Research On The Design And Simulation Of 77GHz Substrate Integrated Waveguide Slot Array Antenna

In order to make driving safer and more comfortable,kinds of driving assistant systems have been developed.Radars and other sensors are employed in these assistant systems to perceive the traffic information around the car.The 77 GHz millimeter wave radar has the advantages of small size,long detection distance,high resolution,strong penetration and not affected by light conditions.It can work all day and all-weather,which is the main development direction of automotive radar.Substrate Integrated Waveguide(SIW)is a kind of transmission structure with the advantages of traditional metal waveguide and planar microstrip.It has the characteristics of low loss and large power capacity of metal waveguide,and also has the microstrip's advantages like small size,low cost,easy processing and integration,and easy to realize miniaturization and planarization in circuits.The slot array antenna based on this structure has the advantages of high gain,high efficiency,low loss and easy to achieve a shaped beam,which has a broad development prospect in radar and communication applications.In this paper,77 GHz millimeter-wave radar transmitting antennas based on the SIW slot antenna and SIW feeding network are researched and simulated using HFSS(High Frequency Structure Simulator).The main works of this paper are as follows:The linear slot array is designed.Firstly,based on SIW equivalent theory,an equivalent small rectangular waveguide array model is established.The slot characteristic parameter curve is extracted and fitted in the mutual coupling environment.By comparing with the array synthesis results,the initial design value of slot linear array is obtained.Then,parametric studies of main design parameters are carried out for the further optimization of the linear array.The designed linear array with low sidelobe and narrow beam on H plane is obtained,which can be used as the sub-array of plane array in the next step.The SIW feeding network and plane array is designed.Firstly,the vertical transition between standard rectangular waveguide and SIW is designed.Then two kinds of SIW power divider are designed.The first is the tree-shaped power divider,which is composed of L-junctions,T-junctions and Y-junctions.The low sidelobes of the array is realized by the tapered output amplitude of the power divider.Then an improved feeding network based on the traditional tree feed network is proposed.By integrating the feeding port in the idle area of the power divider,the size of the feeding network is reduced and the space utilization is improved.The simulation results show that the beamwidth of E-plane and H-plane is 13.9° and 9.7° respectively,the sidelobe suppression level is-25.5dB and-27.6dB respectively,and the gain at 77 GHz is 23.6dBi.The second one is a double-layer coupled feeding structure power divider.When designing the coupled waveguide,the characteristic parameters of the coupled slot are extracted by using a small array model,and the coupled waveguide with unequal output is designed as the power divider of the array.The simulation results of the coupled feeding array show that the beamwidth of E-plane and H-plane is 14.9° and 9.2° respectively,the sidelobe suppression level is-30 dB and-24.5dB respectively,and the gain at 77 GHz is 23.4dBi.Finally,the error analysis is carried out to test the tolerance of the antenna.The two kinds of planar array antennas all have good performances such as low sidelobes,narrow beam and high gain,which are suitable for millimeter-wave automotive radar application.