Study Of Anomalous Propagation Velocity Of Frequency Signal

It is a cross-issue involving many subjects simultaneously for us to study theanomalous propagation velocity of frequency signal,and,as a young and spunky field,ithas theoretical and practical interest.However,as for this field, its development in theoryis behind that in experiment and is far from maturity.In this field, some experimentalresults, which contradict our traditional theories,have not been obtained a satisfactoryinterpretation theoretically.What is more, to our surprise, this anomalous propagation ofelectromagnetic wave can also take place in free space. Anomalous propagation velocityof frequency signal include slow light velocity,ultra-slow light velocity, superluminalgroup velocity and negative group velocity,et.al in electricity or light field. In this paper,we make frequency signal propagate in the mismatched transmission linegroups(coaxial photonic crystal),used transmission delay, researched some anomalouscharacteristic of frequency signal superluminal group velocity comprehensively andseriously, the characteristic of signal transmission speed in the condition ofsuperluminal group velocity is discussed. When an amplitude modulated sinusoid signalis sent into a mismatched transmission line groups at some special carrier frequencies itsgroup velocity of envelope is transmitted at superluminal speed. The speed fluctuatingaccording to the change in the length in the line is tested. The propagation groupvelocity of the signal envelope in the forbidden band is faster than the speed of light (c)in vacuum, even negative group velocity occurs when the total length of themismatched line group is long enough, and so on. According to the experiment, there isdifference in not only the speed value but also the speed undulate between superluminalgroup velocity in certain condition and the light speed in general propagation. Theexperimental result reveals that the obvious contrast between the characteristic ofsuperluminal group velocity propagation speed and that of electricity or light in normalpropagation exists.