Vol.:(0123456789) 1 3 Journal of Computational Electronics https://doi.org/10.1007/s10825-019-01323-5 An optimum side‑lobe reduction method with weight perturbation Jafar Ramadhan Mohammed 1 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Generally, the phased antennas used in radar and communication systems have a certain taper to minimize the side-lobes. However, most tapering methods are inefcient for practical applications because they generally reduce the overall efciency of the system. It is therefore necessary to develop improved methods for reducing the side-lobes, especially for future ffth- generation (5G) communication systems, whose performance is expected to be drastically limited by interfering signals. Two new methods for obtaining low side-lobes with very little loss in directivity are presented herein. In both methods, the excitations of the elements in a uniformly excited array are perturbed such that the corresponding array factor constructs a specifc cancellation pattern. The cancellation pattern in the frst method is constructed using a simple analytical procedure, whereas in the second method it is constructed using a more powerful optimization algorithm. The cancellation patterns of both proposed arrays are then independently subtracted from the original, uniformly excited arrays to obtain new array pat- terns with deep side-lobe reduction. The simulation results show that the directivity diferences between the two proposed arrays and the uniformly excited array decrease as the number of array elements is increased; For example, when considering an array with 100 elements, the directivity diference is only 0.1435 dB. Moreover, the proposed arrays can reduce the peak side-lobe levels by more than 27 dB compared with the corresponding uniformly excited arrays. Keywords Antenna arrays · Radiation pattern synthesis · Side-lobe reduction 1 Introduction Current and future wireless communication systems, includ- ing 5G, require antenna arrays that can efectively decrease the interference level, which has been a hot issue among many researchers over the last few years and will continue into the future due to the crowded spectrum. Development of antenna arrays that can increase the throughput of such communication systems is required to meet the growing demands. These goals can be achieved by designing an array with specifc radiation pattern characteristics, i.e., high directivity and low side-lobes. The easiest design method, which also benefts from a simple feeding network, is to use a uniformly excited array; this approach ofers good directiv- ity but sufers from a high side-lobe level, which is undesir- able for the above-mentioned applications. Generally, low side-lobe levels can be achieved in phased array patterns by gradually reducing the element excitations from the center to edge elements of the array. Such antenna arrays are referred to as nonuniform amplitude distribution arrays [1]. Various analytical techniques, including windowing (or tapering) techniques, have been presented in literature for the synthe- sis of such array patterns with reduced side-lobes. However, most of these tapering methods are inefcient for practical applications, because they mainly sufer from the problem of large current taper ratio (CTR), i.e., wide variations between the amplitudes for the diferent elements of the array, espe- cially when the number of elements in the array is large. The resultant array thus sufers from low efciency, a complex feeding network, and high side-lobe levels. On the other hand, Chebyshev excited arrays are most commonly used in practice, because of their ability to pro- vide the narrowest beam width for a prespecifed side-lobe level. However, the directivity of this type of array is known to saturate when using a large number of array elements [2]. Thus, none of the above-mentioned synthesis techniques are suitable for arrays that consist of a very large number of elements. * Jafar Ramadhan Mohammed jafarram@yahoo.com 1 College of Electronics Engineering, Ninevah University, Mosul, Iraq