| With the rapid development of ultra-wideband(UWB)communication technology,UWB antennas have been widely used in the fields of EMC testing?satellite tracking system?transmitter feed and radar system because of high speed?high power capacity and ultra-wideband.The traditional horn has limited bandwidth due to the fact that the feed port waveguide presents a bandpass filter,so it is difficult to satisfy the requirement of the UWB system.In order to meet the demand,a double-ridged horn antenna is constructed by adding a ridged structure to the traditional horn feed waveguide.Because of the capacitance effect in the ridge waveguide,the cutoff frequency of the main mode in the waveguide is reduced and the cutoff frequency of the higher mode is increased,which expands the working bandwidth of the horn antenna.Monopulse radars play important roles in the fields of missile launch guidance?satellite surveillance?target tracking and positioning and satellite detection The performance of monopulse antenna directly affects the overall performance of the radar system and the accuracy of target positioning.In this paper.the wideband double-ridged horn antenna is studied,the circular polarization monopulse array antenna and planar broadband monopulse array antenna are designed according to the different requirements.The main research contents are as follow:1)A 2?18GHz wideband double-ridged horn antenna is designed.The horn antenna achieves the working bandwidth of 2?18GHz by using the structure of ridge waveguide feed and gradual ridge curves.In order to solve the common problems of pattern sag and gain drop in the high frequency band,the short-circuit plate structure with wedge-shaped structure and stepped shape is adopted at the end of the feed ridge structure.The antenna simulation and measurement results show that the antenna pattern at the high frequency point(18GHz)has great direction without sags in the orientation diagram,and the antenna gain is 15.67dB.2)A Ka band circularly polarized monopulse array antenna is designed.The antenna unit adopts the coupled slant slot feeding horn antenna to achieve circular polarization wave radiation,and the array antenna is composed of 12 one-in-two feeding horn units.The performance such as low sidelobe level?narrow beam and high puncture rate can be achieved by means of excitation amplitude weighting.In order to realize the miniaturization design,the radiation unit adopts the stepped horn structure,which reduces the height of the traditional horn by 40%.At the same time,the feeding network uses the rotational symmetry method,which effectively utilizes the spatial layout of the array antenna.The array antenna feed network with H-T waveguide structure and Magic T structure to realize sum and difference beam in the azimuth plane.The array antenna is in the range of operating frequency range of 35.6?3 6GHz,and the voltage standing-wave ratio of the difference port is less than 1.5,and the antenna gain is more than 22dB.The measured results of other antenna indexes are basically consistent with the simulation and meet the design requirements.3)In order to track and locate multiple targets,a planar wideband monopulse array antenna is designed.On the basis of one-horn antenna fed by waveguide,the antenna unit adopts one-in-four antenna fed by cavity coupled waveguide to achieve high gain radiation.The feed network realizes the radiation of the array antenna and beam?sum and difference beam in the azimuth plane and in the pitch plane through the combination of four different magic T structures.The antenna array adopts octagonal layout,and the antenna unit is stimulated by the same amplitudes and the same phases,so as to achieve the requirements of high gain and narrow beam.The antenna simulation results show that the gain is greater than 35dB and the half-power beam width is around 3.8° in the operating frequency range of 33?37GHz.The antenna performance index meets the design requirements. |
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