The paper considers design of the dual-band horn operating in significantly spaced frequencies. In W-band part of the system represents as a conical horn. In X-band part of the system represents as distributed aperture microwave feed system based on an improved waveguide tee is described in detail. In the proposed design of the waveguide tee at the junction point of the waveguides, a dual resonant iris is used as a mismatch compensator. This waveguide tee design has a small size, a wide working band and a large variability in matching of horn channels in antenna systems. Waveguide corners with a bend in a wide and narrow wall are also used in each channel to reduce overall dimensions of the radiation system. Two paired pyramidal horns forming a linear antenna array were used to obtain large directivity values and highly expressed directional properties. The numerical simulation of the system under study was carried out by the finite difference method in the time domain. The simulated results of the radiation system main characteristics are given.