Research Of Negative Group Delay Circuit Based On Suspended Coplanar Waveguide

With the rapid development of a new generation of wireless communication technology,communication systems have put forward higher requirements for signal transmission quality.Among the indicators of communication systems,group delay is an extremely important technical indicator,which reflects the signal phase dispersion of the circuit.Group delay distortion will cause signal distortion,cause inter symbol crosstalk,and worsen the signal-to-noise ratio of the system.As a compensation method of group delay,negative group delay(Negative Group Delay,NGD)circuit shows strong competitiveness in meeting the requirements of contemporary 5G low delay and realizing high-performance wireless communication system.It shows great application potential in many application fields,such as improving microwave device performance,increasing feed-forward power amplifier efficiency,optimizing phase array antenna and so on.In this paper,by summarizing the existing negative group delay devices and circuits at home and abroad,and combining the advantages of the new suspended coplanar waveguide structure,such as low loss,high Q value,low cost and easy integration,two kinds of distributed negative group delay circuits and a power divider with negative group delay characteristics are proposed.The work is summarized as follows:Firstly,a low insertion loss NGD circuit based on suspended coplanar waveguide is proposed.The circuit is mainly based on the signal interference technology,and realizes the negative group delay characteristic of the circuit through the phase shift difference produced by the two transmission signals during the transmission process.The whole circuit presents a symmetrical structure,and its working principle is described by using odd and even mode parameter analysis method to reveal the influence of the parameters of each part of the NGD circuit on the circuit performance index.Then the simulation results are given to verify the rationality and correctness of the designed circuit.The working center frequency and negative group delay value of the NGD circuit can be controlled by adjusting the relevant parameters of the circuit,which improves the flexibility of the circuit application.In addition,due to the appearance of the grounding mode of the suspension structure,the circuit based on this structure has self packaging characteristics,which effectively reduces the radiation loss of the circuit and the insertion loss of the signal in the transmission process,which has the incomparable advantages of the traditional structure.Secondly,a self-matching NGD circuit based on suspended coplanar waveguide is proposed.The circuit mainly uses the method of etching U-shaped defects on the suspended coplanar waveguide transmission line to realize the negative group delay characteristic of the circuit,and realizes the self-matching effect of the circuit by paralleling the stub matching line at the center conduction band,The entire circuit adopts a purely distributed structure design.Compared with the traditional NGD circuit,it does not need to introduce any lumped components,and the proper working state of the circuit can be selected by adjusting the defect size.Compared with other current NGD circuits,it has the advantages of simple structure,small size,and low loss.Finally,a power divider with negative group delay based on suspended coplanar waveguide structure is proposed.This power divider is designed on the basis of the defect type self matching NGD circuit,which achieves the negative group delay effect as well as the power distribution.The circuit structure adopts an integrated design idea,By replacing one end of the transmission path of the power divider with an NGD circuit,the two branches of the power divider have the characteristics of positive group delay and negative group delay respectively.The design of the circuit structure simplifies the complexity of traditional passive device design,and has important reference significance for future multi-functional integrated circuit design.