The transmission properties in two-dimensional plasma photonic crystal composed of plasma and yttrium–iron–garnet rods with square lattices are demonstrated under different electron densities and external magnetic fields. The TE and TM modes respond to the permittivity tensor and the permeability tensor produced by the magnetic field. For TM polarization, two distinct attenuation peaks appear in the ranges of 3.4–3.62 GHz and 3.78–4 GHz, induced by the external magnetic fields, and the location of these attenuation peaks can be modulated by modifying the electron densities. For TE polarization, a flat transmission spectrum was obtained in the range of 4–4.6 dB by increasing the electron density to $3\times {10}^{12}{ \mathrm{cm}}^{-3}$. Then, a Y-shaped plasma photonic crystal waveguide is designed. The transmission path can be modulated by changing the direction of the external magnetic field. By regulating the electron density, switching the Y-shaped waveguide on and off can be achieved.

This article solves the problem of determining the influence of an extended plasma jet on the radiation pattern of a short-grounded antenna in the frequency range of 1-3 GHz. The electron density and the electron collision frequency are set such that they correspond to atmospheric plasma jets of a barrier discharge in a helium flow. The problem of determining the radiation pattern is solved numerically using ANSYS HFSS and analytically using simple theoretical expressions for the field of a short antenna. The results using these two approaches are consistent with each other well. Based on the obtained results, a novel microwave diagnostic method for the atmospheric plasma jets was proposed.