A Compact High-gain Rotman Lens Multibeam Antenna with Low Crossover Level and Sidelobe

A Rotman lens based high-gain multi-beam antenna is proposed with low crossover level and sidelobe. The antenna is composed of a substrate integrated waveguide (SIW) Rotman lens, an SIW slot array, and several coupling slots. The SIW slot array is stacked on the top of the Rotman lens, and the coupling slots can transmit the field from the bottom Rotman lens beamforming network (BFN) to the top radiator array, thus achieving a compact antenna structure. By switching the feeding among the different input ports of the Rotman lens, the signals from the output ports can achieve a different phase gradient, and thus scan the beam radiation direction. In addition, to improve the performance on the crossover level and sidelobe, a novel feeding method, i.e., dual source excitation, is used in the antenna design, which can increase the source aperture size and beam number simultaneously. The large aperture size of the source will result in a tapered output magnitude distribution. Hence, the sidelobe level (SLL) can be suppressed significantly. To verify the feasibility of the multi-beam antenna design, a prototype is simulated at the center frequency of 5.8GHz. The simulated results show that the proposed antenna can achieve the beam scanning range of ±55° with the gain variation of 21.6dBi to 23.6dBi. The crossover level and the SLL are better than -2.2dB and -15.0dB. In our opinion, the compact antenna structure and the good passive beam scanning characteristics make the antenna a suitable choice for low-cost communication and sensing applications.