Olivier Caytan

A compact and versatile transition from grounded co-planar waveguide to air-filled substrate-integrated waveguide (AFSIW) is presented, enabling broadband, low-loss interconnection of surface-mount RFICs to high-performance, cost-effective printed-circuit-board (PCB)-based AFSIW systems. The transition achieves broadband operation (up to 63%fractional bandwidth) within a minimal footprint (below 0.57 λ₁ × 0.31 λ₁) by leveraging a resonant rectangular aperture in combination with a microstrip and air-filled substrate-integrated waveguide (AFSIW) stub. Interfacing with AFSIW waveguides of varying height is enabled through the use of a stepped-impedance transformer. In addition, a novel stencil-based assembly process is proposed to ensure void-free stacking of immersion-silver (iAg)-finished PCBs, thereby minimizing insertion loss. First, a low-profile prototype for dense in-array IC integration is manufactured, achieving an average insertion loss (IL) below 0.58 dB across a 63.2% bandwidth spanning [20.8–40] GHz, while maintaining a compact footprint of 0.52 λ₁×0.16 λ₁, with λ₁ = 20.8 GHz. To further reduce AFSIW transmission loss from 0.1 to 0.04 dB/cm, a second design tailored for interfacing with increased-height AFSIWs is realized by employing a stepped-impedance transformer without requiring depth-routing. This multi-layer transition achieves 27.3% bandwidth over [22.8–30] GHz with an average insertion loss of 0.64 dB. These results confirm the proposed transition and assembly method as a reliable, broadband, low-loss, and scalable solution for next-generation AFSIW-based active antenna arrays.

In this column article, millimeter-wave (mmWave)-over-fiber-based distributed antenna systems (DASs) are showcased to realize reliable high-data-rate wireless links for demanding applications, such as interactive virtual reality, where line-of-sight blockage due to the presence of the user’s own body and external (human) blockers frequently occurs. Distributed architectures, such as DASs, pose a good solution to alleviate these losses, while keeping the background exposure low. Additionally, [air-filled (AF)] substrate-integrated waveguide (SIW) antenna topologies are compared to dipole and patch antennas and are found to be more robust in close proximity to the body, in terms of both bioelectromagnetic (bio-EM) effects and communication performance. Finally, a practical demonstration of a mmWave DAS with head-mounted user equipment (UE) exhibits reliable 12-Gb/s wireless links in the n257 band under full rotation and head tilting of the user. By leveraging distributed multiple-input, multiple-output (DMIMO) techniques, the throughput can even be raised to 24 Gb/s.

Due to their large bandwidth, relatively low cost, and robust performance, uwb radio chips can be used for a wide variety of applications, including localization, communication, and radar. This article offers an exhaustive survey of recent progress in uwb radar technology. The goal of this survey is to provide a comprehensive view of the technical fundamentals and emerging trends in uwb radar. Our analysis is categorized into multiple parts. Firstly, we explore the fundamental concepts of uwb radar technology from a technology and standardization point of view. Secondly, we examine the most relevant UWB applications and use cases, such as device-free localization, activity recognition, presence detection, and vital sign monitoring, discussing each time the bandwidth requirements, processing techniques, algorithms, latest developments, relevant example papers, and trends. Next, we steer readers toward relevant datasets and available radio chipsets. Finally, we discuss ongoing challenges and potential future research avenues. As such, this overview paper is designed to be a cornerstone reference for researchers charting the course of uwb radar technology over the last decade.

A substrate integrated coaxial line (SICL) technology implemented in standard printed circuit board (PCB) technology is proposed to realize shielded miniaturized millimeterwave (mmWave) components, eliminating spurious feed network radiation that may influence the antenna array’s radiation pattern. Additionally, coupling to neighboring signal lines is avoided by the self-packaging characteristic of SICL lines, thereby minimizing undesired crosstalk in the routing network. A thorough comparison to more traditional transmission lines, such as grounded co-planar waveguides (GCPWs), shows excellent packaging behavior by minimizing radiation and increasing the routing flexibility between the compact functional components. Further validation of this technology is done by implementing several essential components for beamforming networks: a coaxial via transition, a packaged hybrid coupler and an improved, miniaturized hybrid coupler with direct interfacing. The proposed shielded coaxial via transition from SICL to SICL exhibits a measured insertion loss smaller than 0.74 dB in a broad operational frequency range from 23.75 GHz to 32.5 GHz (31%), covering the n257, n258 and n261 5G bands. In this frequency range, the (miniaturized) SICL hybrid coupler has a measured amplitude imbalance below 1 dB (0.8 dB) and the phase imbalance does not exceed 6° (3°). The proposed miniaturized SICL hybrid coupler has a footprint of only 4 mm in diameter.

In this contribution, we investigate the implementation of air-filled substrate-integrated-waveguide (AFSIW) components based on the assembly of multiple standard manufactured single printed circuit boards (PCBs) as a cost-effective, low loss routing alternative for millimeterwave antenna arrays. To this end, a transition from grounded co-planar waveguide (GCPW) to AFSIW is designed, fabricated and measured for integration purposes with active electronics in the n257 5G band. The measured minimal insertion loss equals 0.7 dB around 27 GHz. To further validate our approach, a compact, fully shielded AFSIW filter, including the aforementioned transition, is designed and prototyped. It is shown that the component radiates less than 5% of its power, eliminating most of the spurious radiation from feed networks.

Urban freight distribution via inland waterways is an important way to boost the quality of life in major urban areas with dense water networks. Cost-effective autonomous pallet shuttle barges (PSBs) are key to accelerate the shift from road-based transport to inland waterways. Yet, the urban settings impede reliable centimeter-level localization at critical waterway sections. In this article, we propose a time-domain-optimized antenna array to provide high-precision 3D localization in these complex environments with minimal shore-side infrastructure by exploiting impulse-radio ultra-wideband (IR-UWB) technology. To enable joint distance and 2D angle-of-arrival (AoA) estimation, we present a novel IR-UWB antenna element that covers channels 5 and 7 of the IEEE 802.15.4z standard, serving as a building block for scalable multi-antenna systems. By leveraging the air-filled substrate-integrated-waveguide technology and adopting a multi-objective system-level optimization strategy, excellent performance is reconciled with a compact footprint and cost-effective fabrication. The 3D positioning accuracy of a 2 × 2 array is evaluated in stand-alone conditions and when installed on a metal plate mimicking a PSB’s metal hull, showing that all distance errors and 97 % of angular errors remain below 2 cm and 5°, respectively. Finally, three anchor nodes, each consisting of a 1 × 4 array connected to a Pozyx hardware platform, are installed on a vessel navigating in a narrow canal below a bridge in Ghent. With only one shore-side UWB beacon node deployed, 96 % of AoA estimation errors remain below 10°, while the distance error remains below 10 cm, proving good installed performance in harsh urban shipping environments.

With this contribution, the results of the measurement campaign performed with a synchronously distributed antenna array testbed operating at the center frequency of 3.686 GHz are presented. For the first time, to the best of the authors’ knowledge, the electric field distribution induced by coherent downlink transmission was experimentally assessed in the proximity of the target receiver using a calibrated electromagnetic field probe. This allowed to quantify the actual observed electric field gain and the shape of the electric field enhancement region around the target received. It was found that 16 transmitting antenna elements enhance the root-mean-square electric field level by about a factor of two, in a 2.5λ neighborhood of the target receiver. In addition, a possible disruption of the propagation environment due to the probe movement was assessed through the real-time channel state information feedback.

To support the most demanding new applications, beyond5G systems will more than ever rely on multi-antenna deployments and mm-wave spectrum. Unfortunately, due to its propagation properties, ultra-reliable high-data-rate mm-wave coverage seems elusive. Distributed antenna systems based on mm-wave-over-fiber constitute a strong candidate technology to unlock reliable mm-wave coverage, although the concept critically depends for a large part on the availability of cost-effective and power-efficient remote antenna units (RAUs). This contribution identifies two promising implementations for cost-effective and power-efficient beamforming at RAU-level, being a wideband Butler-matrix-based solution and a leaky-wave antenna (LWA), and validates them by means of system-level measurements. While the LWA-based RAU results in the lowest complexity with continuous beamsteering control, accurate control of the signal’s carrier frequency is required, which is unacceptable for many applications. Notwithstanding its slightly higher complexity, the Butler-matrix-based RAU is widely applicable and allows reuse of the same frequency spectrum for multiple sectors.