Homegenization And Non-Foster Dispersion Compensation Of Artificial Microwave Medium

Metamaterials consist of artificially constructed subwavelength resonant cells which can move the Drude-Lorentz dispersion originally observed at ultrahigh frequencies due to atom-scale resonances to the optical and microwave regions.At present,the application of artificial media is mainly confronted with three challenges.First,the normalized periodicity of the unit cells in existing metamaterials ranges between 1/6 and 1/10 of wavelength.The minimum size of a bulk metamaterial that is able to exhibit the desired effective characteristics is already large which may not be applicable in some cases obviously.Second,the fantastic property of metamaterials is derived from the strong dispersion characteristic of electromagnetic resonance.Base on K-K principle,strong dispersion corresponds to a narrow frequency band which results in a narrowband for metamaterials.So we need to compensate the dispersion for some broadband applications.Third,the strong dispersion of metamaterials is inevitably accompanied with a large loss which means that most of the energy will be consumed in the transmission.Therefore,in practical applications,we need to reduce the loss by introducing active circuit or use the substrate with low loss tangent.In order to solve the problem of insufficient homogeneity of metamaterials,this paper proposes a method for constructing deeply-subwavelength electromagnetic resonance cell based on half-wavelength transmission line resonator using monolayer planar process.In the experimental verification,we design and implement a bulk left-handed metamaterial.With the periodicity of the unit cells ranging from 1/61 to 1/48 of wavelength,the negative refractive index can be clearly measured in the frequency range between 1.02 and 1.3 GHz.Simulations further show that by employing the semiconductor manufacturing technology,this homogeneity can be further reduced to a level of 1/300 of the wavelength at similar gigahertz frequencies.On the other hand,in order to compensate the strong dispersion inherent in metamaterials,an integrated negative impedance conversion(NIC)circuit based on Linwill open-loop stable structure is proposed in this paper.The simulation results show that the NIC circuit can realize negative inductor with Non-Foster property in a wide frequency band.