Optical technique for broadbanding phased arrays

An optical method for broadbanding a phased array is considered. A narrow band feed-through aperture lens comprised of pick-up elements, radiating elements, and
360\deg
type phase shifters is fed by a small feed array with an intervening passive lens. The lens has fixed frequency-sensitive properties. The feed array has variable time delay compensators which are selected in accordance with the desired scan angle in the far field. Using geometrical optics, design formulas are derived that relate bandwidth and scan angle to the minimum number of variable time delayers. To demonstrate performance, diffraction theory is used to calculate patterns, sidelobe levels, and efficiencies as a function of bandwidth and scan angle out to
50\deg
scan for several aperture sizes. In the worst cases, the optical system provides somewhat less gain than the comparable constrained subarray antenna; however, it always provides much better sidelobe levels.