E.V. Ovchinnikova, S.G. Kondratieva

Navigation systems for new generation aircraft need antennas without worsening aerodynamic characteristics. Recent airborne antennas had the form of dipole and slot radiators. This paper considers possible ways to realize an array of microstrip radiators with omnidirectional pattern in azimuth. This array named RAA and placed on conical conducting surface, and the problem of RAA synthesis is solved in the paper for kR>> 100. Modeling of radiation pattern for microstrip radiator on conducting conical surface performed by both rigorous electrodynamics and numerical computation. The result of modeling is plotted in Fig.6. Synthesis of RAA construction is another problem requiring search of amplitude and phase distributions and element positions on aperture considering given number of patches in a ring. Possible solutions are illustrated in Fig.11. Excitation RAA patches with currents of equal amplitudes and different phases exhibits practically uniform radiation pattern within coverage area if element spacing are less than half-wavelength (Fig.15). Certain applications need array element spacing much bigger than half-wavelength. Corresponding radiation patterns are depicted in Fig.4. When element spacing d~33λ it is reasonable using parallel distribution system with in phase excitation and independent beamforming of separate beams. Thus, omnidirectional microstrip RAA with desired radiation pattern is synthesized. The possibility of obtaining almost uniform pattern throughout the scan sector by parallel excitation and independent beamforming of separate beams is shown. Specifications for design feeding system in digital beamforming are defined.