Research of the Possibilities of Matching the Multi-element Receiving-Transmitting Irradiator Aperture
Currently, aperture antennas with spatial excitation, such as reflector antennas and phased array antennas, are widely used in radar. The composition of such an antenna includes an irradiator, which can be made in the form of a small-element array of radiators to form a set of necessary radiation patterns. Monopulse irradiators are often used, which form both total and difference directional patterns. When performing an irradiator based on waveguide parts, radiators in the form of horns or open ends of waveguides are installed in its aperture. Waveguide irradiators with four and twelve horns are widely used. One of the main electrical characteristics of such an irradiator when used as part of a receiving-transmitting antenna is the isolation of the transmitting and receiving paths. Matching the aperture of the transmitting and receiving irradiator has a significant effect on the isolation of its waveguide channels. With small transverse dimensions of the radiators in the form of open ends of waveguides, it is not possible to obtain high isolation of waveguide channels without the use of additional matching elements. The task of research the effect of matching the aperture of a waveguide multi-element irradiator on the isolation of its transmitting and receiving channels, as well as the ways of matching its radiators, is set.The article considers a four-horn irradiator, the aperture of which contains radiators in the form of open ends of a square waveguide. Each radiator has the radius rounding required for the manufacture of the product using the available technological processes. To match the emitter, a dielectric plate is installed inside it. During the research the thickness of the plate and its location relative to the aperture plane changed. The characteristics of matching the radiators with a plate made of teflon, polyethylene and ST-4 material based on polymers filled with titanium dioxide are presented.The proposed method of matching the opening of a multi-element irradiator with a transverse emitter size of 0,68λ (λ is the wavelength in free space corresponding to the average frequency of the operating band) makes it possible to improve the isolation of the receiving and transmitting waveguide channels by at least 4 dB in the frequency band of up to 3%.