Research On Feed Antenna For Active Milimeter Wave Imaging

In recent years,the development of millimeter-wave technology is very fast,the use of millimeter-wave can penetrate the characteristics of the fabric,you can use the millimeter-wave imaging system to detect hidden items under human clothing hidden items,mainly used in airport security and coastal anti-smuggling and other fields.Millimeter wave imaging system is mainly divided into active imaging system and passive imaging system.The active millimeter-wave imaging mechanism is different from the passive millimeter-wave imaging,which requires the feed antenna to radiate electromagnetic waves to the measured target,receive the electromagnetic waves reflected from the target,and reconstruct the image so as to conduct security identification.Compared with passive millimeter-wave imaging,active millimeter-wave imaging can obtain more information about the target being examined,and has lower requirements on the target's environment.Moreover,3d target imaging can be achieved.In millimeter-wave imaging system,the performance of the feed antenna is directly related to the imaging resolution of the system.Therefore,this paper focuses on the feed antenna of the active millimeter-wave imaging system.In order to reduce the complexity of the feed antenna and reduce the cost of the system,it is required that the feed antenna be integrated with the millimeter wave transceiver module or radiometer circuit.Based on the detailed analysis of millimeter wave imaging technology development present situation at home and abroad,because of the traditional microstrip patch array antenna bandwidth is narrow,and the antenna radiation pattern changes over the frequency,we design a 7?8 cell microstrip patch plane array antenna which is easy to be integrated and fed by substrate integrated waveguide.In order to reduce the sidelobe level of antenna radiation direction pattern,the Taylor amplitude distribution is realized by changing the width of patch element and designing the same-phase unequal-amplitude feeding network.Finally,the reflection coefficient of the antenna in the 74.2-81 GHz frequency band is less than-10 dB,and the antenna gain is more than 20 dB in this frequency band,and the sidelobe level is less than-20 dB.The maximum radiation direction of the antenna does not change with the change of frequency.In order to form focal plane scanning array,the end-emitting antenna is also studied.The designed Vivaldi antenna loaded with ZIM(zero refractive index material)has a reflection coefficient less than-15 dB in the frequency band of 60-110 GHz,and the antenna gain is more than 12 dB in this frequency band,and the sidelobe level is less than-10 dB.In addition,the Fermi tapered slot antenna was also studied.Under the condition that the antenna length is consistent with the Vivaldi antenna and the width is smaller,the reflection coefficient in the 60-110 GHz frequency band is less than-10 dB,and the antenna gain is further improved,which is more than 15 dB in this frequency band.