Diverse electromagnetic (EM) responses of a programmable metasurface with a relatively large scale have been investigated, where multiple functionalities are obtained on the same surface. The unit cell in the metasurface is integrated with one PIN diode, and thus a binary coded phase is realized for a single polarization. Exploiting this anisotropic characteristic, reconfigurable polarization conversion is presented first. Then the dynamic scattering performance for two kinds of sources, i.e. a plane wave and a point source, is carefully elaborated. To tailor the scattering properties, genetic algorithm, normally based on binary coding, is coupled with the scattering pattern analysis to optimize the coding matrix. Besides, inverse fast Fourier transform (IFFT) technique is also introduced to expedite the optimization process of a large metasurface. Since the coding control of each unit cell allows a local and direct modulation of EM wave, various EM phenomena including anomalous reflection, diffusion, beam steering and beam forming are successfully demonstrated by both simulations and experiments. It is worthwhile to point out that a real-time switch among these functionalities is also achieved by using a field-programmable gate array (FPGA). All the results suggest that the proposed programmable metasurface has great potentials for future applications.

An electronically reconfigurable reflectarray antenna (RRA) with 10 × 10 elements is presented with a detailed design procedure for an improved beam-scanning performance. The element, designed at Ku band using a simple patch structure with one PIN diode and two substrate layers, can be electronically controlled to generate two states with 180° phase difference and low reflection loss. A reflectarray prototype is fabricated and experimentally studied for proof of principle. The limitations of the small aperture size are analyzed in detail, and synthetic optimizations of both feed location and aperture phase distribution are used to improve the beam-scanning performance of the prototype. Experimental results agree well with the full-wave simulations, and scan beams within ±50° range are obtained with a maximum aperture efficiency of 17.9% at 12.5 GHz. Consistent scan beams are obtained from 11.75 to 13.25 GHz. Furthermore, the versatile beam-forming capability of the RRA is also demonstrated by a wide-beam pattern synthesis. A fast beam-switching time (12 μs) is theoretically analyzed and verified by the measurement.

A dual-frequency reconfigurable reflectarray (RRA) is proposed and verified experimentally. The RRA consists of 1600 electronically controllable elements. By integrating only a single PIN diode, the proposed element is capable to operate at two working frequencies with 1-bit phase resolution. The dual-frequency mechanism is explained through the mode analysis, and a parametric study is performed to provide guidelines for determining the two working frequencies. As an example, a 1600-element RRA prototype is realized by assembling five identical 8 x 40 subarrays. An field programmable gate array control board is used to achieve real-time phase control of each element individually. The experimental results show that the broadside gains of the RRA are 29.3 and 30.8 dBi at 11.1 and 14.3 GHz, respectively. Excellent beam scanning performance is also obtained at both frequencies.

The simultaneous improvement in radiation and scattering performance of an antenna is normally considered as contradictory. In this paper, wideband gain enhancement and radar cross-section (RCS) reduction of Fabry-Perot (FP) resonator antenna are both achieved by using chessboard arranged metamaterial superstrate (CAMS). The CAMS is formed by two kinds of frequency selective surfaces (FSSs). The upper surface of CAMS is designed to reduce RCS based on phase cancellation principle, and the bottom surface is used to enhance antenna gain on the basis of FP resonator cavity theory. Both simulated and measured results indicate that, compared with primary antenna, the gain of the proposed FP resonator antenna is enhanced by 4.9 dB at 10.8 GHz and the 3-dB gain bandwidth is from 9.4 to 11.1 GHz (16.58%). Meanwhile, the RCS of the proposed FP resonator antenna is reduced from 8.0 to 18.0 GHz, with peak reduction of 39.4 dB. The 10-dB RCS reduction is obtained almost from 9.6 to 16.9 GHz (55.09%) for arbitrary polarizations. Moreover, the in-band RCS is greatly reduced, owing to the combined effect of CAMS and FP resonator cavity.

In this letter, a wide-beam (at two main planes) antenna is proposed. To broaden the 3-dB beam-width of the original antenna, a pair of parasitic patches with metallic vias is creatively arranged on either side of the original radiation patches. Based on the proposed antenna element, two linear phased arrays are fabricated and measured. Measured results reveal that the wide-angle scanning capability of both H-plane and E-plane arrays can be obtained. The scanning beam of the former can cover territories ranging from -90 to 90, with gain loss within 3dB (8GHz-11GHz). The scanning beam of the latter can cover territories ranging from -70 to 70, with gain loss of 3-5dB (8GHz-10GHz).

A novel integration strategy of microstrip antenna and metasurface is proposed to achieve low-radar cross section (RCS) and improved radiation performance simultaneously. Aimed at the applications in stealth cylindrical carrier, the antenna has a circular configuration, and the metasurface cells are closely arranged around the radiation patch in a concentric ring-type manner. Moreover, the mode analysis method is fully used to analyze the antenna's working mechanism and guide the optimization process. Owing to the addition of metallic vias, the original quasi-TM ₃₀ mode is altered to three series-TM ₁₀ modes and thus enhanced gain is achieved. Interestingly, the addition of vias also generates a new resonance which widen the antenna's impedance bandwidth. In another aspect, both in-band and out-of-band RCS reductions are obtained simultaneously. Finally, two prototypes are fabricated to validate the proposed design strategy. Good agreements between measurements and simulations are obtained. Measured results show that the gain of the proposed antenna is at least 3 dB higher than the conventional antenna in the entire operating band, and obvious RCS reduction is achieved from 4.0 to 8.5 GHz concurrently.