A Compact Multi-Beam End-Fire Circularly Polarized Septum Antenna Array for Millimeter-Wave Applications

• Published in: IEEE access Vol. 6; pp. 62784 - 62792
• Main Authors: Cheng, Xiaohe, Yao, Yuan, Tomura, Takashi, Hirokawa, Jiro, Yu, Tao, Yu, Junsheng, Chen, Xiaodong
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna arrays; Antenna gain; Antenna measurements; Antenna radiation patterns; Antennas; Bandwidths; Butler matrices; Butler matrix; Circular polarization; circularly polarized; end-fire; Matrices (mathematics); millimeter wave; Millimeter waves; multi-beam; Phase shifters; Septum; substrate integrated waveguide; Substrates; Waveguides
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2018.2876872

In this paper, a novel circularly polarized end-fire septum antenna based on substrate-integrated-waveguide (SIW) is proposed in the 60-GHz band. By introducing four symmetrical tapered curved air slots in three stacked open-ended SIW layers, the antenna can obtain an operating bandwidth from 57.2 to 63.4 GHz for both AR < 3 dB and <inline-formula> <tex-math notation="LaTeX">\vert S_{11}\vert < -21 </tex-math></inline-formula> dB. Besides, the half-power-beam-width and 3-dB axial-ratio (AR) beam-width are all wider than 79°, and a stable gain of 7.57 dBic with a variation of 0.15 dBic can be achieved in the working band. A <inline-formula> <tex-math notation="LaTeX">4 \times 4 </tex-math></inline-formula> SIW Butler matrix based on SIW with three same substrates is then designed. The modified two-layer phase shifters realized by the different path distance are employed in the folded Butler matrix. By combining the antenna element and the Butler matrix together, a four-beam antenna array with circular polarization wave is realized. The proposed array has been fabricated and measured. The measurement results show that the antenna gain up to 11.01 dBic, −10 dB impedance and isolation bandwidth from 57.8 to 62.5 GHz (except at around 58.3 GHz), stable radiation pattern and a wide angular range of ±37° can be obtained. The measured AR values of the main lobe range of four beams are all less than 5 dB from 58 to 60 GHz.