A Compact and Wideband Beam-Scanning Antenna Array Based on SICL Butler Matrix

A compact and wideband beamforming antenna array based on a substrate-integrated coaxial line (SICL) Butler matrix at 60 GHz is proposed in this paper. The cavity-backed patch antenna loading double-ridged horn antenna is designed to enhance a gain of 5.4 dB and a bandwidth of 2.7 GHz. Different phase centers of double-ridged horn elements are formed into a non-uniform array to reduce sidelobes by −7.9 dB. By introducing the defected ground structure (DGS) for a broadband coupler, a rotationally symmetric SICL Butler matrix is designed with a 55–70 GHz bandwidth and compact dimensions of 63 × 65 × 0.512 mm3. To validate the design, a prototype was fabricated and measured. The experimental results show a wideband −10 dB impedance bandwidth of 23.3% (55.4–70 GHz) with measured gains ranging from 15 to 16.1 dBi at 62 GHz. The one-dimensional beam scanning covers ±32°. The simulation and measurement results are in good agreement.