The design of programmable metasurface with continuous and independent manipulation of reflective phase and amplitude is proposed and the dynamic control of the bi-static radar cross-section (RCS) is realized correspondingly. The total unit cell is composed of the passive patch antenna for receiving and radiating the electromagnetic (EM) wave, and the active components including the programmable phase shifter and attenuator for dynamic controlling the reflective phase and amplitude continuously and independently. Accordingly, the main direction of bi-static EM scattering can be governed by distributing the reflective phase of each unit cell under the synthesizing method in the far field. Also, the amplitude of bi-static RCS can be operated by changing the reflective amplitude of metasurface. Furthermore, a prototype of programmable metasurface consisting of 121 elements is fabricated. The EM performances of continuous and independent controlling the reflective phase and amplitude are observed, and dynamic control of the bi-static RCS is achieved in our measurement.

An ultrathin tunable absorber for the ultrahigh frequency (UHF) band is presented in this paper. The absorber is a single-layer structure based on the topology of a Salisbury screen, in which the conventional resistive layer is replaced by an active frequency-selective surface (AFSS) loaded with resistors and varactors. The reflectivity response of the absorber can be controlled by adjusting the reverse bias voltage for the varactors, which is verified by both simulated and measured results. The experimental results show that the reflectivity response of the absorber can be modulated below −10 dB over a frequency band ranging from 415 to 822 MHz. The total thickness of the absorber, 10 mm, is equivalent to only λ/72 of the lower limit frequency. The absorbing mechanism for the designed absorber is illustrated by simulating the volume loss density distributions. A detailed analysis is also carried out on the basis of these parameters, such as the AFSS shape, resistor, thickness of the foam, thickness and permittivity of the dielectric substrate, and incident angles, which contribute to the reflectivity of the AFSS absorber.

In this paper, a low-profile, double-layer absorber with ultra-broadband absorption and large-angle stability is proposed. In order to improve the angular stability, the square ring with concave–convex deformation is designed. It can expand the current path to realize the miniaturization of the absorber, which decreases the influence of oblique incident on absorption. The equivalent circuit model provides detailed resonance and admittance analysis, showing the existence of three resonances working together to achieve broadband absorption. The simulated results illustrate that the designed unit can achieve above 80% absorption within 2.09–18.1 GHz. The angular stability is up to 50° under TE/TM polarization with a period of 0.07 λ_L (the wavelength of the lowest operating frequency). The 300 mm × 300 mm prototype absorbers were fabricated for demonstration, with a total thickness of 0.096 λ_L. The measurement results are consistent with the simulated results, which shows that the designed absorber unit can achieve ultra-broadband and large-angle absorption. The performance of devices can be widely applied in infrared detection, radiation refrigeration, and stealth technology.