Design Of Microwave Waveguide-to-Microstrip Transition And Filtering Antenna

With the rapid development of millimeter-Wave technology,the HMIC and MMIC has been widely utilized in Radar communication,guidance and other systems.Due to its small size,the microstrip transmission line is more flexible in design than the metal waveguide,and has been widely used in millimeter-Wave circuits.However,at present,the input and output ports of many millimeter wave experimental equipment are in waveguide form,so the transition of these two structures is necessary in microwave/millimeter wave system.The common waveguide-to-microstrip transition technologies include ridge waveguide transition,probe transition,and antipodal finline transition.This paper mainly focuses on the theoretical analysis and simulation design of probe transition and antipodal finline transition.Finally,the transition structure of E-plane probe in W-band was fabricated and measured.The measured results show that the insertion loss of the structure is better than 0.65 dB within 74-107 GHz and the return loss is better than 11.8 dB,which meets the practical application.In communication systems,a cascade filter is usually utilized behind the antenna to select a specific frequency and suppress the out-of-band radiation.In order to realize miniaturization of RF front-end system,these two devices are usually designed together.Based on the theory of filtering antenna,an aperture-coupled high gain filter antenna is designed.The proposed antenna has no additional filter structure.By coupling the symmetrical short-ended stubs in the feeding network and U-shaped slots in the ground plane,the out-of-band radiation zero points are generated,which results in the filtering characteristics in a wideband range.Without introducing the insertion loss of filter directly,the proposed antenna obtains a relatively higher gain.Based on the proposed filtering antenna,a duplex antenna with filtering characteristics is designed in this paper.The duplex antenna shows two operation channels of 3.67-4.03 GHz for transmitting and 4.11-5.01 GHz for receiving with a high gain performance over a wideband frequency range,which realizes the integrated design of the duplex and filtering antenna and effectively simplifies the architecture of RF system.