Research On The Mechanism And Application Of End-fire Antenna Array

With the characteristics like low-profile beam coverage and low aerodynamic resistance, end-fire array antenna gradually attracts people’s attention in the applications of phased array. Airborne radar systems usually require both aerodynamic and wide beam coverage, both of which end-fire array can be a good balance between. But for a long time in people’s understanding, the end-fire array has middle gain, low aperture efficiency and strong coupling effects which are not suitable for phased array.Previous studies have demonstrated the use of high-gain plate end-fire antenna consisting of planar end-fire array can achieve considerable gain on the end-fire direction. This article will focus on the level on theory, and reveal deeper radiation mechanism of end-fire antennas and end-fire array, in order as a guide, to demonstrate the planar end-fire array’s capacity to achieve phased scanning and detecting functions. Specific research points following five areas:Firstly, study on the basic principles and characteristics of end-fire array. This part of study focus on this particular array form, ‘end-fire’, without regard to the form of array element. After summarizing of classical theory in academia in the past, some of the basic problems in array analysis and design are generalized in end-fire array.The second part is the analysis on the properties of coupling in arrays consisted by end-fire antenna. This part of the study bases on a series of coupling phenomena in the end-fire arrays consisted by end-fire antenna, simplify the complex antenna structure to a block model, and proved the end-fire coupling properties different with broadside array using a matrix analysis. These properties cause that the traditional coupling analysis and compensation methods are no longer applicable for end-fire array consisted by end-fire antenna.The third part of research presents two coupling estimation methods for end-fire array consisted by end-fire antenna. The purpose is to describe the coupling problems in this type array in a quantized way. Iterative estimation method and comprehensive test method are used to obtain a radiation field matrix from different approaches. This matrix has three constituent elements: the direct radiation field pattern, the coupling radiation field pattern and the coupling coefficient matrix. They represent a specific array’s coupling characteristics. According to this, the approximate compensation method based on coupling coefficient matrix is proposed.The fourth part research takes mounting environment into account, and choose plate end-fire antenna as array element. First, an improved estimation method of beam tilt angle is proposed, to achieve an accurate estimating for the influence of finite conductor planar ground to end-fire antenna’s performance. Then using the analysis method introduced in the third part, the performance of plate end-fire antenna in an end-fire array is evaluated. Analysis shows that different elements’ structures have significant difference in performance: some elements in array will produce a stable wide main beam which is beneficial for beam scanning, while some other elements in array will cause an unsmooth main beam which need to be compensation before use.The fifth part summarizes overall study results above, designs and fabricates a set of planar end-fire phased array. The array was tested twice when fed with a passive network and active T/R network respectively. Test results show that the array does not only keep a considerable gain and side-lobe suppression, but also achieve one-dimensional wide azimuth angle scanning, and the scanning accuracy meets the requirements.Following the steps of theoretical analysis, simulation analysis and experimental verification, the studies above accomplish extensive research on the radiation mechanism and application of end-fire array antenna.