Wideband Beam-Forming Networks Utilizing Planar Hybrid Couplers and Phase Shifters

In this article, a new approach to designing 6 x 6 beamforming networks (BFNs) for producing five or six beams is presented. The configuration of the 6 x 6 BFNs is designed utilizing planar wideband hybrid couplers and phase shifters. A new type of wideband hybrid coupler is built based on a slotline resonator and microstrip-to-slotline transitions. The proposed coupler design can achieve high level of isolation between the sum and difference ports. Two different formats of wideband 6 x 6 BFNs are then developed, to generate five and six beams, respectively. A prototype is fabricated and tested, and the experimental results agree with the simulation ones very well, achieving a wide operating bandwidth of more than 30%. Finally, the BFN is verified by feeding a six-element array, and the realized patterns match the predicted ones very well, demonstrating the function of the BFN. The topology of an extended 12 x 12 BFN is also given to demonstrate the possibility of creating higher-order BFNs using the presented approach.