Navegando por Assunto "Circuladores"

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Acesso aberto (Open Access)
Circuladores de grafeno de banda ultralarga para região THz
(Universidade Federal do Pará, 2019-06-07) SILVA, Samara Leandro Matos da; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
Non-reciprocal components are indispensable parts of many microwave and optical systems. In the future, THz communication systems will also require these components. Existing publications show that the bandwidth of graphene-based circulators in the THz region can be 10% to 20% with the use of rather complicated structures. The suggested circulators are formed by a graphene junction with concave pattern connected to the waveguides. Graphene is supported by SiO2/Si layers. The circulating behavior is based on the nonsymmetry of the graphene conductivity tensor that appears due to magnetization by a DC magnetic field normally applied to the plane of the graphene. We discuss the main parameters that define the bandwidth and its influence on it. Circulators have record bandwidth that is twice as high as those published. We have shown that the circulator Y can have the bandwidth of 42% in the frequency range (2.75 ÷ 4.2) THz, with the insulation better than −15 dB and the larger insertion losses that −2 dB, provided by the DC magnetic field polarization of 1.5 T and the chemical potential of 0.15 eV. For the two 4-port circulators we achieved a bandwidth of 44% for the same physical parameters.
Acesso aberto (Open Access)
Dispositivos não-recíprocos baseados em grafeno na região de THz
(Universidade Federal do Pará, 2019-02-28) CASTRO, Wagner Ormanes Palheta; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
Four new types of nonreciprocal graphene-based devices operating in the Terahertz region are suggested and theoretically analyzed in this work. They are two three-port circulators with Y and W geometries and two power dividers with different geometries. The cross section of the components has a three-layer structure, composed of graphene, silica and silicon. The planes of the figures of these components consist of a circular resonator of graphene and waveguides connected to it. The graphene resonator is magnetized normally of its plane by an external DC magnetic field, and the physical principle of operation of the devices is based on the dipole resonance of the magnetized graphene resonator. Using the Magnetic Group Theory, we analyze the scattering matrices of the symmetrical components of the devices. In addition, for the analysis of the circulators, the Analytical Temporal Coupled Mode Theory was also used. Numerical simulations were performed by a full wave computational program and the calculations demonstrate isolation levels better than -15 dB for both the circulators and the dividers. The Y-circulator has insertion losses around - 2.6 dB, bandwidth of 7.4% at the center frequency of 5.38 THz, whereas the circulator W showed insertion losses of - 2 dB, bandwidth of 4.5% at the center frequency of 7.5 THz. The DC bending magnetic field in the two cases was 0.45 T and 0.56 T, respectively. The power dividers have shown to posses the division of the signal between the two output ports of -4.4 dB with in the frequency band of 4.5% and 3.4% with magnetic filed of 0,8 T. The influence of geometric and physical parameters on the characteristics of the circulators is discussed. The frequency bands of the devices can be controlled dynamically by changing bias voltage applied between the graphene layer and the substrate.