Low sidelobes in array antennas of equal sub-arrays through element phase control

In the last few decades, many techniques have been proposed for the synthesis of large array antennas with simplified feed networks. In this framework of radar applications, the use of spatially contiguous sub-arrays of equal size allows the reduction of the number of antenna control elements, as well as to simplify the circuit complexity of the feed network. Despite the simplification of the antenna manufacturing and the costs saving, sub-arraying does not guarantee suitable radiation performances because of the usually limited control of the radiated pattern. As a matter of fact, unwanted high secondary lobes are generated in the far field pattern due to the periodic quantization of the element excitations. In order to improve the performance of the antenna, while maintaining an easy design of the array, various approaches have been presented. For instance, let us consider partially overlapped sub-arrays, the combination of tapered element excitations and sub-array excitations or sub-arrays of random sizes. More recently, a hybrid approach has been proposed for the joint optimization of both weights and dimensions of sub-arrays with unequal sizes.