Research And Design Of Slow-Wave Substrate Integrated Gap Waveguide And MIMO Antenna

Gap waveguide has been proposed as a new transmission structure for microwave and millimeter wave applications in recent year.Gap waveguides use parallel AMC(Artificial Magnetic Conductor)and PEC(Perfect Electric conductor)plate as electromagnetic shielding structures.A wide electromagnetic bandgap can be formed between two plates without physical contact.The gap waveguide uses air as gap and the two surfaces do not need electrical contact leading to lower insertion loss and higher design convenience.Substrate integrated gap waveguide(SIGW)has many advantages,such as high integration,low profile and easy fabrication,due to its planar PCB technology.In recent years,the development of high performance microwave circuits has put forward higher requirements for the integration and miniaturization of microwave devices.Therefore,the study of gap waveguide and its miniaturization technology is of great value.On the other hand,MIMO technology is widely used in 4G and 5G communication systems because it can improve data transmission rate and channel capacity.Based on the requirement of miniaturization of communication equipment,designing MIMO antenna with miniaturization and high isolation in limited space has important engineering application value.Based on the design of gap waveguide and its miniaturization and MIMO antenna,the following works are carried out in this paper:Firstly,a novel substrate integrated gap waveguide is introduced in this paper.Based on the characteristics of high tolerance,less fringing field spreading and wide bandgap of the new half-height EBG(Electromagnetic Bandgap)structure,a novel SIGW with cutoff frequency of 20 GHz is designed.SIGW has many advantages,such as no physical contact,high integration and low loss.The proposed waveguide is based on triple layer substrates with a total height of 1.041 mm.The top and bottom layer is the double textures mushroom shaped EBG units.The middle layer,which is a substrate with no metal on the surface,is used to separate double textures mushroom unit cell as gap for easy manufacturing.The proposed SIGW is easy to fabricate and has high integration compared with metal waveguide.Secondly,a slow-wave SIGW is designed in this paper.Make full use of metallic via holes can improve the electric field effect and reduce the waveguide cutoff frequency,a miniature slow-wave SIGW is realized.The electric field is concentrated in the top and the gap layer with metallic via holes loading in the bottom layer,thus increasing the relative dielectric constant and the cut off frequency of the waveguide decreases from 20 GHz to 11.8 GHz.Therefore a size reduction of 41% of the lateral dimension is achieved with reference to that of the conventional SIW counterpart at the same cutoff frequency.At the same time,the normalized phase velocity of the waveguide decreases by 54.9%,which reduces the longitudinal size of the waveguide under a given electrical length.Thirdly,a miniaturized dual-port MIMO antenna for WLAN applications is designed.Based on the fact that the meandering monopole can reduce the overall size of the antenna and the semi-circular patch has high radiation performance,the miniaturization and high isolation MIMO antenna design is realized by involving a meandering line decoupling resonator connected to the ground.The antenna system can have good performances with a small structure which operating in 2.4/5.2/5.8 GHz bands for WLAN applications.High isolation between two ports is achieved without increasing the antenna size and profile.