Enhancing the Directivity of Phased Array Antennas Using Lens-Arrays

Small phased-array antennas can be combined with dielectric lenses or planar lens-arrays to form directive beam-steering system. The use of the lens increases the size of the radiating aperture and enhances the directivity of the phased array, but it also reduces its scan field of view. However, the effect can be controlled by properly designing the phase delay profile across the lens. This paper presents the formulation and methodology for designing modified lenses that can allow the desired scan angle. The utility and limitations of the proposed approach will be illustrated by considering several design examples. Simulations suggest that a directivity enhancement of > 2 dB and wide scan field of view (up to 45° off boresight) can be obtained for compact radiation systems employing small lenses and short separations between the lens and phased array. Larger directivity improvements in the range of tens of dB's are possible in systems with limited scanning capability by employing large lenses and greater phased array-lens separation. Ease of implementation and the ability of the proposed topology to adapt to the system requirements make this topology an interesting candidate for various millimeter-wave radio applications.