Abstract-A wideband half-mode substrate-integratedwaveguide cavity-backed slot antenna covering all Unlicensed National Information Infrastructure (U-NII) radio bands (5.15 GHz-5.85 GHz) is designed, fabricated and validated. By a half-mode implementation of a multi-moded cavity with nonresonant slot, a compact ultra-wideband antenna is obtained with very stable radiation characteristics, owing to the excellent antenna/platform isolation. Cork material is applied as antenna substrate, making the proposed antenna suitable for integration into floors or walls. In free-space conditions, an impedance bandwidth of 1.30 GHz (23.7 %), a radiation efficiency of 85 %, a front-to-back ratio of 15.0 dB and a maximum gain of 4.3 dBi at 5.50 GHz are measured. Performance is also validated when the antenna is deployed on various dielectric or conducting platforms and underneath different dielectric superstrates. Only the latter slightly detunes the antenna's impedance bandwidth. Yet, the complete frequency band of interest remains covered, owing to additional design margins incorporated in the requirements. Its compactness, unobtrusive integration potential and stable high performance in different environments make this antenna topology an ideal candidate for Internet of Things applications.

A cost-effective, compact and high-performance antenna element for beamforming applications in all 5G New Radio bands in the [24.25-29.5] GHz spectrum is proposed. The novel antenna topology adopts a square patch, an edge-plated air-filled cavity, and an hourglass-shaped aperture-coupled feed to achieve a very high efficiency over a wide frequency band in a compact footprint (0.48λ0 × 0.48λ0). Its compliance with standard PCB fabrication technology, without complex multi-layer PCB stack, ensures low-cost fabrication. The antenna feedplane offers a platform for compact integration of active electronic circuitry. Two different modular 1×4 antenna arrays were realized to demonstrate its suitability for broadband multi-antenna systems. Measurements of the fabricated antenna element and the antenna array prototypes revealed a -10-dB impedance bandwidth of 7.15 GHz (26.8%) and 8.2 GHz (30.83%), resp. The stand-alone antenna features a stable peak gain of 7.4 ± 0.6 dBi in the [24.25-29.5] GHz band and a measured total efficiency of at least 85%. The 1×4 array provides a peak gain of 10.1 ± 0.7 dBi and enables grating-lobe-free beamsteering from -50 • to 50 • .

Abstract-A novel remote antenna unit, intended for application in the downlink of an analog radio frequency over fiber system, is proposed, whose radiated power originates entirely from the optical signal supplied by a single multi-mode fiber. By operating the photodetector of the optical receiver at zero bias voltage, while omitting typical active components, such as transimpedance amplifiers, a fully passive unit, requiring no external power supply, is obtained. Instead, a careful co-design is performed to maximize the power transfer from photodetector to antenna within the frequency range of interest using an impedance matching network. A wideband cavity-backed slot antenna is implemented in air-filled substrate-integrated-waveguide technology. The antenna feed plane serves as integration platform for the optical receiver. The resulting downlink remote antenna unit is compact, cost-effective, energy-efficient and extremely reliable. Therefore, it is an ideal building block for novel, highly specialized, ultra-high density wireless communication systems, which require massive amounts of remote antenna units, deployed in attocells as small as 15 cm ×15 cm. A prototype operating in a wide frequency bandwidth ranging from 3.30 GHz to 3.70 GHz is constructed and validated. In free-space conditions, a broadside gain of −0.2 dBi, a front-to-back ratio of 8.8 dB and linear polarization with a cross-polarization level of −28.8 dB are measured at 3.50 GHz. Furthermore, a −3 dB gain bandwidth of 500 MHz is observed. Finally, the prototype is deployed in a unidirectional data link, achieving a symbol rate of 80 MBd over a distance of 20 cm.

No abstract