Low loss waveguide-based Butler matrix with iris coupling control method for millimeterwave applications

• Main Authors: W. Almeshehe, Muataz, Murad, Noor Asniza, A. Rahim, Mohamad Kamal, Ayop, Osman, Zubir, Farid, A. Abd. Aziz, Mohamad Zoinol, N. Osman, Mohamed, Majid, H. A.
• Format: Article
• Language: English
• Published: Taylor&francis 2023
• Subjects: TK7800-8360 Electronics
• Online Access: http://eprints.uthm.edu.my/11648/1/J16159_e7002cba332d9d3a6e4edac8cb3c90d9.pdf; http://eprints.uthm.edu.my/11648/; https://doi.org/10.1080/17455030.2021.1880032
• Institution: Universiti Tun Hussein Onn Malaysia

This paper proposes a low loss 4 × 4 Butler matrix based on rectangular waveguide cavity resonators technology for millimeterwave beamforming network using iris coupling method. This method has the advantage of controlling the electricalfields and the couplingfactor inside a complex medium such as waveguide cavity resonators. The coupling factor of 6 dB for 4 × 4 Butler matrix is achieved by tuning the iris coupling k-value between the waveguide cavity resonators. Thus, avoiding a higher phase difference losses and component losses at upper millimeterwave bands. To validate the proposed method, CST software simulations are performed under several iris coupling k-values to achieve a 6 dB coupling factor. Then, the proposed 4 × 4 Butler matrix is 3D metal printed using selective laser melting (SLM) technique. The measured reflection and isolation coefficients are observed below −10 dB, with coupling coefficients ranging between −6 and −7 dB. The phase differences of −42.02°, 42.02°, −130.95°, and 133.3° are achieved at the outputs. It confirmed that using this proposed method has the superiority over the conventional microstrip and waveguide coupling methods by a 1 dB coupling factor loss and a 3° phase difference error.