Microwave beam steering of planar antennas by hybrid phase gradient metasurface structure under spherical wave illumination

Abstract

To facilitate the microwave beam steering of planar antennas in both elevation and azimuth planes, a radially gradient quasi-transparent hybrid metasurface (RGHMS) structure is proposed. The circular aperture of RGHMS is comprised of two different phase profiles in the single structure. Half of the circular aperture introduces a gradient phase shift, whereas the other half provides a constant phase shift to the incident spherical wave. Since the obtained wavefront modulation for the beam tilting is realized using the combination of aforementioned phase profiles in a single metasurface (MS), it is considered as a hybrid structure. The proposed circular RGHMS with a radius of 1.2λ0 is placed at a height of 0.43λ0 from the feed antenna by considering the geometrical centers of RGHMS and antenna aperture coinciding with each other. The in-plane translation of the RGHMS modulates the wavefront of the incident wave, which results in 0° to 18° beam steering of planar antenna in the elevation plane. Moreover, in-plane rotation of RGHMS around the antenna axis facilitates the beam steering in the azimuth plane with a full 360° azimuthal coverage. The proposed structure is designed at the center frequency of 10 GHz and introduces uniform beam shapes with the gain of 12.3–14.3 dBi during the beam steering. The strategy of combining two different types of phase profile in a single MS eludes the requirement of the phase correcting lens, and thus can directly be illuminated through the spherical wavefront of antenna in the near field. Moreover, the microwave beam steering in both planes with fairly high gain and compact configuration is revealed.

Wideband beam-steerable configuration of metasurface loaded slot antenna

“…In summary, as compared to the configuration presented in Ref. , the proposed antenna structure is relatively thin providing wide operating bandwidth without compromising its beam steering properties in both elevation and azimuthal planes.…”

“…In the other words, in‐plane translation of the MS above the aperture of slot antenna modulates the phase of E y in the near field which results into beam steering in the elevation plane. Moreover, the phase distribution of E y of slot antenna in the near field is also found rotationally symmetric, hence in‐plane rotation of MS facilitates beam steering in the entire azimuth plane with full 360° area coverage. As mentioned above, the direction of main beam that is “θ t ” is also depending on the operating frequency “ f 0 ”, which will be discussed in the later section of this article.…”

“…Still, the bulky nature make these structures less attractive. Recently, authors were proposed a new kind of MS, that is a radially gradient hybrid metasurface (RGHMS) which was directly illuminated through the spherical wavefront of patch antenna . This structure was revealed a compact beam steerable configuration by eliminating the intermediate planar lens, as being utilized by other researchers previously.…”

A compact configuration of semicircular metasurface loaded slot antenna for beam steering application

“…To achieve compactness in the beam steering structures, the intermediate planar lens has been eliminated in refs. . In these structures, a radially gradient hybrid metasurface (RGHMS) was directly illuminated through the spherical wavefront of the source element and hence a compact beam steerable configuration has been achieved.…”

“…It was investigated that at an approximate height of 0.50 λ 0 from the aperture of antenna, the nonzero E y component of the antenna shows quite rotationally symmetric phase distribution. Hence, the RGHMS with the approximate aperture size of 4.5 λ 0 2 was safely placed at an approximate height of 0.50 λ 0 from the aperture of antenna to facilitate beam steering in both the azimuth and elevation planes . It was later realized that using slightly asymmetric phase distribution of the E y component of antenna in its close proximity, the more compact configuration with better beam scanning range in the elevation plane can be obtained while tolerating beam steering in the horizontal plane.…”