Research And Application Of Active Phased Array Based On Vivaldi Antenna

With the growing development of the modern radar,the phased array radars have to meet the requirements of wideband operation and wide airspace coverage.By this means,the radar antennas need to work with a wide frequency band and a wide beam scanning angle.The Vivaldi antenna,with the excellent performance of wide frequency band,wide beams,and low cross polarization,becomes one of the important research topics for highperformance active phased array antennas.In this thesis,study on ultra-wideband and wideangle scanning phased array is proposed for engineering projects.The main research content can be divided into the following three parts:1.Study of the Vivaldi antenna element: A conventional Vivaldi antenna element is designed with wideband and wide beam radiation characteristics.And the deterioration of the gain flatness which caused by the metal floor is analyzed.Another Vivaldi antenna element with slot loading is designed to improve the gain of the antenna in low-frequency and the gain fluctuation over the frequency band.The measurement results verify that the antenna has a good impedance matching and radiation characteristics over the frequency range of 4.5-11.5GHz.2.Design of wide band and wide scanning angle phased array based on single-sided Vivaldi antenna: The necessity of the ‘small array' method for the design of large active phased arrays is expounded in this section.A T-shaped metal structure is used to perturb the high-order mode electric field and successfully suppress the scanning blindness.A 5 × 8array is designed and fabricated.Based on the measurement comparison,the gap caused by the assembly error deteriorates the performance of the array and the indium sheet is an effective improving method.The measured results agree well with the simulation.The element in the array center has a good active impedance matching and wide beam active pattern performances,but it has the problem of high cross polarization.3.Design of a large active phased array based on double-sided Vivaldi antenna: A large active phased array antenna working in the X-band is designed for the radar system.Two hundred elements are arranged in a caliber with a triangular grid array to reduce costs.A double-sided Vivaldi antenna with low cross polarization is used as the unit cell,and a 5 × 8array is designed.The radiation performance of the element in the array center is simulated and measured.The structure of the entire array is improved and the 6 × 12 array is measured.The measurement results show that the active VSWR of the active phased array is lower than2 in the 8-12 GHz frequency band.The beam-width of the active pattern is larger than 100 °in the 8-10 GHz,and larger than 60 ° at 12 GHz.The gain of the active phased array is greater than 24.3d Bi and the loss of the scanning gain is less than 4d B,which meet the design requirements.The active phased array has been successfully applied to the radar system.