Yufan Cao

In this letter, an ultrathin polarization-converting transmissive Huygens element is proposed achieving nearly 100% transmission efficiency for circularly polarized (CP) incident waves. The element consists of a single-layer dielectric substrate with a thickness of only 0.03λ0 and asymmetric S-shaped patches located on both sides. By utilizing surface currents flowing in the reverse direction of the upper and lower patches to form a magnetic dipole, while generating an electric dipole in the orthogonal direction, the electromagnetic response satisfies the Huygens resonance requirement, which makes the transmitarray extremely high efficient for transmission. The independent regulation of CP beam and 360° phase coverage can be flexibly achieved by adjusting rotation angle of the element. The designed element is experimentally integrated to form a metalens antenna to generate directional beam with high gain and low sidelobes. The measured results show that the achieved peak gain of 24.4 dBi at 9.8 GHz with the peak aperture efficiency of 51.3%, which well demonstrated the advantages of low profile, high efficiency, and easy integration of the designed transmitarray structure. Above all, the proposed metalens antenna exhibits superiority for further being applied in device-to-device satellite communications.

A novel method is proposed to achieve radiation performance improvement for patch antennas by using characteristic mode analysis (CMA). In our previous work, a microstrip patch antenna composed of a driven patch and parasitic square patches was presented to realize wideband performance. To improve the radiation performance, the parasitic patches are replaced with split ring resonators (SRRs). Compared with the previous antenna, the unwanted higher‐order modes of the proposed antenna are effectively suppressed based on the simulated results of CMA, leading to good radiation performance. Meanwhile, wideband performance is maintained as well. Simulated results indicate that these two antennas share similar wide bandwidth more than 30%. However, the gains at the higher resonant frequency for these two antennas are 10.8 and 11.75 dBi, respectively. Finally, measured results show that the bandwidth of SRR loaded antenna is from 10.5 to 15.3 GHz, and the gain varies from 8 to 11.5 dBi across the operating bandwidth.

In this paper, a wideband planar substrate integrated waveguide (SIW) horn antenna based on surface wave excitation through loading metamaterials is designed. Strong coupling effect is realized between the employed bilayer metamaterial unit with the top layer as a π‐shaped‐slotted patch while the bottom layer as the complementary cross‐shaped‐slotted patch. The equivalent permittivity of the extended substrate in front of the planar horn aperture can be effectively reduced to unity and impedance mismatching for conventional planar SIW horn antenna can be reduced in a wide bandwidth. Results indicate that the working frequency of the antenna is 12.3–15.8 GHz with the relative impedance bandwidth of 24.6%.

A stacked structure element consists of an arc phoenix patch and an I‐shaped slot is proposed for designing dual‐band reflectarray antenna. The arc phoenix element operates at Ku band, which above the I‐shaped slot element operating at X band. The advantages of this configuration are that the smaller size phoenix element has less shielding of the reradiation energy, and the property of the bottom substrate has no effect on up‐layer due to the I‐shaped element severs as ground plane. Furthermore, two orthogonal polarizations are produced by the radiation characteristics of the slot and the metal strip to eliminate coupling. Based on the element, a reflectarray antenna with a dimension of 140 mm generating two focused beams at orthogonal plane has been simulated, fabricated, and measured. The simulated and measured results are in good agreement in X and Ku bands.

This letter presents a novel broadband substrate integrated waveguide aperture antenna with simple structure and beam steering performance. By using the left‐hand and band gap characteristics of the mushroom‐shaped metamaterials, the main beam of the substrate‐integrated waveguide aperture antenna can be easily switched between the back‐fire and boresight directions. Above all, the beam scanning characteristic does not depend on three‐dimensional structures or complex loaded structures, therefore it is a promising technology for designing planar two dimensional beam steering array. Experimental results indicate that the impedance bandwidth of the antenna covers the frequency range from 13.3 to 16.7 GHz and the relative bandwidth is 22.7%. The accordance between the simulated and measured E‐plane radiation pattern of the antenna at three representative frequencies verifies the beam steering capability of the proposed antenna.

A novel bowtie‐shaped structure loaded with three concentric split rings is proposed for designing wideband reflectarray antenna with low optimizing complexity. The broadband characteristic of the proposed reflectarray element is realized by exciting multi‐resonances through the surrounded concentric split rings. Furthermore, a linear phase curve covering about 700° can be achieved by simply adjusting the flare angle of the concentric split rings. Based on the element, a prototype of the proposed reflectarray antenna with a diameter of 180 mm is simulated and measured. According to the measured results, the peak gain is 22.8 dBi at 10 GHz corresponding to an aperture efficiency of 42%. Besides, 3‐dB gain bandwidth of 28% (8.5–11.3 GHz) is obtained, and the cross‐polarization levels are below −25 dB for both principal planes.

A novel frequency beam‐scanning substrate integrated waveguide cavity‐backed wide slot antenna with a wide‐scanning angle and bandwidth is investigated. The wide slot etched on the metal substrate is not only the radiating element but also part of the feeding network, which makes the whole structure very compact. The experiment indicates that the design principle is correct. The measured results show that the antenna achieves an enhanced operating bandwidth of about 27% with the gain from 10.12 to 16.25 dBi and the corresponding scanning angle is from 12° to across the band. Good accordance is obtained between the simulated and the measured results.

Substrate integrated waveguide (SIW) is a planar waveguide structure, which offers the advantages of low profile, ease of fabrication, low insertion loss, and compatibility with other planar circuits. SIW end-fire antennas have drawn broad interests due to the potential applications in aircraft, missile, and radar systems. However, this planar structure suffers from narrow bandwidth due to severe impedance mismatch at the radiating aperture. Meanwhile, the narrow radiating aperture of SIW end-fire antennas also deteriorates the radiation performance. This paper presents a detailed review upon the most recent research efforts concerning the improvement of antenna performances. They are discussed and classified into three different categories from the aspect of polarization properties: horizontally polarized (HP), vertically polarized (VP) and circularly polarized (CP) SIW end-fire antennas. Some practical difficulties for the development of SIW end-fire antennas are pointed out and effective approaches are also provided. A wide variety of antenna examples are presented with respect to theoretical and experimental results.