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

Abstract

A new microstrip Rotman lens with enhanced side lobe level (SLL) is proposed for X-band applications. Aproper nonuniform distribution of the initial width of output ports is considered to improve the SLL. The benefit of SLLimprovement is not based on using additional attenuators or amplifiers at the output ports. Moreover, an analyticalbackground is presented to investigate the resulting SLL of the proposed structure. The advantage of SLL enhancementis 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 accuratescan angles than those of the conventional Rotman lens. The designed structure is simulated using full-wave HFSS 15software. The comparison between simulated results and measurements of the fabricated proposed Rotman lens showsgood agreement.