A bidirectional multi-beam transmit-reflect-array (TRA) antenna has been proposed for the space-air-ground-sea integrated network (SAGSIN). The TRA consists of alternating transmission and reflection elements, and its aperture phase distribution comprises focusing and periodic phases. The combination of different transmission and reflection apertures with varying periodic phase differences can achieve TRA with different numbers of transmitted and reflected beams. Total transmission and reflection elements with linearly varying phases with thickness are used to analyze the relationship between the gains of transmitted and reflected beams. It has been proved that the gain ratio of the transmitted and reflected beams can be adjusted by changing the area ratio of the transmission and reflection aperture. To verify universality, a single-layer TRA has been designed for verification, and the simulation and measurement results are in good agreement. The measurement results have demonstrated that the proposed TRA antenna can realize the tri-beam transmission and dual-beam reflection.

This paper presents a 1×4 cavity-backed endfire dipole antenna array based on substrate-integrated suspended line (SISL) platform. A double-side substrate-integrated suspended line (DSISL) self-packaged feeding network with irregular boundaries is designed for the array. By utilizing the DSISL feeding network, the radiation loss and substrate loss of the feed line are effectively decreased thus efficiency of better than 91% is achieved. Instead of the conventional metallic cavity, the proposed cavity structure is realized by multiple substrate layers. A predominantly TE 10 aperture field is obtained by adjusting the sizes of the backing cavity. Measured results show that the proposed dipole antenna array has narrow beam widths in the E-plane and obtained 10-dB impedance bandwidth of 19.7%, i.e., from 22.77 to 27.75 GHz which can cover the 24 GHz automotive radar band (24.25-26.65 GHz). Moreover, front-to-back ratio of better than 26 dB, high gain of better than 14.1 dBi and low side lobe level of better than -15 dB are achieved over the automotive radar frequency band.

A dual-band multimode high-gain stacked-patch antenna based on substrate integrated suspended line (SISL) is proposed for 5G applications. The proposed antenna comprises five low-cost FR4 dielectric substrate layers and ten metal layers with embedded air cavities. The driven patch generates TM ₁₀ mode and TM ₀₂ mode, and the other two modes are generated by etching the U-slot and horizontal slot on the driven patch to achieve dual-band. The stacked patch with the U-slot can suppress the radiation pattern split of TM ₀₂ mode, improve the antenna gain in the high-frequency band, and generate radiation null to increase the out-of-band gain-suppression level. To verify this principle, the antenna is fabricated and measured. The measured results show good agreement with the simulated ones and the proposed antenna operates at 3.21–3.66 and 4.75–5.40 GHz, which can cover the 5G communication band. The antenna has high efficiency. The maximum gains in the two bands are 9.12 and 8.65 dBi, respectively.

This letter presents a wide band high-gain filtering antenna for fifth-generation (5G) applications based on substrate integrated suspended line platform. The filtering antenna mainly consists of a driven patch, a stacked patch, and a rectangular loop. By adding a rectangular loop to the conventional patch antenna, an additional resonance can be excited. Meanwhile, the frequency selectivity of the lower band is obtained due to the formation of a radiation null. Then, a patch is stacked on the driven patch, which also generates an extra resonance mode and a radiation null at the upper band edge. Therefore, a bandpass filtering function is realized and the bandwidth is greatly improved with three resonance frequency points. The fractional bandwidth is from 4.28 to 5.34 GHz (22.04%), covering the specific 5G n79-band (4.4–5.0 GHz). Moreover, the height of the antenna is only 0.08 λ ₀ ( λ ₀ is the wavelength in free space of the central operating frequency), and the peak gain of the antenna is 10.4 dBi. It is worth mentioning that the whole design is low-cost since it is based on full FR4 substrates.

novel stacked patch antenna based on substrate integrated suspended line (SISL) technology is proposed. The antenna is designed to be self-packaged using five substrate layers with embedded air cavities. Via is utilized to connect the antenna driven patch with the feed line and then resonant frequency at 5.2GHz is generated. U-shape slot is etched on the antenna driven patch for impedance matching. In order to further extend the impedance bandwidth, a stacked patch with slant slot is introduced and then another resonant frequency at 6.2 GHz is produced. According to the measured results, the antenna element achieves a fractional bandwidth of 17.5% from 5.2 to 6.2 GHz and gain of 9.7 dBi. Based on the antenna element, the 8-element antenna array with feeding network is presented. The microstrip-slotline balun is introduced in the feeding network to achieve 180° phase difference with equal amplitude so that symmetrical radiation patterns are achieved. Simulation and measurement results for the proposed antenna array are in good agreement. In the frequency band from 5.28 to 6.05 GHz, antenna gain of 16.24 dBi with gain flatness variation of 1.5 dB is achieved. Additionally, the front-to-back ratio of the self-packaged antenna array is better than 20 dB.

A substrate integrated suspended line (SISL) circularly polarized stacked patch antenna and array is proposed. The stacked patch is introduced to achieve impedance matching and circular polarization. A windmill slot is etched on the driven patch to generate resonant frequencies of 5.05 and 5.3 GHz. Another resonant frequency of 6.5 GHz also exists due to the slot and driven patch. The proposed antenna is based on five dielectric layers, among which two layers are hollowed. On the basis of the measured results of the antenna element, the fractional impedance bandwidth of 28.3% from 4.8 to 6.38 GHz and 3 dB axial ratio (AR) bandwidth from 5.29 to 6.02 GHz are obtained. In addition, the antenna gain is larger than 8 dBic. A sequential rotation feeding network with 90° phase difference between each output port is presented to feed the antenna array with four elements. For the proposed antenna array, the measured results agree well with the simulated results. In the impedance bandwidth from 5.03 to 6.16 GHz and 3 dB AR bandwidth from 5.13 to 6.2 GHz, the antenna peak gain ranges from 12 to 13.8 dBic.