S. P. Skulkin, V. I. Turchin

We describe the method of calculation of a transient near field of the offset reflector antenna with dipole feed radiated delta - pulse. It is considered, that the effective frequency bandwidth is limited from above and from below, and the maximal wavelength is much less than sizes of the aperture, focal distance of a reflector and distance from a reflector to a observation point. Taking into account these assumptions the transient field can be written using space-time distribution of electrical current over antenna aperture. Using integration technique for delta-functions of complex argument, at each moment of time we can reduce the two-dimensional integral over a surface to one-dimensional integral over a line. Simple analytical expressions have been found for the transient near-fields of offset reflector antenna. The calculation method can be used for any reflector antenna with a round projection to an aperture plane, including symmetrical parabolic antennas. It is shown, that near-field responses of symmetrical and offset parabolic antennas consist of two impulses. The second impulse of the offset antennas usually has smaller amplitude, compare with symmetrical antennas.