Research On Ku-band Rotman Lens Multi-beam Antenna

Nowadays,with the development of science and technology and the people's increasing demand for convenience of life,multi-beam antennas have been widely used and developed rapidly in civil fields such as 5G communication,auto driving,and remote sensing.Rotman lens is a commonly used multi-beamforming network with multiple input ports and output ports,and because its design is based on the principle of equal optical path,so the Rotman lens multi-beam antenna has a wide frequency band and the beam directions will not change with frequency changes.And because of its low production cost and it is easy to design,it has been used in the fields of communication,electronic reconnaissance,etc.and in various types of radars.First of all,this article elaborates on the basic principles of Rotman lens,analyzes its design equation,gives the design method of Rotman lens and analyzes the problems that need to be considered in the actual design,which lays the foundation for the actual design.Secondly,this article takes the Rotman lens multi-beam antenna in the form of a microstrip as an example.Starting from the analysis and determination of variables,the modeling and corresponding simulations are gradually carried out.Finally,a microstrip Rotman lens multi-beamforming network with a center working frequency of 15 GHz,7beam ports,8 array ports,and a maximum scanning angle of 32° is realized.The simulation results show that the amplitude fluctuation range of the array ports is within±2.5d B.The average value of the phase increment(decrement)is about 101°,69°,36°,and 0°,and the measured data are consistent with the simulated data.Then a rectangular microstrip antenna array and a microstrip Rotman lens multi-beamforming network were used for joint simulation.The results showed that the beam directions were ±31.4°,±21.2°,±10.4°,0°,and the beam gain was about 12 d Bi.Subsequently,in view of some of the problems in the previous part,the design of the Substrate Integrated Waveguide(SIW)Rotman lens multi-beam antenna was carried out.Among them,using the principle and characteristics of SIW,the design of tapered microstrip line-SIW conversion structure,unequal width SIW phase shifter,and 4-slot SIW slot antenna array is completed.And a method of modeling SIW using script is proposed,which simplifies the modeling process.The finally realized SIW Rotman lens multi-beam antenna has a center working frequency of 15 GHz,with 9 beam ports,10 array ports,and 8 virtual absorption ports.The simulation results show that the beam directions are ±35.0°,±25.9°,±17.3°,±8.8°,0°,the beam gain is about 20 d Bi,and the multi-probe spherical near-field antenna test system is used to test the real object,and the measured data is more consistent with the simulated data.Afterwards,a brief study on the multi-port simultaneous feeding which is aimed at reducing the sidelobe was carried out and certain results were achieved.At the end,the research achievements and significance in the design,analysis and modeling of the two forms of Rotman lens are summarized,and the subsequent improvement work is prospected.