| Nowadays,wireless systems require high directivity and wide radiation range antennas to achieve a far propagating distance and a wide range coverage.The beam scanning antenna has a high directivity,and has the capable of controlling beam direction by frequency,mechanical,electronically component,special medium.The most widely used beam scanning antenna is the phased-array antenna.The phased-array antenna realizes beam scanning by using the phase shifters or attenuators.Meanwhile,the massive use of electronically components resulted in the phased-array antenna becoming expensively,bulky and complicated.Leaky-wave antennas can control beam direction by changing frequency,and have the advantages of high gain,simple structure,ease of integration,and low cost.So leaky-wave antennas have attracted wide attention of researchers.However,there are many problems when leaky-wave antennas applied in wireless systems.Firstly,the conventional leaky-wave antenna has a limited scanning range,and only realizes forward or backward radiation.Secondly,to obtain a wide beam scanning range,the leaky-wave antenna will occupancy a wide frequency range,which leads to leaky-wave antenna hard to apply in the wireless system where the scarcity of spectrum resources.In recent years,with the development of artificial electromagnetic materials,antenna technology is facing great opportunities.The applications of artificial electromagnetic material in the leaky-wave antenna have huge potential.Aiming at the application requirement of fixed-frequency beam scanning antenna,this paper research the application of artificial electromagnetic material to the leaky-wave antenna,a leaky-wave antenna with high scanning rate based on composite right/left-handed(CRLH)transmission line is proposed,and several fixed-frequency beam scanning leaky-wave antennas are proposed.Firstly,based on the substrate integrated waveguide technology,a fixed-frequency beam-scanning leaky-wave antenna with a simplified electrically controlled network is proposed.Then,based on rectangular waveguide with the reconfigurable high impedance surface,a fixed-frequency beam-scanning leaky-wave antenna is proposed and designed.1.By removing the end-cell error of finite-length CRLH-TL structure,an effective method to extract the accurate dispersion characteristics and the accurate transmission matrix of the composite left/right-hand transmission line is proposed.According to the proposed method,the accurate transmission matrix and the accurate equivalent circuit parameters of CRLH-TL are extracted,and the proposed method provides effective approach to designing CRLH leaky-wave antenna and reconfigurable CRLH leaky-wave antenna.2.A method to design high beam scanning rate CRLH leaky-wave antenna is proposed.According to the proposed method,several CRLH leaky-wave antennas with a high beam scanning rate,a wide scanning range is designed,fabricated and measured.3.A fixed-frequency beam-scanning leaky-wave antenna with a simplified electrically controlled network is proposed.Firstly,a CRLH leaky-wave antenna based on corrugated substrate integrated waveguide structure is proposed.The proposed antenna is ease of integration electronically components because it has two DC equipotential planes,and the cross polarization is quite low.The relationship between the equivalent circuit model and the physical structure is analyzed,and then an electrically controlled fixed-frequency beam scanning leaky-wave antenna is proposed.The proposed antenna has a simplified electrically controlled network,and a few number of varactor diodes.By adjusting the DC bias voltage,full-space beam scanning is obtained at a fixed frequency,while the gain of the antenna is stable,the scanning range is wide.4.The relationship between the propagation constant of the waveguide and the surface impedance of the high-impedance surface is proposed by analyzing the propagation characteristics of high-impedance waveguides.A method to achieve fixed-frequency beam scanning antenna based on high-impedance waveguide is proposed.According to the method,a fixed-frequency beam scanning antenna with high performance is designed. |
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