Improving side lobe level of X-band microstrip Rotman lens utilizing nonuniform distribution of output ports

Ehsan Zareian-Jahromi,Parvin Salehi,Raheleh Basiri,Hamidreza Karami

doi:10.3906/elk-1806-35

Abstract

A new microstrip Rotman lens with enhanced side lobe level (SLL) is proposed for X-band applications. A proper nonuniform distribution of the initial width of output ports is considered to improve the SLL. The benefit of SLL improvement is not based on using additional attenuators or amplifiers at the output ports. Moreover, an analytical background is presented to investigate the resulting SLL of the proposed structure. The advantage of SLL enhancement is obtained at all noncorner scan angles considering 10 GHz operating frequency. As the middle input port is excited, more than 3 dB of SLL enhancement is achieved at 10 GHz. The proposed structure provides even more accurate scan angles than those of the conventional Rotman lens. The designed structure is simulated using full-wave HFSS 15 software. The comparison between simulated results and measurements of the fabricated proposed Rotman lens shows good agreement.

Highlights

Beam steering antennas are encountered in numerous applications such as biomedical imaging, automotive anticollision radars, and communications [1,2,3]
A new microstrip Rotman lens with enhanced side lobe level (SLL) is presented, which is not based on using additional attenuators or amplifiers at the output ports
The benefit of SLL improvement is not based on using additional attenuators or amplifiers at the output ports

Summary

Introduction

Beam steering antennas are encountered in numerous applications such as biomedical imaging, automotive anticollision radars, and communications [1,2,3]. A beam-forming network (BFN) is a device producing desirable amplitude and phase distributions at its output ports. A new microstrip Rotman lens with enhanced SLL is presented, which is not based on using additional attenuators or amplifiers at the output ports. The benefit of SLL improvement is obtained for all steering directions except side values, ±22.5◦ , at 10 GHz. The effect of altering the initial width of output ports on the resulting scan angles is investigated. It is found that the proposed Rotman lens yields more accurate steering directions than the conventional Rotman lens at the central operating frequency. A new Rotman lens design including nonuniform distribution of output ports is presented, where the fabricated Rotman lens and corresponding measurements are detailed. It is shown that good agreement between measurements and simulation results is achieved

Conventional microstrip Rotman lens

Conclusion