Scan Blindness Effect for Free Electron Beam Fed Infrared Diffraction Radiation Antenna Grating

The effect of scan blindness is known in the large phased array antennas. It is caused by the excitation of the ultrahigh-Q lattice modes of array as a periodic open resonator. We consider, in full-wave manner, the electron beam diffraction radiation in the presence of finite grating made of many graphene-coated circular dielectric nanowires. We assume a constant velocity for the modulated in density electron beam and take its field as the incident one. To characterize the graphene, we employ quantum-theory Kubo formalism and resistive sheet boundary conditions. Then, the electromagnetic boundary value problem of wave scattering is cast to a Fredholm second-kind matrix equation for the current azimuth harmonics in local coordinates, using the separation of variables and the cylindrical functions addition theorem. This method has a guaranteed convergence and enables precise control over numerical accuracy. The numerical results are presented for the gratings with hundreds of wires and focus on the plasmon and lattice-mode resonances. Potential applications of the investigated effect are also described.