Measuring the Elevation Angle of an Airborne Object by Phase Direction Finding in a Multi-Ring Antenna Array

Abstract

Introduction. Radar stations for surveillance of airborne objects operating in the shortwave range are characterized by a number of limited technical characteristics, one of which is the azimuth viewing sector. The use of a linear antenna array (AR) as a receiving array provides the viewing angle of only up to 60°. When modernizing the station, this limitation was removed by applying an AR with a ring structure (currently a multi-ring AR is used). In practice, after performing a number of spatial processing algorithms, the operator obtains the azimuth, range, and speed of the observed object. However, due to the peculiarities of shortwave signal propagation, the accuracy of measuring these parameters does not ensure stable tracking of airborne objects. The use of multi-ring ARs also allows the elevation angle to be measured with a subsequent calculation of the height of the object.Aim. Analysis of the phase distribution of the incident wave at the aperture of a multi-ring AR, as well as spatial processing of the received signal using the phase direction finding method to improve the accuracy of elevation angle measurements.Materials and methods. Computer simulation in the MATLAB environment was carried out to form phase distributions on the elements of a multi-ring array, to calculate the elevation angle using the phase method, and to form portraits of the surveyed object. This environment has been successfully used to solve a wide range of problems of varying complexity in both industry and research fields.Results. The possibility of using the phase method of direction finding of a radiation source to improve the accuracy of elevation angle measurement is demonstrated based on the conducted computer simulation. The obtained results were verified on the example of surveying an airborne object by a shortwave radar station.Conclusion. The results obtained proved the relevance of using the phase method when performing spatial signal processing by a shortwave radar station. The proposed method made it possible to eliminate the ambiguity in measuring the elevation angle and to increase the accuracy of its determination, which is a new result in relation to the systems under consideration.

Keywords

• shortwave station
• radiation source
• wave front
• ionospheric propagation
• elevation angle determination
• phase method
• base