A novel compact multilayer multibeam antenna array based on substrate integrated waveguide (SIW) is proposed in this letter for 5G millimeter wave (mm‐wave) applications. A multimode beam forming network (BFN) cascaded by phase compensation and coupling structures is folded to make the antenna array more compact. The phase difference between the output ports of traditional multimode beamforming network is very unstable, which would seriously affect the multibeam performance of antenna array. Therefore, the compensating phase shifter adopts the SIW transmission line structure with unequal length and width, which enables the multimode BFN achieving better performance in the bandwidth of 27–29 GHz. Four slot arrays are employed as the radiation structure. The overall structure of the proposed antenna consists of three parts, including a multimode beamforming network, a compensated phase shifter, and an SIW slot array. If these components are cascaded directly, the size of the antenna would be very large and the aperture efficiency will be low. So the proposed antenna is folded into three layers, one part for each layer. The overall antenna size is 66.7 mm × 47.5 mm (6.23λ × 4.44λ at 28 GHz). The antenna array is designed, fabricated, and measured. The measured results show that four deflected beams are realized in the band of 27–29 GHz. The radiation beams demonstrate a wide azimuthal coverage of ±48 deg, and a peak gain of 16.8 dBi for Port 1 excitation and 17.3 dBi for Port 2 excitation. The simulated radiation efficiency is better than –2 dB from 27 to 29 GHz. The proposed antenna features a compact size, low profile, good radiation performance, which is well suited for applications in the 5G mm‐wave communication systems.

中文翻译：

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适用于5G毫米波应用的紧凑型折叠式SIW多波束天线阵列

本文针对5G毫米波（mm-wave）应用提出了一种基于基板集成波导（SIW）的新型紧凑型多层多波束天线阵列。通过相位补偿和耦合结构级联的多模波束形成网络（BFN）可以折叠起来，以使天线阵列更紧凑。传统的多模波束形成网络的输出端口之间的相位差非常不稳定，这将严重影响天线阵列的多波束性能。因此，补偿移相器采用长度和宽度不相等的SIW传输线结构，这使得多模BFN在27-29 GHz的带宽中可以获得更好的性能。采用四个缝隙阵列作为辐射结构。拟议天线的整体结构包括三个部分，包括多模波束成形网络，补偿移相器和SIW缝隙阵列。如果直接将这些组件级联，则天线的尺寸将非常大，并且孔径效率将很低。因此，拟议中的天线被折叠成三层，每层一层。整体天线尺寸为66.7 mm×47.5 mm（28 GHz时为6.23λ×4.44λ）。天线阵列被设计，制造和测量。测量结果表明，在27–29 GHz频带中实现了四个偏转光束。辐射束显示出±48度的宽方位角覆盖范围，端口1激励的峰值增益为16.8 dBi，端口2激励的峰值增益为17.3 dBi。在27至29 GHz范围内，模拟辐射效率优于–2 dB。拟议中的天线具有尺寸紧凑，外形小巧，辐射性能好，