Two-Dimensional Near-Field Focusing Folded Reversely Fed Leaky-Wave Antenna Array With High Radiation Efficiency

This paper presents a 2-D near-field focusing (NFF) substrate-integrated-waveguide (SIW) leaky-wave antenna (LWA) array with high radiation efficiency. In most of the existing 2-D NFF antenna arrays, the required quadratic phase and balanced amplitude distribution are achieved by the use of the transverse topology with a complex feeding network or the simple radial topology with high polarization loss. Here, a folded reversely fed LWA with transverse polarization is proposed to achieve natural balanced radiation with a sample series-fed network. Meanwhile, the width of the single linear LWA is complementary with the reversely fed topology. In this case, the SIW with a stepped width is applied to achieve a quasi-uniform slot distribution and to avoid the spurious radiation. Then, all reversely fed linear LWAs are connected by the meander-line structure, which can simplify the feeding network and enhance the radiation efficiency. The limitation of the NFF LWA in radiation efficiency is broken. The 2-D focusing principle and the design process of the proposed antenna are presented in this paper. As an example, a 2-D focusing SIW LWA array operated at 35 GHz with an 80% radiation efficiency is fabricated and measured.