Reducing the level of side lobes in the cluster microstrip antenna arrays of airborne weather radars for polar latitudes
Authors:   Saint Petersburg State University of Aerospace Instrumentation, Ryzhikov M.B. 
Published: December 2024

When solving the problem of on-board meteorological navigation for automatically controlled aircraft platforms or small aircraft both in the Arctic geo graphical zone and in the temperate zone, one of the key tasks in choosing a safe flight path is the requirement to bypass or fly over zones in which, based on the analysis of data obtained in the reflected signal, the presence of dangerous weather conditions for flight is established conditions: thunderstorms, intense precipitation in the form of snow or rain, turbulence or wind shear. As the results of research show, including for polar latitudes, by reducing the level of lateral radiation of antennas in the lower hemisphere, it is possible to reduce the probability of false detections of dangerous weather formations that occur after processing signals re-reflected from the underlying surface. This problem is especially relevant if the carrier performs a low-altitude flight on-board radar. If it is possible to implement the traditional amplitude distribution, it is possible to reduce the level of the side lobes to relatively small values (minus 28 dB or less), at which no false zones with dangerous weather conditions are observed on the on-board radar screen. However, as the results of the study show, in cluster antenna arrays with a single amplitude excitation of combined radiators, such side lobes arise, the maximum level of which is no longer regulated by the amplitude distribution. The ways of reducing these side lobes (including only in the lower hemi sphere) are investigated in this work. The mathematical apparatus of the theory of antennas and antenna arrays was actively used in the work, as well as numerical modeling using software based on a computer environment of matrix models, with integrated libraries for calculating the parameters of individual microstrip paths. By modeling, we investigate the levels of side lobes characteristic of cluster microstrip antenna arrays with different ways of combining emitters into groups, as well as explore ways to reduce it by implementing an upgraded amplitude-phase Dolph-Chebyshev distribution, leading to an asymmetric radiation pattern with a reduced radiation level in the lower hemisphere. The results of synthesis and modeling of the radiation characteristics of Ka-band antenna arrays with a reduced level of side radiation are presented, confirming the formation of an unstoppable side lobe, the cause of which is the clustering of the antenna array, performed in order to reduce the cost of the product by reducing the number of active controls of the amplitude-phase distribution of elements. The results of synthesis and modeling of the radiation characteristics of Ka-band antenna arrays with a reduced level of side radiation are presented, confirming the formation of an unstoppable side lobe, the cause of which is the clustering of the antenna array, performed in order to reduce the cost of the product by reducing the number of active controls of the amplitude-phase distribution of elements.