Research And Design On X-band Microstrip Endfire Array Antenna With Low Sidelobe

At present, with the capacity of all-weather and all-time, microwave imaging techniques have been widely applied in the field of remote sensing, surveying and mapping, and military reconnaissance. The resolution of real aperture radar imaging technology is limited by the antenna aperture. But the microwave staring correlated imaging can obtain great image quality of high transverse resolution breaking antenna aperture diffraction limit, which will have wide application prospects and important research value.The microwave staring correlated imaging system works on a tethered balloon platform of high altitude. Characteristics of small size, small windward area, wide band, low sidelobe and high gain are required in the antenna design because of the special working circumstance of the imaging system. In consideration of the fact that familiar antennas and arrays cannot meet the requirements the imaging system raises, we put forward the structure of microstrip endfire antenna array which is of small windward area, thus ensuring the safety and reliability when the system works on the tethered balloon of high altitude. Therefore, it is in this program background that the research of this thesis is gradually carried out about microstrip endfire antenna and array with low sidelobe.Firstly, aiming at the requirements of small size and high gain, the small size microstrip endfire antenna of high gain is researched. By introducing metamaterials, this paper has designed a zero index metamaterial (ZIM) structure, with which a high gain microstrip Quasi-Yagi antenna has been researched and designed. The simulation and measurement results show the microstrip Quasi-Yagi antenna with ZIM has achieved higher gain than the conventional one of the same size, thus completing the design of the small size microstrip Quasi-Yagi antenna of high gain.Secondly, aiming at the requirements of wide band and low sidelobe, nature inspired computation combined with simulation of business software High Frequency Structure Simulator (HFSS) has been applied to research the synthesis of low sidelobe of two-dimensional microstrip endfire antenna array. At first, specific research has been done about the application of nature inspired computation in the synthesis of low sidelobe of array antennas. Then particle swarm optimization (PSO) combined with HFSS simulation has been applied to synthesize the sidelobe of two-dimensional microstrip Quasi-Yagi antenna array. Finally, the whole array has been simulated, fabricated and measured. And the results have verified this design effectively.Finally, aiming at the strong mutual coupling of two-dimensional microstrip Quasi-Yagi antenna array, this paper has researched the characteristics and effects of mutual coupling, then designed a corresponding decoupling approach and given the measurement results. At first, the mutual coupling characteristics of microstrip Quasi-Yagi linear array have been researched. Then it follows that the mutual coupling effects on input impedance and radiation pattern have been analyzed. At last, the decoupling design with metal fences on the two-dimensional microstrip Quasi-Yagi antenna array has been implemented. And the simulation and measurement results show significant improvement of radiation patterns and sidelobe reduction of the array with metal fences has been achieved compared with the array without metal fences, thus verifying this decoupling design effectively.