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A new structure for isolator is proposed in this work. The proposed structure consists of metamaterial-magnetoplasma semiconductors parallel plate structure. The utility of magnetoplasma semiconductors is promising in developing nonreciprocal components in the submillimeter-wave and millimeter-wave bands for satellite communications. Metamaterials (MTMs) is used to enhance the behavior of the isolator.

Isolators are needed in advanced satellite communications application in submillimeter wave energy bands with wavelength ranges between 1000 - 100 μm (300 GHz - 3 THz). Isolators use the TM_{o} mode only, the effective refractive index of which is different for forward and backward propagation, if the magnetization is properly adjusted [

The geometry of the proposed configuration is displayed schematically in

The semiconductor is considered to be GaAs. The Drude-Zener model is applied to describe the interaction between the magnetically biased semiconductor and the field. In this work, the plasma or the ionic medium is characterized by the scalar permeability μ_{0} and the fol-

lowing relative permittivity tensor [

where

, , ɛ_{r} is the relative permittivity, ω is the angular frequency, ω_{p} is the electron plasma frequency, ω_{c} is the cyclotron frequency, ν_{c} is the collision frequency, N_{e} is the density of nearly free electrons in the semiconductor, m_{e}^{*} is the effective electron mass, μ_{e} is the electron mobility and B_{ }is the applied magnetic flux density. In the Drude-Zener model the cyclotron frequency must be greater than the collision frequency. In the lossless case, ν_{c} = 0 the tensor entries reduces to

Equations (2) and (3) show that there is a singularity at ω = ω_{c}. The Gyroelectric ratio, ε_{3}/ε_{2}, is defined as follows

Metamaterials (MTMs) has both negative permittivity ε_{m} and negative permeability µ_{m}. Both ε_{m} and µ_{m} are function of frequency as follows [

In this work, we consider both ε_{m }and µ_{m} linear and lossless. The values of the parameters ω_{r}, ω_{p}, and F are chosen such that ε_{m} < 0 and µ_{m} <0.

In this study we only considered transverse magnetic fields (TM). The TM fields are assumed to have the following forms:

where γ = α + jβ is the complex propagation constant. Applying Equations (7) and (8) into Maxwell’s equations we get the field equation for each medium. We can get the dispersion Equation (9) by applying the boundary conditions at y = 0, i.e. E_{z} and H_{x} must be continuous.

where, k_{0} is the wave number is free space, , b is the total thickness of the waveguide, h is the thickness of the semiconductor layer as indicated in

In Equation (9), squaring γ gives linear term of the propagation constant β and second order term of β. The linear term of β made it possible to have an isolator from the proposed configuration.

Equation (5) is numerically plotted in

shows the permittivity ε_{m} of MTMs as function of frequency (ω). We notice that ε_{m }is negative for ω < ω_{p} = 150 π = 471.2 GHz. The permeability µ_{m} of MTMs, Equation (6) is plotted as function of frequency (ω) in _{m} is negative for

The real and imaginary parts of the effective permittivity as function of frequency are shown in

the calculation we choose the value of collision frequency, the value of cyclotron frequency. The values are chosen such that the Drude-Zener condition is satisfied. That is ω_{c} > ν_{c}.

The dispersion Equation (9) is solved numerically. The forward and backward wave propagation is plotted as function of frequency as exhibited in

It can be seen from

We proposed a two layer system for an isolator. The proposed structure consists of semiconductor substrate and MTMs cover. The proposed structure exhibits a nonreciprocal device at the vicinity of EWR. The maximum phase difference occurs at 257 GHz.