Research On W-band Quasi-optical Isolation Technology

Traditional ferrite isolators and circulators often use microstrip,waveguide and other structures.The device size is comparable to the operating wavelength.When the frequency rises to the millimeter wave band,the device power capacity becomes the main technical obstacle.In addition,due to the limitation of saturation magnetization of ferrite materials,the operating bandwidth of traditional millimeter wave ferrite devices is not high.In order to meet the needs of broadband high-power millimeter wave transmission and transmission technology,a quasi-optical isolator technology with high power capacity and high bandwidth characteristics has been proposed.The quasi-optical isolator is composed of a series of quasi-optical devices such as Gaussian feed,lens,polarized grating,and Faraday rotator.The core device is the Faraday rotator.First,analyze and study the overall layout of the optical isolator.Determine the overall layout scheme quasi-optical network.Second,based on the basic characteristics of ferrite materials and the theory of electromagnetic wave transmission in ferrite materials.Using the equivalent transmission line theory,a fast matching study was carried out on a Faraday rotator with a multi-layer matching medium structure.And combined with three-dimensional simulation to optimize the design of multilayer thickness,the matching parameter design of broadband Faraday rotator is completed.Third,based on the propagation theory of Gaussian beams,theoretical calculations are performed on the parameters of the optical path.Combine with 3D electromagnetic simulation to optimize the overall optical path parameters.Finally,the Gaussian feed,polarization grating,lens and Faraday rotator are processed.Build a quasi-optical test system to complete the small signal parameter experimental test of the low-power quasi-optical isolation network model.The test results show that the working bandwidth of the W-band low-power quasioptical isolation network model is about 90GHz-98 GHz,the center frequency is 94 GHz,the rotation angle is 45o ± 1o,and the input standing wave is less than 1.2.The insertion loss of the Faraday rotator is between 0.3dB and 0.5dB,the isolation is greater than 30 dB,and the insertion loss is less than 1dB.It has the characteristics of wide frequency band,low insertion loss and high isolation.Test data agree well with the theoretical design calculations.The accuracy of the multi-layer medium matching algorithm and quasi-optical path calculation method used is verified.The thesis provides a working basis for the design optimization of the subsequent W-band high-power quasi-optical isolation network model.