Design And Experimental Study Of Superconducting Filter Based On SRR Structure

In recent years,electromagnetic metamaterials have attracted the attention of researchers because of their unique electromagnetic properties.Since the SRR(Split Ring Resonator)structure has been proposed,it has been used in various interdisciplinary fields because of its unique electromagnetic characteristics,SRR structure has also been applied to microwave devices soon.In microwave technology,the filter is a very basic but very important microwave device.The filter can select or filter out electromagnetic waves of different frequencies according to actual needs.Researchers have found that the SRR structure can play a variety of filtering effects,which can be used as the main structure of the filter and can also be used as an additional structure of the filter.The SRR structure has the characteristics of subwavelength resonance,and the filter loaded with the SRR structure can be miniaturized.However,due to the large loss of SRR,it limits its development and application in microwave planar circuits.The research content of this paper is to load the SRR unit into the high temperature superconducting microwave circuit,effectively apply the SRR structure to the planar microwave circuit,and design a superconducting filter based on SRR structure,which can not only exert the electromagnetic characteristics of the SRR structure,but also make use of the low loss characteristics of the superconducting material to make up for the large loss of the SRR structure.This paper is arranged as follows:Firstly,the concept of artificial metamaterial is described.The application of SRR structure in microwave circuit is listed.Then the principle and application of high temperature superconducting filter are explained.It is proposed that the combination of the two can complement each other.Secondly,the design requirements of the filter are proposed,and the simulation software is used to simulate the filter.Based on the design of a single SRR structure,the relationship between feeder position versus external quality factor and the relationship between SRR structure distance versus coupling coefficient are studied.According to the requirements of the filter,the appropriate coupling matrix is selected,and the required external quality factor and coupling coefficient are determined.The relative position of the SRR unit in the filter is determined.The simulation model of the filter is established,and the design index of the filter is achieved through simulation optimization,which proves the feasibility of this design method.Then,a high-temperature superconducting filter based on SRR structure is fabricated.The sub-wavelength resonance of SRR structure aid in the compact design of filter.The low-temperature test system is used to test the filter.The measured results of the filter have good consistency with the simulated results and show good band pass characteristics,the center frequency of the filter measured at 70 K is 2.515 GHz,the fractional bandwidth is 2.14%,the rectangular coefficient is 1.22,and the insertion loss is 0.1 dB.Finally,on the basis of the superconducting filter based on SRR structure,the SRR-based tunable superconducting filter is designed by simulation.