Electromagnetic fields in the near-zone of aperture antennas with round opening

Using the vectorized Kirchhoff integral, the external problem of electrodynamics is solved for emission of continuous aperture antennas with a circular shape radiating opening. The mathematical support was developed and calculations of amplitude and phase characteristics of electric and magnetic fields in the direction of the normal to the radiating opening and on plane surfaces parallel to the opening were carried out, the amplitude and phase distribution of the field sources being constant, the change in the opening diameter from half to 100 wavelengths. It is shown that the searchlight beam in the near-zone of such antennas is formed, diameters of the radiating opening being larger than 1.5–2 wavelengths, the amplitude of electric and magnetic fields oscillate uniformly over a larger range of values compared with cases of square and rectangular opening.