Design And Simulation Of The Ferrite Microstrip Circulator At Ku-band

In this paper, a micro-strip circulator by yttrium-iron-garnet(YIG) is designed which is working at Ku-band, and the simulation and optimization has been carried on. In general, the structure of the circulator is the strip line, however, with the rapid development of modern microwave integrated circuits, the circulator should be developed towards miniaturization and integration with the performance of low loss, wide frequency band, and meet the business requirements of low cost and batch production. Therefore, it is of great significance to study the micro-strip circulator.This paper mainly completed the following work.(1) The electromagnetic field theory, micro-strip line theory and related theories of circulators are analyzed and concluded that the electromagnetic wave in micro-strip line structure is the quasi-TEM waves, the derivation method of S parameters, load matching theory and its methods;(2) A preliminary structure of circulator is designed, which is working at Ku-band according to the theory and technology.(3)Two circulators simulation research of the design parameters and impedance matching are studied, the center frequency of circulator is decreased with the increasing of the center node radius, the film thickness, the strength of the magnetic field, the magnetization of external radius. besides, the wave port height and width respectively in 4H and 2w~8w with the coupling angle of 0.3 and the groove depth of the substrate thickness of 80% ~ 90% has a better round effect, a greater bandwidth will be achieved by using the exponential tapered line matching;(4) A practicality circulator is produced according to the design size combining with the vacuum coating and lithography process, and initial tests have been carried out. In this paper, the final design of a micro-strip circulator operating at Ku band is designed, the lowest insertion loss is 0.5dB, the largest isolation is 40 dB, the lowest voltage standing Bobbi is 1.05, the relative bandwidth is greater than 10%, and volume is smaller than 10mm×10mm×3mm, which meets the requirements of miniaturization.Thin film micro-strip line circulator designed in this paper, and related work of assembly and test is carried out. The conclusion of thin film circulator obtained in this paper is expected to be applied in the design of the miniaturization microwave ferrite circulator.