A frequency and polarization reconfigurable antenna which is composed of a metasurface, a planar slot antenna and a metallic reflector is proposed in this paper. The metasurface is made up of 64 identical patches, and all the patches are on the top surface of the substrate. In order to extend the bandwidth of the antenna, the planar slot antenna adopts a double slot structure. The reconfiguration of frequency and polarization can be achieved by adjusting the relative positions between the metasurface and the planar slot antenna. The antenna can be reconfigured to linear polarization, left-hand and right-hand circular polarizations. At the same time, the gain of the antenna is improved. In order to verify this method, a frequency and polarization reconfigurable antenna is designed. Simulation and experimental results show that the polarization reconfiguration can be achieved from 8GHz to 11.2GHz (fractional bandwidth of 33.33%), and the maximum gain achieves 16.5dBi.

In this letter, a 2×2 low profile broadband triple-mode orbital angular momentum (OAM) array antenna is presented, which can be dynamically controlled with electrostatic method. The antenna element consists of a 4×4 metasurface array, a 90° phase-shifting reconfigurable feed network (RFN), and a square driven patch with two switchable feeding ports (SWP). With the computer-assisted micro-controller unit (MCU), the PIN diodes direct current (DC) bias voltage on the RFN and SWP, the OAM modes can then be dynamically switched between l = +1, l = -1, and l = 0. The OAM beams of mode l = ±1 and mode l = 0 have been generated in the broad frequency with the impedance band of 4.9 GHz to 6.5 GHz and 5.0 GHz to 6.3 GHz, respectively. The experimentally measured peak gains of the triple-mode are 11.17 dBi, 11.05 dBi, and 15.19 dBi, respectively. Both the simulation and experiment demonstrate that the proposed antenna exhibits several advantages such as mode reconfigurable ability, broad frequency band, high directivity, and good helical phase front of the OAM waves.

In this letter, a 2x2 wideband bidirectional dual circularly polarized (CP) orbital angular momentum (OAM) antenna array at millimeter-wave frequency is presented, which can be used to generate dual-mode simultaneously by the sequential rotation feeding (SRF) method. The proposed antenna array is composed of four bidirectional radiating dual-CP elements that rotate 90 degrees sequentially to each other in the clockwise direction. The antenna element structure consists of two metasurface patch layers which are loaded on the bidirectional cavity-back slot antenna based on substrate integrated waveguide (SIW) technology. Results indicate that the left-hand circular polarization (LHCP) with a mode lOAM = -1 in +z direction and right-hand circular polarization (RHCP) with a mode lOAM = +1 in z direction, over a wide impedance (S11 10 dB) and 3-dB axial ratio (AR) relative bandwidth of 32.3% from 26 to 36 GHz. An acceptable agreement has been achieved with the comparison between the measurement and simulation results. The proposed antenna provides a method of generating multi-mode OAM beams for wideband millimeter-wave wireless communication applications.

In this communication, a new multiple-traces Poggio-Miller-Chang-Harrington-Wu-Tsai (MT-PMCHWT) equation is proposed to simulate the electromagnetic scattering from microstrip structures. Based on the surface equivalent principle, the original object can be decomposed into two independent domains, i.e., the exterior region (free space) and interior region (microstrip). Different from the traditional EFIE-PMCHWT method, in this new multiple-traces method, dielectric surface is discretized with two pairs of meshes, and Robin transmission conditions (TCs) are enforced on the interface between the exterior and interior regions to ensure the continuity of fields. In comparison with the traditional EFIE-PMCHWT, this new MT-PMCHWT has a better iteration convergence property. Additionally, a new multiple-traces electric field/combined field integral equation with better iteration convergence is also proposed. Because the continuity of fields is ensured by TCs, the exterior and interior regions can be discretized with nonconformal meshes, which improves the flexibility and efficiency of the proposed methods substantially.

Rapid and accurate calculation of electromagnetic scattering problems over a wide incident angle range is a difficult but valuable subject in computational electromagnetics (CEM). Traditional methods need to calculate repeatedly at each finer angle step, which lead to low efficiency. Based on the recently proposed compressed sensing (CS) method in CEM, a new scheme is proposed to further improve the computation efficiency, in which CS is used two times to form an undetermined equation model and incident sources including much information of incident angles simultaneously. Theoretical frame and specific formulas are derived in detail, and numerical results verified that it provided an efficient technical route for solving electromagnetic scattering problems.