The Design Of The Antenna For Wideband Direction Finding System By Comparing Amplitude And Phase

A direction finding system by comparing amplitude and phase is studied in this thesis. This kind of direction finder has several advantages, such as fast and accurate direction finding and high anticlutter ability. The antenna and mode forming network for direction finder are designed and measured in this thesis. The experimental result shows good agreement with the simulation result.Firstly, the principle of direction finder by comparing amplitude and phase is studied. Based on this principle, the direction finder's antenna and feed network is given, which contains two parts: four arms sinuous antenna and microwave mode forming network. Secondly, further study about four arms sinuous antenna is carried out. The geometry structure and capability of antenna are analyzed and a four arms sinuous antenna which works at 0.4~2.0GHz has been designed. The optimized geometry parameters of the antenna are gained through electromagnetic simulation .Then the VSWR and radiation pattern is measured. The experimental result shows good agreement with the simulation result. Thirdly, the design of microwave mode forming network is carried out. Through the analysis of the four arms sinuous antenna'work-modes, a dual polarized microwave mode forming network is proposed. Two primary components of the network are designed: ultra-band orthogonal directional coupler and orthogonal phase shifter. Multi-sections offset strip coupled-line is adopted in the design of the directional coupler which has been realized and measured. The simulation result of phase shifter is presented in the thesis. In the end, the direction finding capability of this system is analyzed.