Double‐layer metasurface‐based low profile broadband X‐band microstrip antenna

Abstract

In this paper, a novel technology based on double‐layer metasurfaces is proposed in order to broaden the bandwidth of microstrip antennas, which has been verified in X‐band linearly polarised and circularly polarised antennas. Referring to the conventional metasurface antenna that employs slot‐coupled feeding, these designs add an extra metasurface between the radiation patch and the ground plane so as to establish dual resonance modes, TM10 and TM20. Following the adoption of the composite right/left‐handed transmission lines principle, this technique aims to adjust the propagation constant in the right‐hand region by introducing parallel inductors and capacitors to widen the dual resonant frequencies' interval, thereby realising a broadband antenna. In addition, the interlayer metasurface may also be utilised as a director to balance the E‐field of the radiation patch. A linearly polarised double‐layer metasurface antenna with a size of 0.8×0.8×0.058λ0 (wavelength in free space at the centre frequency) is filled with F4B substrate with a dielectric constant of 2.2. It finally realises an impedance matching bandwidth (VSWR≤2) from 8.41 to 11.67 GHz, occupying about 32.47normal% of the centre frequency. This circularly polarised antenna attains both an impedance matching bandwidth of 32.44normal% (i.e. 8.29–11.5 GHz) and an axial‐ratio bandwidth of 19.72normal% (i.e. 9.6–11.7 GHz).

A compact broadband and high-gain metasurface antenna loaded with meander-line

“…Metasurface (MS) features the unique characteristics of CRLH material, the MS-based antenna has the capability to broaden the impedance bandwidth (BW) [12,13,14,15] and axial ratio BW for linearly and circularly polarized antenna [25], respectively, which has drawn lots of attention in the antenna design field. Despite this, the radiation aperture for the metasurface antenna (MSA) is still large, the inevitable grating lobes and strong EM coupling would occur, which is not beneficial for its application in dense arrays [16,17,18]. Therefore, how to realize a broadband high-gain MSA while maintaining a compact antenna aperture is very meaningful and necessary.…”

“…The other way to minimize the MSA is to improve the inter-element equivalent capacitance with the aid of some technical approaches [15,16,21,22,28,29,30]. For instance, reducing the gap distance between the MS units, a single-layer tightly coupled MSA with a radiating aperture of 0.73𝜆 0 × 0.73𝜆 0 (𝜆 0 represents the free-space wavelength at the center frequency) and impedance BW about 28% is achieved in ref.…”

“…Besides, the integration of the doublelayer MTS, outlined in ref. [16], featuring an aperture coverage of approximately 0.93𝜆 0 × 0.93𝜆 0 , facilitates the preservation of an impedance BW of 39.8% and peak gain 8.7 dBi In ref. [21], a non-uniform MSA is proposed , which realized 0.49𝜆 0 × 0.46𝜆 0 antenna aperture and 21.6% BW with a peak gain of 7.7 dBi.…”

Millimeter-Wave Broadband MIMO Antenna Using Metasurfaces for 5G Cellular Networks

“…Due to the exotic features, an appropriate combination of metasurfaces has been found to enhance the MIMO antenna performances such as isolation, gain, and bandwidth. For example, by placing a metasurface above or below of patch resonator, the antenna performance has been reported to enhance markedly [2,11,12,13,14,15,23]. The mechanism for enhancement of the antenna performance is due to the formation of surface wave resonance that creates surface wave propagation along the metasurface for extra resonance [2].…”