| With the growing demands of aerospace telemetry,tracing and control,traditional separate antenna reception systems,which adopt different sets of antennas for signals within different bands,can no longer satisfy the requirements.The proposed wide-band monopulse antenna system effectively reduces the antenna numbers and the costs of the system by utilizing one set of antennas to cover the four mainly used bands in TT&C including S\C\X\Ku bands.Based on the theory of wide-band monopulse antenna,the innovative work of the thesis includes the following four aspects:1)A tightly coupled array antenna integrated with a balun is designed.The antenna mainly consists of a microstrip T-junction,a stripline Marchand balun,a coupling patch,a radiation patch,a dielectric matching layer and resistors.The effects of key factors including the coupling patch,the resistors and the thickness of the dielectric matching layer on the VSWR of the antenna are analyzed.The simulation of a unit under two-dimensional master-slave boundary and the 15×1 array under one-dimensional master-slave boundary are completed.The simulation results show that the array obtain a VSWR less than 3 and a axial ratio less than1.1d B with a null depth of sum/difference beam over 35 d B.Besides,the physical test is completed,in which the VSWR is less than 3 in S band and less than 2.5 in C\X\Ku bands.The test result agrees with the simulation result and satisfies the targets.2)A kind of ultra-broadband power-division microstrip phase shifter is designed,which is mainly used to realize the combination of four constant-amplitude in-phase sub-array ports through wiring on both sides of the dielectric substrate.Physical tests show that the amplitude error of each port is less than 1.5d B and the phase error is less than 13° with the VSWR less than 2.4.The antenna basically achieves the target,while the performance deviation in Ku band exists.3)A ultra-broadband stripline Wilkinson power divider is designed,which is mainly used to realize the combination of four constant-amplitude in-phase microstrip power divider ports.The two groups of power dividers achieve the combination of sixteen constant-amplitude inphase ports together.The broadband stripline Wilkinson power divider is cascaded through a five-stage Wilkinson power divider to realize broadband working.Physical tests show that the amplitude error of each port is less than 1.3d B and the phase error is less than 13°,which agrees with the simulation results.The VSWR in S\C bands is less than 1.5 and less than 4 in part of X\Ku bands.4)Four groups of stripline sum-difference networks are designed,and the sum signal,pitch difference and azimuth difference are obtained from the networks respectively.The sumdifference networks,mainly composed of a two-stage broadband 90° phase shifter and a twostage three-branch broadband directional coupler,is realized with a double-layer stripline structure.Physical tests show that the VSWR is less than 2.3 in S\C\X\Ku bands.Besides,the phase error of each port in the sum-difference network is less than 10°,and the amplitude error of each power component is less than 1.5d B in most of the working bands,which basically agrees with the simulation result. |
