Design And Implementation Of An X-band Microwave Circulator

As a kind of important nonreciprocal microwave device, ferrite circulator is often used in radar system because of its forward transmission and reverse isolation characteristics. It can solve the problem of connecting the transmitter and receiver to the same antenna. In aviation, aerospace, marine, electronics, communications,medical and other fields, the circulators have been widely applied.Considering the actual demand, this paper chooses X-band waveguide junction circulator for the study. Firstly, the design index of the waveguide junction circulator is put forward, and the related theory of the waveguide junction circulator is introduced from the ferrite materials, network analysis, field analysis, and equivalent circuit, which provides important reference for the later design and analysis. On the basis of this, the waveguide junction circulator is designed by using the disc-shaped impedance transformer, then the circulator is designed by using two partial height triangular ferrite posts, and the triangular impedance transformer is used to realize the impedance matching of the circulator, which solves the shortcomings of insufficient bandwidth. In order to make the structure compact, and the processing error can be adjusted, the T-Y structure and three screws tuner are adopted. The design scheme and calculation model of the selected design scheme are optimized by HFSS software, and the basic device size of the circulator is analyzed and determined. In the mechanical design of the waveguide junction circulator, the assembly step is introduced. The waveguide cavity, the matching block and the assembly step are integrated into the structure, which reduces the difficulty of processing and improves the assembling efficiency. At the same time, the magnetic field hole is trapped in the matching block, which effectively reduces the volume of the circulator. And then use the SolidWorks software for waveguide junction circulator processing drawing, and finally fabricated the circulator and completed the test.The test results show that the X-band waveguide junction circulator designed in this paper has excellent performance. In the 9.1 GHz?10.5GHz frequency band, the indexes meet the system requirements (insertion loss <0.3dB,isolation>20dB,VSWR<1.25).