Ka-Band Near-Field-Focused 2-D Steering Antenna Array With a Focused Rotman Lens

This paper presents a near-field-focused (NFF) substrate-integrated waveguide (SIW) antenna at a center frequency of 35 GHz with 2-D steerable focus. The proposed antenna is achieved by combining an NFF leaky-wave slot antenna array with a focused multibeam SIW Rotman lens. In most of the existing NFF planar antennas, the total phase distribution on the radiating aperture is separated into two parts with respect to the E-plane and the H-plane, which leads to a large error and deteriorates the NFF performance. Here, a modified NFF planar antenna synthesis method is proposed to calculate the desired phase distribution on the aperture and completely eliminate such an error at the center frequency. The linear NFF leaky-wave slot antenna is designed to scan the focal point in the H-plane with the frequency. The 15 leaky-wave slot antennas are grouped in a special topology and excited by the focused SIW Rotman lens. In this case, multiple focal points can be generated in the E-plane. Moreover, an SIW matching load is developed to improve the NFF beam performance. The whole NFF antenna is integrated into a single-layer substrate. The measured results are in agreement with the simulated ones.