said second elements as are energized in each scan cycle within said first array, said energization of said second elements being effected according to a program whereby the lateral spacing between the first array element and the second array element remains constant throughout each of said scan cycles; and third means operatively associated with said second means for varying the location of said contiguous group of elements among said p elements of said second array which are energized by said second means for each successive scan cycle, said location remaining constant during each scan cycle.