Study On Broadband Reflectarray And Transmitarray Antennas

Reflectarray antenna(RA)and transmitarray antenna(TA)combine the characteristics of parabolic antenna,lens antenna and phased array antenna respectively,with the advantages of high gain,simple feeding,easy processing,etc.They have wide application prospects in satellite communication,radar detection and other fields,and have become a research trend in the field of antennas in recent years.In this thesis,combined with the current development demand of broadband and high gain antennas for wireless RF systems,the current problems of narrow operating bandwidth and high array surface profile in the design of RA and TA are studied,and the TA and RA with broadband operating characteristics are designed respectively.The main research works of this thesis are as follows:1.Study on broadband TA based on two-layer metal-only structure.First,a two-layer metalonly TA unit cell with linear polarization rotation characteristics is designed,and the transmission amplitude of the unit cell is effectively improved by introducing metal post between the layers.At the same time,the bent slots structure is used to realize the miniaturization design of the TA unit cell.In order to improve the transmission band range of the unit cell,the combination of two sets of slots of different lengths effectively broadens the working band.In addition,on the design of unit cell phase shift,by changing the relative position of the slots in the unit cell,it has two relative states,both of which have 180° phase difference;then by changing the length of the slots,the two relative states have a continuous180° phasing range,thus realizing the broadband 360° phase shift of the unit cell.A 16×16scale broadband TA was designed using the proposed TA unit cell and fabricated for measurement.The measured results show that the proposed two-layer TA achieves a 1-d B gain bandwidth of 14.6%(8.2-9.5 GHz)and an aperture efficiency of up to 47.6%.Compared with other metal-only TAs,this design achieves sufficient phase adjustment range and good broadband operation characteristics with only two layers.2.Study on broadband RA based on multi-resonant microstrip patch structure.Firstly,the size of the microstrip patch is halved by using a metal sheet short circuit without affecting the resonant frequency of the microstrip patch unit cell.Second,based on the design idea of bandwidth expansion of multi-resonant mode,the microstrip patch of another resonant frequency is introduced by means of a common shorting sheet to achieve a dual resonant unit cell design.In addition,in order to further expand the bandwidth and extend the phase tuning range,a new resonant point is introduced by adding a grounded semicircular ring to form a microstrip RA unit cell with triple resonance characteristics.By optimizing the unit cell structure,the linear phase tuning range is nearly 800°.Using the proposed broadband microstrip unit cell,a 16×16 scale broadband RA is designed.Simulation results show that the RA has 23.9% 3-d B gain bandwidth and maximum 55% aperture efficiency,with good broadband operating characteristic,and the thickness of the reflecting surface is only 0.046 times the center frequency operating wavelength.