Proactive Conformal Antenna Array for Near-Field Beam Focusing and Steering Based on Curved Substrate Integrated Waveguide

The quadratic phase distribution on the antenna aperture is necessary to produce a near-field-focused (NFF) beam. The generation, as well as the steering of the quadratic phase distribution, is difficult for a series-fed NFF array antenna, especially for a large-aperture application. This is because the phase control capability of the planar series-fed beam-forming network is limited. In this paper, a curved substrate integrated waveguide (SIW) is employed as the feeding carrier to enhance the amplitude and phase control capability. The spatial placement of the SIW slot array antenna can be sufficiently used to synthesize the desired NFF beam. As examples, two kinds of proactive conformal SIW NFF slot array antennas, working in the standing-wave mode and the leaky-wave mode, have been developed. Both of them have the ability to generate the high-quality NFF beam. In addition, the proactive conformal SIW leaky-wave slot array antenna has the stable focal height over a wide steerable range. After careful analysis and design, these two kinds of antenna arrays are fabricated and proactively conformal to 3-D-printed frameworks with the desired shape. The theoretical analysis and simulated results are verified by experimental results.