Design Of Wideband Metasurface Antenna Based On Characteristic Mode Theory

With the development of wireless communication technology,it has been deeply integrated with our daily life.Communication scenario requiring massive data transmission are constantly emerging,and massive data transmission has become an inevitable demand for high-quality economic and social development,As an important part of wireless transceiver equipment,antenna requires a wider bandwidth.Metasurface antenna not only has the characteristics of small size,easy integration,but also has excellent electromagnetic performance,which has a good application prospect in the field of wireless communication.Aiming at the demand of broadband antenna in the field of high-speed transmission,this paper carries out research on the problem of band broadening of metasurface antenna.Aiming at the problems of unclear electromagnetic performance optimization direction and low efficiency of full-wave simulation feedback tuning design process in antenna design,characteristic mode theory is used to guide antenna design,and the following work is mainly completed:(1)To meet the demand of miniaturization and integration of terminal equipment,the design of metasurface wideband antenna is studied based on the characteristics of patch antenna,such as low profile,small size and easy integration.Following the design concept of traditional metasurface antenna using repetitive periodic structure,starting from the guiding idea of multi-frequency resonance to expand the bandwidth,the characteristic mode analysis method is used to guide the optimization direction,and the rectangular patch with similar size is used to obtain the metasurface structure with broadband characteristics through multi-mode resonance at adjacent frequency.Then,the cross-polarization level of the metasurface is reduced by etching slit,and a new resonant mode is introduced to expand the bandwidth.Finally,a wideband metasurface antenna with low profile and small volume characteristics is designed.Measurement shows that the antenna works in the Ka band with a impedance bandwidth of 25.02%(30GHz-38.58GHz)and the realized gain is 8.35-11.3dB.The antenna size is only 1.423×1.423×0.029λ03(λ0 is the wavelength of the center frequency of free space),which well maintains the characteristics of small volume and low profile.(2)A wideband omnidirectional ring metasurface antenna is designed.From the definition of the mode weighting coefficient,according to the principle that the tangential component of the electric field applied by the excitation source should be parallel to the mode current as far as possible,the radial divergent electric field fed by the coaxial probe is used to excite the characteristic mode of the concentrically arranged ring metasurface.Two set of patches of different sizes are used to excite a variety of modes.46.45%(4.43-7.11 GHz)-lOdB impedance bandwidth is achieved.The antenna has the characteristics of omnidirectional radiation and good gain uniformity in the φ direction.