Research And Design Of Antennas Based On Characteristic Mode Theory

With the rapid development of wireless communication technology,the application scenarios of antennas are diverse and complicated,which also puts forward a more differentiated demand for antenna performance.Using the characteristic mode theory to guide the antenna designs can improve efficiency and provide a simple and intuitive idea for the antenna design from a clear and concise physical understanding.Based on the above background,this paper focuses on the application of characteristic mode theory combined with emerging metamaterial technology and complementary antenna idea.The main work and innovation are as follows:（1）Combining characteristic mode theory with emerging metamaterial techniques,a new low-profile wideband linear-to-circular polarization conversion metasurface antenna for C-band satellite communication applications is designed.The design of metasurface units and the mechanism of generating circularly polarized waves are explained by using the equivalent circuit principle and characteristic mode analysis.Finally,the proposed antenna with a total size of 36 mm×36 mm×3.5 mm（about 0.65λ₀×0.65λ₀×0.06λ₀）was fabricated.The measured results show that the S₁₁bandwidth of the proposed antenna is39.25%（4.28 GHz～6.37 GHz）,and the 3 d B axial ratio bandwidth is17.77%（5.18 GHz～6.19 GHz）.This circularly polarized metamaterial antenna has a compact structure,wide impedance bandwidth and axial ratio bandwidth,indicating broad application prospects in the field of satellite communications.（2）Combining characteristic mode theory with the complementary unidirectional antenna idea,a novel method to suppress the back-lobe radiation and achieve unidirectional radiation patterns is proposed.Based on characteristic mode analysis,the simultaneous radiation of the electric and magnetic dipoles is realized by exciting and reconstructing the complementary current modes of the isosceles right triangular conductive slab.Compared with conventional complementary antennas which need two different radiating sources to realize the electric and magnetic dipole radiation individually,the proposed method reuses the radiating aperture and achieves the unidirectional endfire radiation with a front-to-back ratio greater than 20 d B by a single radiating aperture.The proposed method is applicable for other types of radiators tailoring the radiation patterns,which provides a unique perspective for the pattern control and customization of different radiation performances.