Reliability Analysis and Optimization of a Reconfigurable Matching Network for Communication and Sensing Antennas in Dynamic Environments through Gaussian Process Regression.

During the implementation of the Internet of Things (IoT), the performance of communication and sensing antennas that are embedded in smart surfaces or smart devices can be affected by objects in their reactive near field due to detuning and antenna mismatch. Matching networks have been proposed to re-establish impedance matching when antennas become detuned due to environmental factors. In this work, the change in the reflection coefficient at the antenna, due to the presence of objects, is first characterized as a function of the frequency and object distance by applying Gaussian process regression on experimental data. Based on this characterization, for random object positions, it is shown through simulation that a dynamic environment can lower the reliability of a matching network by up to 90%, depending on the type of object, the probability distribution of the object distance, and the required bandwidth. As an alternative to complex and power-consuming real-time adaptive matching, a new, resilient network tuning strategy is proposed that takes into account these random variations. This new approach increases the reliability of the system by 10% to 40% in these dynamic environment scenarios.

A compact SiGe D-band power amplifier for scalable photonic-enabled phased antenna arrays.

To address the rising demand for high-speed wireless data links, communication systems operating at frequencies beyond [Formula: see text] are being targeted. A key enabling technology in the development of these wireless systems is the phased antenna array. Yet, the design and implementation of such steerable antenna arrays at frequencies over [Formula: see text] comes with a multitude of challenges. In particular, the cointegration of active electronics at each antenna element poses a major hurdle due to the inherent space constraints in the array. This article proposes a novel scalable concept for opto-electronic phased antenna arrays operating at 140 GHz. It details the system architecture of a transmitter that enables the implementation of large scale, wideband, 2D steerable phased antenna arrays and presents the design and measurement of a compact SiGe power amplifier (PA) chip to be used as one of its key building blocks. The amplifier achieves a gain of 20 dB at 135 GHz, features a [Formula: see text] of 14.6 dBm and can support data rates up to 45 Gbps in a limited footprint of only 540µm × 550µm. This makes it one of the fastest, most powerful D-band power amplifiers in literature with a footprint compatible with [Formula: see text]-spaced phased array integration.

Air-filled SIW technology for mass-manufacturable and energy-efficient terahertz systems.

To accommodate the ever-growing data requirements in densely populated areas and address the need for high-resolution sensing in diverse next-generation applications, there is a noticeable trend towards utilizing large unallocated frequency bands above 100 GHz. To overcome the harsh propagation conditions, large-scale antenna arrays are crucial and urge the need for cost-effective, mass-manufacturable technologies. A dedicated Any-Layer High Density Interconnect PCB technology for highly efficient wireless D-band (110-170 GHz) systems is proposed. Specifically, the adapted stack accommodates broadband air-filled substrate-integrated-waveguide components for efficient long-range signal distribution and low-loss passives. The viability of the suggested technology platform is demonstrated by designing, fabricating and measuring several essential low-loss air-filled substrate-integrated-waveguide components, such as a dual rectangular filter, with a minimal insertion loss of 0.87 dB and 10 dB-matching within the (132.8-139.2 GHz) frequency band, and an air-filled waveguide with a routing loss of only 0.08 dB/mm and a flat amplitude variation within 0.01 dB/mm over the (115-155 GHz) frequency range. A broadband transition towards stripline, with a limited loss of 1.1 dB, is described to interface these waveguides with compactly integrated chips. A tolerance analysis is included as well as a comparison to the state of the art.

Fully Flexible Textile Antenna-Backed Sensor Node for Body-Worn UWB Localization.

A mechanically flexible textile antenna-backed sensor node is designed and manufactured, providing accurate personal localization functionality by application of Decawave's DW1000 Impulse Radio Ultra-Wideband (IR-UWB) Integrated Circuit (IC). All components are mounted on a flexible polyimide foil, which is integrated on the backplane of a wearable cavity-backed slot antenna designed for IR-UWB localization in Channels 2 and 3 of the IEEE 802.15.4-2011 standard (3744 MHz-4742.4 MHz). The textile antenna's radiation pattern is optimized to mitigate body effects and to minimize absorption by body tissues. Furthermore, its time-domain characteristics are measured to be adequate for localization. By combining the antenna and the bendable Printed Circuit Board (PCB), a mechanically supple sensor system is realized, for which the performance is validated by examining it as a node used in a complete localization system. This shows that six nodes around the body must be deployed to provide system coverage in all directions around the wearer. Even without using sleep mode functionalities, the measurements indicate that the system's autonomy is 13.3 h on a 5 V 200 mAh battery. Hence, this system acts as a proof of concept for the joining of localization electronics and other sensors with a full-textile antenna into a mechanically flexible sensor system.

Experimental Evaluation of UWB Indoor Positioning for Indoor Track Cycling.

Accurate radio frequency (RF)-based indoor localization systems are more and more applied during sports. The most accurate RF-based localization systems use ultra-wideband (UWB) technology; this is why this technology is the most prevalent. UWB positioning systems allow for an in-depth analysis of the performance of athletes during training and competition. There is no research available that investigates the feasibility of UWB technology for indoor track cycling. In this paper, we investigate the optimal position to mount the UWB hardware for that specific use case. Different positions on the bicycle and cyclist were evaluated based on accuracy, received power level, line-of-sight, maximum communication range, and comfort. Next to this, the energy consumption of our UWB system was evaluated. We found that the optimal hardware position was the lower back, with a median ranging error of 22 cm (infrastructure hardware placed at 2.3 m). The energy consumption of our UWB system is also taken into account. Applied to our setup with the hardware mounted at the lower back, the maximum communication range varies between 32.6 m and 43.8 m. This shows that UWB localization systems are suitable for indoor positioning of track cyclists.

Compact and wideband transmit opto-antenna for radio frequency over fiber.

An advanced transmit remote opto-antenna unit is proposed that accomplishes impedance matching between a photodetector and a low-profile antenna in a specified frequency bandwidth, without requiring an area-consuming matching network. This results in a highly compact design, which also avoids the losses and spurious radiation by such an electrically large matching circuit. Instead, the photodetector is almost directly connected to the antenna, which is designed as a conjugate load, such that the extracted and radiated power are optimized. The required input impedance for the antenna is obtained by adopting a half-mode air-filled substrate-integrated-waveguide topology, which also exhibits excellent radiation efficiency. The proposed unit omits electrical amplifiers and is, therefore, completely driven by the signal supplied by an optical fiber when deployed in an analog optical link, except for an externally supplied photodetector bias voltage. Such a highly cost-effective, power-efficient and reliable unit is an important step in making innovative wireless communication systems, which deploy extremely dense attocells of 15 cm × 15 cm, technically and economically feasible. As a validation, a prototype, operating in the Unlicensed National Information Infrastructure radio bands (5.15 GHz-5.85 GHz), is constructed and its radiation properties are characterized in free-space conditions. After normalizing with respect to the optical source's slope efficiency, a maximum boresight gain of 12.0 dBi and a -3 dB gain bandwidth of 1020 MHz (18.6 %) are observed.

Wi-PoS: A Low-Cost, Open Source Ultra-Wideband (UWB) Hardware Platform with Long Range Sub-GHz Backbone.

Ultra-wideband (UWB) localization is one of the most promising approaches for indoor localization due to its accurate positioning capabilities, immunity against multipath fading, and excellent resilience against narrowband interference. However, UWB researchers are currently limited by the small amount of feasible open source hardware that is publicly available. We developed a new open source hardware platform, Wi-PoS, for precise UWB localization based on Decawave's DW1000 UWB transceiver with several unique features: support of both long-range sub-GHz and 2.4 GHz back-end communication between nodes, flexible interfacing with external UWB antennas, and an easy implementation of the MAC layer with the Time-Annotated Instruction Set Computer (TAISC) framework. Both hardware and software are open source and all parameters of the UWB ranging can be adjusted, calibrated, and analyzed. This paper explains the main specifications of the hardware platform, illustrates design decisions, and evaluates the performance of the board in terms of range, accuracy, and energy consumption. The accuracy of the ranging system was below 10 cm in an indoor lab environment at distances up to 5 m, and accuracy smaller than 5 cm was obtained at 50 and 75 m in an outdoor environment. A theoretical model was derived for predicting the path loss and the influence of the most important ground reflection. At the same time, the average energy consumption of the hardware was very low with only 81 mA for a tag node and 63 mA for the active anchor nodes, permitting the system to run for several days on a mobile battery pack and allowing easy and fast deployment on sites without an accessible power supply or backbone network. The UWB hardware platform demonstrated flexibility, easy installation, and low power consumption.

A Novel Manufacturing Process for Compact, Low-Weight and Flexible Ultra-Wideband Cavity Backed Textile Antennas.

A novel manufacturing procedure for the fabrication of ultra-wideband cavity-backed substrate integrated waveguide antennas on textile substrates is proposed. The antenna cavity is constructed using a single laser-cut electrotextile patch, which is folded around the substrate. Electrotextile slabs protruding from the laser-cut patch are then vertically folded and glued to form the antenna cavity instead of rigid metal tubelets to implement the vertical cavity walls. This approach drastically improves mechanical flexibility, decreases the antenna weight to slightly more than 1 g and significantly reduces alignment errors. As a proof of concept, a cavity-backed substrate integrated waveguide antenna is designed and realized for ultra-wideband operation in the [5.15-5.85] GHz band. Antenna performance is validated in free space as well as in two on body measurement scenarios. Furthermore, the antenna's figures of merit are characterized when the prototype is bent at different curvature radii, as commonly encountered during deployment on the human body. Also the effect of humidity content on antenna performance is studied. In all scenarios, the realized antenna covers the entire operating frequency band, meanwhile retaining a stable radiation pattern with a broadside gain above 5 dBi, and a radiation efficiency of at least 70%.