Butler Matrix Components Based on Substrate Integrated Waveguide Fed by Microstrip Separation Feedline for 5G Application

This paper presents a beamforming component based on vias variation substrate integrated waveguide (SIW) method at Ka-band. At Ka-band, the losses are high when planar structures are implemented due to the small wavelength, beside the expected losses from the component’s losses. Therefore, SIW technology with vias manipulation is introduced. This work aims to present a low loss coupler, crossover, and phase shifter for beamforming based on SIW at 26 GHz. Coupler and crossover are designed with vias variation based on the metallic fill inside the vias microstrip separation feedline, used for input and output ports to achieve enough distance between each adjacent port, and compact design with loss phase error. The proposed designs are simulated using CST software and fabricated using Rogers 5880 substrate with thickness of 0.508 mm and permittivity of 2.2. The measured performance agreed well with the simulated results. A return loss of less than −20 dB is achieved over a bandwidth of 5 GHz. A perfect −3 dB and 0 dB are obtained at coupler and crossover outputs. The measured phase difference −88.8∘ is observed at the outputs. Overall, the coupler and crossover show great potential performance for Ka-band applications.