Study On Dielectric-covered Substrate Integrated Waveguide Slot Antennas

The recently developed substrate integrated waveguide(SIW) has attracts intensive attentions due to its advantages of high Q-factor, low insertion loss, mass-producible and integrated easily with other planar circuits. However, many problems remain unsolved for design of dielectric-covered SIW slot arrays. In this thesis, we take a further study of SIW longitudinal slot arrays including dielectric-covered slot element, planar arrays, conformal arrays, the optimization design of dielectric covers, as well as their applications in monpulse and scaning arrays.Firstly, the basic characteristics of SIW structure are investigated and its equivalence with dielectric-fillled rectangular waveguide is introduced. The Green’s functions theory of stratified planar media is employed to conduct a general multilayer-covered slot element model. Then the Method of Moment(Mo M) is performed for the accurate evaluation of the characteristics of the slot element. The effects of the dielectric covers are also investigated;Secondly, the design method of planar slot arrays is studied. To overcome the previous nonrobust and numerically unstable approach for mutual coupling evaluations, an improved space-domain approach is proposed with the help of the discrete complex image method(DCIM), rendering an efficient and accurate evaluation of mutual coupling possible. Then the classic Elliott’s method originally proposed for an air-covered slot array is extended for a general multilayer-covered slot array, and several design examples for very low-sidelobe applications are performed;Then, the optimization design of dielectric covers is done with use of the Genetic Algorithms(GA). A GA-based general approach is proposed for the optimization of gain, sidelobes and bandwidth of the antennas, which is automatic, robust and comparable for complex structures. This method is validated by comparing with the available methods from open literature as well as full-wave simulations and experiments. Some interesting and exciting phenomena are observed which may find applications for waveguide transverse slot arrays and inclined slot arrays;Two typical applications of SIW slot arrays, namely the monpulse antenna and scanning antennas, are then introduced. We proposed a new compact two-layer structure for monpulse SIW slot arrays. A novel compact asymmetrical power divider and a compact comparator are both proposed, and then a 20×20 monpulse SIW array is designed. A SIW-microstrip hybrid Rotman Lens is fabricated and measured, and then a 10×10 scanning array is designed;Finally, the cylindrically conformal slot array is studied. The design equations for sectoral waveguide slot array are derived and an iterative design procedure similar to the planar case is then outlined. Then, an improved method is proposed to evaluate spatial-domain mixed potential Green’s functions accurately both in the near and far field without any special treatments along the axial line. Thus, the accurate calculation of mutual coupling between slots in cylindrically conformal slot arrays is available. Several array examples are provided to validate the proposed design method. Besides, the pattern synthesis method, phase compensation scheme and cylindtrical power divider for sectoral waveguide slot array applications are also researched and discussed.