This study introduces a coplanar waveguide MIMO antenna design that offers both frequency and pattern reconfigurability. The antenna is intended for applications in WiMAX, WLAN, and X-Band. It is constructed using an FR4 substrate with dimensions of 1.6mm thickness and 0.025 loss tangent. Based on the proposed design, MIMO antennas can operate at 3.5 & 3.9GHz (WiMAX), 5.5 & 5.8GHz (WLAN) and 10.5 & 12.5GHz (X-Band). To accomplish this, two open-circuited 3mm x 3mm quatre wavelength transformers are linked to each radiator through PIN diodes. The performance enhancement of the reconfigurable MIMO antenna was fine-tuned utilizing microwave solvers in both CST and ADS. The system’s performance was validated through practical measurements. Furthermore, the analysis of diversity conducted on the suggested antenna reveals that the antenna has a low correlation coefficient (< 0.0001), channel capacity (< 0.4bits/sec/Hz), and total active reflection coefficient (< 0dB). The measured isolation of < -20dB is noticed for all three states. Antenna peak gain is 6.2dBi, with over 80% efficiency. A MIMO antenna with these characteristics suits a wide range of wireless communication systems.

The extended boundary condition method can be used to study plane-wave scattering by an ellipsoid composed of an orthorhombic dielectric–magnetic material whose relative permittivity dyadic is a scalar multiple of its relative permeability dyadic. The scattered and internal field phasors can be expanded in terms of appropriate vector spherical wavefunctions with unknown expansion coefficients, whereas the incident-field phasors can be similarly expanded but with known expansion coefficients. The scattered-field coefficients are related to the incident-field coefficients through a matrix. The scattering, absorption, and extinction efficiencies were calculated thereby in relation to the propagation direction and the polarization state of the incident plane wave, the constitutive-anisotropy parameters, and the nonsphericity parameters of the ellipsoid, when the eigenvectors of the real permittivity dyadic are aligned along the three semi-axes of the ellipsoid. As the electrical size of the ellipsoid increases, multiple lobes appear in the scattering pattern. The total scattering efficiency can be smaller than the absorption efficiency for some configurations of the incident plane wave but not necessarily for others. The nonsphericity of the object has a stronger influence on the total scattering efficiency than on the absorption efficiency. The forward-scattering efficiency increases monotonically with the electrical size for all configurations of the incident plane wave, and so does the backscattering efficiency for some configurations. For other configurations, the backscattering efficiency has an undulating behavior with increase in electrical size and is highly affected by the shape and the constitutive anisotropy of the ellipsoid. Even though the ellipsoid is not necessarily a body of revolution, it is anisotropic, and it is not impedance matched to free space, the backscattering efficiency can be minuscule but the forward-scattering efficiency is not. This feature can be useful for harvesting electromagnetic energy.

The simplest Lorentz-nonreciprocal medium has the constitutive relations ($\mathbf{D}={ϵ}_0\mathbf{E}-\mathbf{\Gamma }\times \mathbf{H}$ and $\mathbf{B}={\mu }_0\mathbf{H}+\mathbf{\Gamma }\times \mathbf{E}$). Scattering by a three-dimensional object composed of this medium was investigated using the extended boundary condition method. Scattering by this object in free space must be attributed to nonzero $\mathbf{\Gamma }=|\mathbf{\Gamma }|$. The differential scattering efficiency is immune to the transformation of the incident toroidal electric field phasor into a poloidal electric field phasor, or vice versa, and a consequence of this source invariance is the polarization-state invariance of the differential scattering efficiency when the irradiating field is a plane wave. Both the total scattering and forward-scattering efficiencies of an ellipsoid composed of the simplest Lorentz-nonreciprocal medium are maximum when the plane wave is incident in a direction coparallel (but not antiparallel) to $\mathbf{\Gamma }$, and the backscattering efficiency is minimum when $\mathbf{\Gamma }$ is parallel to the incidence direction. The total scattering and forward-scattering efficiencies are maximum when the incidence direction is parallel to the largest semi-axis of the ellipsoid if the incidence direction is coparallel (but not antiparallel) to $\mathbf{\Gamma }$. Lorentz nonreciprocity in an object is thus intimately connected to the shape of that object in affecting the scattered field.

The extended boundary condition method (EBCM) was formulated for the perturbation of a source electric potential by a 3D object composed of a homogeneous anisotropic dielectric medium whose relative permittivity dyadic is positive definite. The formulation required the application of Green’s second identity to the exterior region to deduce the electrostatic counterpart of the Ewald–Oseen extinction theorem. The electric potential inside the object was represented using a basis obtained by implementing an affine bijective transformation of space to the Gauss equation for the electric field. The EBCM yields a transition matrix that depends on the geometry and the composition of the 3D object, but not on the source potential.

As vector wavefunctions are available to represent incident and scattered fields in an isotropic dielectric-magnetic medium endowed with magnetoelectric gyrotropy, a transition matrix can be conceptualized to relate the scattered field coefficients to the incident field coefficients for scattering by an arbitrary scatterer composed of a linear medium. The elements of the transition matrix must satisfy certain conditions for zero backscattering. For a scatterer composed of a uniaxial dielectric-magnetic medium endowed with magnetoelectric gyrotropy, the extended boundary condition method can be formulated to determine the transition matrix. Numerical results obtained thereby lead to the formulation of a sufficient set of three zero-backscattering conditions: (i) The scatterer is a body of revolution with the incident plane wave propagating along the axis of revolution. (ii) The impedances of both mediums are identical. (iii) The magnetoelectric-gyrotropy vectors of both mediums are aligned along the axis of revolution, whether or not both magnetoelectric-gyrotropy vectors are co-parallel.