Frequency-controlled broadband and broad-angle beam scanning is proposed using a circular-patch array fed by planar spoof surface plasmon polaritons (SPPs). Here, a row of circularly metallic patches is placed near an ultrathin planar spoof SPP waveguide. When the SPP wave is transmitted through the waveguide, the circular patches are fed at the same time. Because of the phase difference fed to the patches, the proposed structure can realize wide-angle beam scanning from backward direction to forward direction as the frequency changes, breaking the limit of traditional leaky-wave antennas. Both numerical simulations and measured results demonstrate good performance of the proposed structure. It is shown that the scanning angle can reach 55° with an average gain level of 9.8 dBi. The proposed frequency scanning patch array is of great value in planar integrated communication systems.

We present a novel method to design a conventional Fabry-Perot (F-P) antenna but with low scattering. Combining a coding metasurface and an F-P antenna together could effectively reduce the scattering and keep high gain simultaneously. The coding element consists of two layers of square metallic patches printed on both sides of a dielectric substrate. The bottom metallic patch helps form a partially reflecting surface (PRS) for the F-P antenna, while the upper metallic patch is utilized to construct the coding metasurface with an optimized coding sequence, aiming to reduce the scattering of the F-P antenna by redirecting electromagnetic energies in all directions. Based on the specially designed coding metasurface, a good scattering reduction without degrading the radiation performance of the F-P antenna is achieved. Both simulated and experimental results demonstrate the excellent performance of the proposed antenna, with a peak measured gain of 19.8 dBi and a significant scattering reduction in the frequency range of 8-12 GHz.

In this study, an ultra-broadband dielectric-resonator-based absorber for microwave absorption is numerically and experimentally investigated. The designed absorber is made of the carbon-loaded Acrylonitrile Butadiene Styrene (ABS) polymer and fabricated using the 3D printing technology based on fused deposition modeling with a quite low cost. Profiting from the fundamental dielectric resonator (DR) mode, the higher order DR mode and the grating mode of the dielectric resonator, the absorber shows an absorptivity higher than 90% over the whole ultra-broad operating band from 3.9 to 12 GHz. The relative bandwidth can reach over 100% and cover the whole C-band (4–8 GHz) and X-band (8–12 GHz). Utilizing the numerical simulation, we have discussed the working principle of the absorber in detail. What is more, the absorption performance under different incident angles is also simulated, and the results indicate that the absorber exhibits a high absorptivity at a wide angle of incidence. The advantages of low cost, ultra-broad operating band and a wide-angle feature make the absorber promising in the areas of microwave measurement, stealth technology and energy harvesting.

In this study, a cylindrical-water-resonator-based absorber with an ultra-broad operating band at microwave wavelengths is demonstrated theoretically and experimentally. By utilizing the dielectric resonator mode, spoof surface plasmon polariton mode, and grating mode of the cylindrical water resonator, the proposed absorber exhibits an absorptivity higher than 90% over almost the entire ultra-broad operating band from 5.58 to 24.21 GHz, with a relative bandwidth as high as 125%. The angular tolerance and thermal stability of the proposed absorber are simulated, and the results indicate that the absorber performs well in a wide range of angles of incidence and exhibits a weak dependence on the water temperature. The low cost, ultra-broad operating band, good wide-angle characteristics, and thermal stability make the absorber promising for applications in antenna measurement, stealth technology, and energy harvesting.

A filtering magnetoelectronic dipole antenna (MEDA) with quasi-elliptic gain response and wide operating band is investigated. Different from the conventional MEDA, the antenna studied here is fed by fork-shaped microstrip line aperture-coupled excitation. The intrinsic radiation null of the MEDA at the lower passband edge is utilized, and a mathematical model is firstly put forward to demonstrate its working mechanism. Four driven stubs connected to the shorted walls of MEDA are used to excite the planar dipole arms. The parasitic inductor and the coupling capacitor introduced by driven stubs form an equivalent low-pass filter network, leading to a radiation null at higher frequency. Furthermore, a third radiation null is generated by introducing two quarter-wavelength U-shaped shorted stubs to improve the out-of-band suppression. Besides, due to the introduction of multiple coupling structure, including the fork-shaped microstrip line coupling slot and driven stubs, a wide operating band can be realized while maintains a low profile of 0.15 wavelength. Experimental results show that an impedance bandwidth of 53.5% (2.95 to 5.1 GHz) is achieved and an out-of-band suppression level higher than 17.9 dB is obtained. What’s more, an average gain of 8 dBi and good radiation patterns are realized over the whole operating band.

A wideband single-layer substrate integrated waveguide (SIW) filtering slot antenna with compact structure is investigated, which is originated from a SIW resonant cavity operating at its TE ₁₁₀ mode. A straight radiating slot is integrated on the top surface of the cavity. The resonator can be splitted into two half-mode resonators, generating a radiation null at higher edge of the passband. At same time, two U-shaped slots are etched on the bottom surface of the cavity. One of the U-shaped slots is used to introduce a radiation null at the left edge of the passband while the other U-shaped slot introduces the modified half-TE ₁₁₀ mode in the right half cavity, broadening the bandwidth of the antenna. Finally, the third-order filtering antenna is obtained with 11.84% impedance bandwidth in only one SIW resonant cavity. To validate design, a prototype is fabricated and measured. Compared with other designs, the proposed antenna owns features of simple structure, wide bandwidth, and compact size, satisfying the increasing requirement for the miniaturization and integration of RF devices.