Design of Rotman-lens feeding-circuit for multi-layer beam-scanning microstrip antenna in millimeter-wave band

Millimeter-wave technologies have been developed with increasing the need for efficient use of frequency resources. High gain and narrow beam antennas can be achieved in the millimeterwave band even by using physically small antennas. The same fractional bandwidth with lower frequency corresponds to much broader bandwidth channel in the millimeter-wave band. Beamscanning technologies are attractive to cover broad angular area with high gain of narrow-beam antennas [1]. Rotman lens is widely used in multibeam antennas for beam forming networks (BFN) which give required aperture distribution in arrays [2], [3]. Discrete beam-scanning can be fulfilled by switching the beams. However, the size of the feeding circuit using Rotman lens is large. Therefore, beam-scanning microstrip antenna in multi-layer configuration is in the development of this work. Rotman lens was developed at 76.5 GHz for the feeding circuit of the antenna. The simulated and measured performances are presented in this paper.