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A novel Passive Reconfigurable Intelligent Surface (PRIS) with 100 � 100 elements, which is shaped to scatter flattened patterns in broadband, is presented to enhance the signal coverage of the indoor Non-Line-of-Sight (NLOS) area for 5G millimeter wave (mmWave) wireless communications. The signal from the base station antenna as a primary source can be deflected to the NLOS area by the proposed PRIS with a flattened scattering pattern that is insusceptible to being blocked. The broadband meta-atom, realized by the framed four arrow branches, operates from 24 GHz to 30 GHz. The genetic algorithm is applied to optimize the phase shift distribution of PRIS for a shaped pattern. Combining full-wave simulation and 3D ray-tracing simulation, the signal coverage is computed in an indoor L-shaped corridor scenario for 5G mmWave wireless communications. To verify the design, the proposed PRIS is further manufactured and tested. The experimental results reveal that the signal enhancement in the NLOS area by the proposed PRIS with the flattened scattering pattern is superior to the conventional design.

An adaptively smart wireless power transfer (WPT) system is proposed by using a 2-bit programmable metasurface (PMS), in which an in-door dynamic charging application scenario is described and near-field focused (NFF) technique is adopted to transmit wireless powers. Theoretical analyses of NFF PMS are presented to illustrate its WPT capabilities. To implement dynamic WPTs, digital phase-shift quantization of PMS element is investigated, indicating that 2-bit quantization scheme is a preferred solution. A 2-bit 1212 PMS operating at 5.8GHz is designed, fabricated and tested. High-power focal spots that can be regulated to focus at different near-field positions are measured in an anechoic chamber. We conduct multiple WPT experiments by using the 2-bit PMS as the transmitter and a 44 microstrip array antenna as the receiver. Experimental results show that the proposed 2-bit PMS can continuously transmit the wireless powers to the receiver even though the target is moving, and the WPT efficiency is maintained over 9.1%, which has about 16.3 dB improvement at the end of the trajectory compared to the fixed NFF beam. This work is one of attempts to thoroughly examine the possibility of the dynamic WPTs using PMS, offering a brand-new manner for the adaptively smart WPT systems.

In this letter, we present a holographic metasurface (HMS) based on an orthogonally discrete unit-cell. The proposed unit-cell possesses discrete surface impedance tuning abilities in two orthogonal directions, providing flexible beam formation as a scalar unit-cell and polarization control as a tensor unit-cell. Operation principle and design formulas for generating independently linearly polarized beams and circularly polarized beams using the orthogonal components are concluded. Two example antennas utilizing this HMS are measured to demonstrate the beam formation and polarization control abilities at 11.0 GHz. The first example antenna generates dual beams with independently linear polarizations whereas the second example antenna generates dual beams with independently circular polarizations. Our letter indicates that there exists a middle type of HMS between scalar and tensor HMSs.

This paper presents a dual-polarized reconfigurable antenna loading electronically steerable parasitic patches. The proposed dual-polarized antenna is surrounded by four parasitic patches each of which is mounted by two varactor diodes on the ground. By tuning the varactors, continuous two-dimensional beam-steering can be achieved for each of the polarization. A prototype of the proposed antenna is fabricated and measured. Excellent agreement between the simulated and measured results is observed. It is observed that the maximum beam-scanning angles in E-plane and H-plane are greater than ±25∘, which is suitable for 5G base station applications.

Based on a space–time-coding (STC) transmissive metasurface (TMS), we present the utilization of electromagnetic harmonic spectra in phaseless near-field microwave computational imaging (CI). Each element of the TMS integrates one PIN diode as a switch to independently regulate the transmission amplitude, giving rise to a 14-dB modulation depth at 21 GHz. Using the TMS and two standard horn antennas, a phaseless near-field microwave CI system is established in a single-pixel manner. A simple and effective space–time-coding scheme is detailed to covert a monochromatic signal into multiple harmonics that can be applied to sample the objects. To obtain the sensing matrix built by the harmonics, we propose a method that is developed from the Fresnel diffraction theory. Moreover, we experimentally validate our CI system by reconstructing two metallic objects. The reported STC scheme and the corresponding CI system using TMS could inspire future studies on low-cost imaging hardware development and harmonic wave utilization for high-resolution CI systems.

This paper presents the design of 1-bit programmable holographic metasurface (PHMS) concept for monopulse radar applications. A 1-bit programmable unit-cell with only one PIN diode, which can tune the surface impedance for high impedance or low impedance mode as the PIN diode flipped, is proposed. Holographic patterning technique is employed to realize the sum ( $\Sigma$ ) and difference ( $\Delta$ ) patterns based on the proposed PHMS. A 20×20 ( $5\lambda_{0}\times 5\lambda_{0}$ , where $\lambda_{0}$ is the wavelength at 10.0 GHz) PHMS is built and analyzed using a commercial full-wave simulator. The simulated results suggest that two-dimensional $\Sigma$ pattern scanning and one-dimensional $\Delta$ pattern scanning within ±40° are achieved, which can be applied for tracking radar enabled by monopulse technique.

With the rapid increase of the installed capacity and generation capacity of renewable generation, the topology and structure of modern power systems get more complicated, which promotes higher requirements for power system secure and stable operation. However, power system large-scale blackouts often occur. This paper firstly reviewed 51 major blackouts in history worldwide. The main causes of blackouts were summarized afterwards. Finally, distributed accommodation for distributed energy in energy internet was proposed as a key research direction to avoid large-scale blackouts.