Design Of A K-band Wide Band Beam Scanning Antenna Based On Fractal

Scanning antennas are widely used in radar and communication systems.The traditional beam scanning antenna works mechanically,which has poor stability and scanning speed.The new electric beam scanning antenna consists of phase scanning antenna and frequency scanning antenna.The former is widely used in military fields but it requires high power and high cost.And the latter has the advantages of small size and low cost,so it is suitable for civilian fields.A novel fractal-based wideband frequency scanning antenna is designed in this paper according to the scanning principle and fractal theory.The fractal pattern is applied in the microstrip array antenna.Because of the self-similarity and space filling characteristic of the fractal structure,the antenna improves the bandwidth and gain problems caused by return loss of the microstrip array antenna.A 20% bandwidth can be achieved and scanning range is from-45 ° ~ +40 °.The measured results verify that the fractal structure can help the antenna to increase bandwidth,scanning range and gain.It is of great significance for the research and application of frequency scanning antennas.Based on the electromagnetic theory,two kinds of antennas are designed: conventional rectangular patch microstrip array and quasi-Minkowski fractal microstrip array.The research work is as follows:(1)The radiation principle and frequency scanning characteristics are studied.The electromagnetic performance of the antenna is expounded.The design principle of substrate integrated waveguide structure and matching circuit are introduced.(2)Two microstrip array frequency scanning antenna models are designed and analyzed.The feed structure adopts SIW technology,and the parabolic structure is designed to be integrated into the substrate,which helps to realize low profile and high integration.The fractal pattern is applied in antenna to increase bandwidth,gain and scanning range.(3)The electromagnetic characteristics of the frequency scanning antenna are studied,mainly focusing on the analysis of scanning characteristics.The characteristics of the frequency scanning antenna are analyzed from four aspects: the scanning angle range,the symmetry of the scanning angle,the linearity of the scanning angle and the gain variation.The influence of fractal structure on the electromagnetic characteristics of the antenna array is studied.The measured results verify the validity of the proposed antenna.(4)The application of frequency scanning antennas in spaceborne is studied.By modeling and simulation in the full-wave analysis software HFSS,the performance of thermal deformation on the antenna is simulated and analyzed from the variation of gain and side lobes.Finally,measures to deal with thermal deformation is proposed in this paper and it provides a reference for its application in spaceborne environments.