A Low-Profile Programmable 2-bit Array Based on a Novel Highly Integrated Element

In this communication, a programmable 2-bit array antenna based on a highly integrated element with low profile and high efficiency is proposed. Based on a ring structure and four PIN diodes, 90° and 180° phase differences can be achieved by changing the resonant dimension and mirroring the states, respectively. The 2-bit element is then obtained by the two methods, and the bias control network for PIN diodes is integrated into the polarization grids. Compared to traditional cascaded phase shifter schemes, the proposed design adopts a new integrated method to simplify the structure, which not only reduces element losses but also simplifies the design of the control section. To further avoid the deterioration of array radiation performance caused by the planar feeding network, its phase and amplitude distributions are optimized by referring to those of the spatial feed in this design. Finally, a low-profile programmable 2-bit array antenna with $8\times 8$ elements is designed and fabricated. The measured results indicate that the designed array can reach a peak aperture efficiency of 67% and achieve a 2-D beam scanning range.