We study the coupling problem of two waveguide antennas using the design of a two-dimensional inhomogeneous impedance structure with a fixed reflected field. Since this structure enables electromagnetic compatibility ...We study the coupling problem of two waveguide antennas using the design of a two-dimensional inhomogeneous impedance structure with a fixed reflected field. Since this structure enables electromagnetic compatibility between antennas located on a plane, the behaviors of the electromagnetic field along the impedance structure are investigated. The method of moments is used to solve the integral equations and the numerical results are presented and analyzed. To reduce coupling between antennas, we need to take into account both the amplitude distribution of the field along the structure and in the openings of the antennas. In addition, while designing the structure, it is necessary to control the coefficient of decoupling.展开更多
Wireless communication systems which require flexibility and reconfigurability in antenna systems faces main problems like antenna performance, size, weight and cost. A wide band Frequency Reconfigurable Rectangular S...Wireless communication systems which require flexibility and reconfigurability in antenna systems faces main problems like antenna performance, size, weight and cost. A wide band Frequency Reconfigurable Rectangular Slotted Self Similar Antenna has been proposed in this paper. The rectangular slotted patch is repeated for two iterations at different scales and is separated by means of Radio Frequency Micro Electro Mechanical Systems (RF MEMS) switches in order to provide reconfigurability. The antenna can operate in three frequency bandsi.e. K-band, Ku-band and Ka-band by altering the states of RF MEMS switches. To avoid fringing effects and to improve antenna performance, quarter wavelength (λ/4) spacing is required between the antenna and the ground plane. However, a Reconfigurable Antenna requires different λ/4 spacing which is difficult to achieve using a common ground plane. So the Frequency Reconfigurable antenna is integrated with high impedance surface (HIS) like Electronic Band Gap (EBG) structures to suppress standing waves and surface waves with a unified profile thickness of 1.75 mm. The overall dimension of the proposed antenna along with RF MEMS Switch, feed element and HIS is about 8 mm × 8 mm × 1.75 mm. The simulated results of the proposed antenna reveal enhancement in antennas performance like Voltage Standing Wave Ratio (VSWR), Front to Back Ratio (FBR) and bandwidth when it is placed over HIS EBG. Also the radiation patterns of the proposed antenna when placed over EBG shows the suppression of side lobe and backward radiation.展开更多
Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural ...Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural fragility,and thermal instability.In this study,an innovative PyC@SiC_(nws)@SiBCN ceramic foam was fabricated via a two-step impregnation process,followed by polymer-derived ceramic conversion through pressureless pyrolysis.The effects of SiC nws content and pyrolysis temperature on microstructure,dielectric behavior,and microwave absorption were comprehensively investigated.Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces,and the optimal absorber exhibits exceptional performance with a minimum reflection loss of-58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz(covering the entire X-band)at merely 4.5 mm thickness.The three-layered coating structure composed of PyC,SiC_(nws),and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously,providing new insights into the structural engineering of ceramic foams for microwave absorbers.展开更多
文摘We study the coupling problem of two waveguide antennas using the design of a two-dimensional inhomogeneous impedance structure with a fixed reflected field. Since this structure enables electromagnetic compatibility between antennas located on a plane, the behaviors of the electromagnetic field along the impedance structure are investigated. The method of moments is used to solve the integral equations and the numerical results are presented and analyzed. To reduce coupling between antennas, we need to take into account both the amplitude distribution of the field along the structure and in the openings of the antennas. In addition, while designing the structure, it is necessary to control the coefficient of decoupling.
文摘Wireless communication systems which require flexibility and reconfigurability in antenna systems faces main problems like antenna performance, size, weight and cost. A wide band Frequency Reconfigurable Rectangular Slotted Self Similar Antenna has been proposed in this paper. The rectangular slotted patch is repeated for two iterations at different scales and is separated by means of Radio Frequency Micro Electro Mechanical Systems (RF MEMS) switches in order to provide reconfigurability. The antenna can operate in three frequency bandsi.e. K-band, Ku-band and Ka-band by altering the states of RF MEMS switches. To avoid fringing effects and to improve antenna performance, quarter wavelength (λ/4) spacing is required between the antenna and the ground plane. However, a Reconfigurable Antenna requires different λ/4 spacing which is difficult to achieve using a common ground plane. So the Frequency Reconfigurable antenna is integrated with high impedance surface (HIS) like Electronic Band Gap (EBG) structures to suppress standing waves and surface waves with a unified profile thickness of 1.75 mm. The overall dimension of the proposed antenna along with RF MEMS Switch, feed element and HIS is about 8 mm × 8 mm × 1.75 mm. The simulated results of the proposed antenna reveal enhancement in antennas performance like Voltage Standing Wave Ratio (VSWR), Front to Back Ratio (FBR) and bandwidth when it is placed over HIS EBG. Also the radiation patterns of the proposed antenna when placed over EBG shows the suppression of side lobe and backward radiation.
基金supported by the National Natural Science Foundation of China(Grant Nos.52102113,52231007)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2021160)the Creative Research Foundation of TSCM。
文摘Porous carbon-based microwave absorbers demonstrate significant potential due to their lightweight characteristics and tunable dielectric properties,despite persistent challenges including narrow bandwidth,structural fragility,and thermal instability.In this study,an innovative PyC@SiC_(nws)@SiBCN ceramic foam was fabricated via a two-step impregnation process,followed by polymer-derived ceramic conversion through pressureless pyrolysis.The effects of SiC nws content and pyrolysis temperature on microstructure,dielectric behavior,and microwave absorption were comprehensively investigated.Results demonstrate that heat treatment modulates the composition and multi-dimensional heterogeneous interfaces,and the optimal absorber exhibits exceptional performance with a minimum reflection loss of-58.4 dB at 11.0 GHz and ultra-wide EAB of 4.2 GHz(covering the entire X-band)at merely 4.5 mm thickness.The three-layered coating structure composed of PyC,SiC_(nws),and SiBCN enables effective regulation of impedance matching through dielectric gradient distribution and induces multiple interfacial polarization losses synchronously,providing new insights into the structural engineering of ceramic foams for microwave absorbers.
