Research On Circular Polarization Slot Antenna Fed By Ridge Gap Waveguide

With the increased frequency of the microwave research,the traditional rectangular waveguide and microstrip antenna have a bad effect on the performance of the antenna due to processing problems and dielectric loss.Against this background,P.-S.Kildal proposed a kind of new transmission structure named gap waveguide.Its theory synthesizes the theories of traditional waveguides and microstrip lines and it also solve both the processing problems and dielectric loss.The ridge gap waveguide is composed of metal ridges,periodic EBG structures,and upper and lower metal plates.Because of the high impedance characteristic of the periodic EBG structure,the electromagnetic wave can only propagate along the metal ridge structure in the air gap between the metal ridge and the upper metal plate.As a pure metal structure,the ridge gap waveguide is relatively small in volume and can be machined in one body,which avoids the error caused by screw connection,and is easy to be miniaturized and integrated.In practical engineering applications,circular polarization antenna is favored because of its higher stability and stronger anti-jamming ability.Considering the broadband,circular polarization and low side-lobe design requirements of the antenna,two kinds of circularly polarized slot antenna elements based on the ridge gap waveguide are studied and designed according to the characteristics and advantages of the ridge gap waveguide structure.The circularly polarized slot array of ridge gap waveguide is formed respectively.Firstly,a circular polarized slot antenna element based on ridge gap waveguide in Ka band is designed.By means of the L-shaped metal ridge feed structure and the concentric circular slot with coupling branches,the antenna elements radiate circular polarized waves.Then,two kinds of planar antenna arrays are designed according to the specifications.Then,two kinds of planar antenna arrays are designed according to the specifications.Compared with the two designs,the first one is that the side-lobe energy is too high because of the large cell spacing.After analyzing the reasons,the second design scheme is put forward,which greatly reduces the side-lobe energy.Finally,the second design is adopted as a 2 × 2 antenna array.Secondly,a Ku-band low side-lobe antenna array based on ridge gap waveguide is designed,which is similar to the Ka-band circularly polarized antenna element.The array is a 16-element array.In order to satisfy the characteristics of low side-lobe,the array distribution adopts Chebyshev distribution.The overall performance of the antenna array meets the design requirements of the array.Finally,the circular polarization slot antenna array based on ridge gap waveguide with low side-lobe in Ku band is fabricated and measured.The reflection coefficient,realized gain and the axial ratio of the measured antenna are similar with the simulation results and the measurement errors is within the acceptable range.The feasibility of this antenna array scheme design is verified.