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Abstract

A technique for self-calibration and phasing of a lens-feed array antenna, while normal operation is stopped, utilizes reflected energy of a continuous and coherent wave broadcast by a transmitter (11) through a central feed (10) while a phase controller (21) advances the phase angles of reciprocal phase shifters (14) in radiation electronics (RE1-REN) of the array elements (1-N) at different rates to provide a distinct frequency modulation of electromagnetic wave energy returned by reflection in one mode (switch 19 closed) and leakage in another mode (switch 19 open) from the radiation electronics of each array element. The composite return signal received by a synchronous receiver (12) goes through a Fourier transform processing system (20) and produces a response function for each antenna element. Compensation of the phase angles for the antenna elements required to conform the antenna response to a precomputed array pattern is derived from the reciprocal square root of the response functions for the antenna elements which, for a rectangular array of N.times.M elements, is a response function T(n,m). A third mode of calibration uses an external pilot tone from a separate antenna element (44). Respective responses T.sub.1 (n,m), T.sub.2 (n,m) and T.sub.3 (n,m) are thus obtained from the three modes of calibration. From those, the separate responses T.sub..phi., T.sub.t and T.sub.r of the reciprocal phase shifter, radiation electronics, and synchronous receiver can be obtained by solving the following three simultaneous equations: T.sub..phi. (n,m)=T.sub.1 (n,m) T.sub..phi. (n,m).times.T.sub.t (n,m).times.T.sub.r (n,m)=T.sub.2 (n,m) T.sub..phi..sup.1/2 (n,m).times.T.sub.r (n,m)=T.sub.3 (n,m).

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