Research Of Microwave Components With Flat Negative Group Delay Characteristics

Negative group delay(NGD)characteristic refers to that phase is the positive rate of change with the frequency.This characteristic has been widely applied in microwave communication systems and radio frequency components,such as compensating phase shifting of oscillators,enhancing efficiency in feed-forward power amplifiers,optimizing beam-squinting of series-fed antenna arrays,increasing the phase-difference bandwidth of phase shifters and so on.The flat NGD characteristic which has a small fluctuation in a certain frequency range can improve the stability of phase and enlarge the application scope of NGD circuits.So it is very necessary to study the NGD and the flat NGD characteristics of circuits.Impedance transformers,power dividers,and couplers are fundamental microwave components in microwave communication systems and they can match impedance,divide or compose signals.They are widely utilized in various microwave circuits and systems.Therefore,the design and improvement of the existing passive components as well as combining NGD characteristics with microwave components to produce novel NGD components are also of high academic and practical significance.In this thesis,after researching lots of articles,a novel impedance transformer,power divider,and coupler with flat NGD characteristics are designed and proposed.The innovations of the thesis are as follows:1.In this thesis,a novel unidirectional DC-block impedance transformer with flatness and broadband NGD characteristics is proposed.Preliminary theoretical analysis method is given.Simulation and verification of the NGD impedance transformer are completed.2.A novel compact arbitrary terminated power divider with flat NGD characteristics is designed in the thesis.The detailed theoretical analysis and complete design process are given.Simulation and prototype verification of the NGD power divider are completed.3.In this thesis,a novel arbitrary terminated unequal positive and negative group delays coupler with wide and flat NGD bandwidth is improved and designed based on the circuit structures have been proposed.Detailed analysis and design process are given.Simulation and prototype verification of the coupler are completed.Simulation and prototype verification results show that the impedance transformer,power divider,and coupler proposed in this thesis can realize arbitrary port impedance.In addition,all three NGD components accomplish the purpose that has the flat NGD characteristics.