Studying On Electromagnetic Transparency And Dispersion Compensation

The control and compensation of metamaterials dispersion are hot topics in electromagnetism.Based on the dispersion controlling theorem,this dissertation focuses on transparent metamaterials in THz waveband and compensating envelope distortion in microwave waveband.Transparent metamaterials are firstly investigated,especially for omnidirectional transparent metamaterials and ultra-wideband transparent metamaterials.Based on the impedance matching theorem and the surface equivalence theorem,omnidirectional transparent metamaterials are proposed,whose effectiveness are demonstrated by simulation and experiments.Ultra-wideband transparent metamaterials are further proposed,whose transparent bandwidth are over 10 percentage in normal incidence.Secondly,compensating group delay distortion of signals based on engineered material dispersion is investigated.By introducing wideband anomalous dispersion in metamaterials,the negative group velocity is achieved.By using the negative group velocity to obtain the leading group delay,the lagging group delay in transmission system is eliminated and the envelope distortion of signals is compensated.Finally,compensating envelope distortion based on non-Foster elements is investigated.By proposing a two-port non-Foster element,wideband anomalous dispersion is achieved.By using anomalous dispersion to eliminate normal dispersion in Foster elements,the dispersion response of the total reactance and immittance in circuits is independent with frequency.That means no dispersion in transmission system.