This paper presents the design and implementation of efficient & compact flexible rectennas (antenna + rectifier) for wireless power transfer to wearable IoT sensor nodes at 24 GHz. Two different rectifier configurations i.e. shunt and voltage doubler have been analyzed for performance comparison. Experimental results of complete rectenna have also been demonstrated for conformal surfaces. The proposed flexible rectifiers is fabricated through conventional PCB manufacturing method. Measured RF-DC conversion efficiency of 31% and DC voltage of up to 2.4 V is achieved for 20 dBm input power across an optimal load resistance of 300Ω at 24 GHz.
This work explores the applicability of Resonant Tunnelling Diodes as active elements in two different amplifier configurations in the range 25 GHz-35 GHz, with a view of implementing scaled versions at W-band and beyond, as frontend narrow-band low-noise amplifiers. On-wafer S-parameter measurements are used to represent devices in simulation software for increased fidelity. Initial results are promising, showing close to 10 dB gain at 30 GHz.
Additive Manufacturing is capable of producing highly complex and personalised products. However, innovation in both material science and processing is required to achieve the performance, reliability and miniaturization of modern mass-produced electronic systems. This article presents a new digital fabrication strategy that combines 3D printing of high-performance polymers (polyetherimide) with light-based selective metallisation of copper traces through chemical modification of the polymer surface, and computer-controlled assembly of functional devices and structures. Using this approach, precise and robust conductive circuitry is fabricated across flexible and conformal surfaces omitting the need to connect and assemble separate circuits. To show how this process is compatible with existing electronic packaging techniques a range of modern components are solder surface mount assembled to selectively metalized bond pads. To highlight the potential applications stemming from this new capability, high frequency wireless communications, inductive powering and positional sensing demonstrators are manufactured and characterised. Furthermore, the incorporation of actuation is achieved through selective heating of shape memory alloys with a view towards routes towards folding and deployable 3D electronic systems. The results in this paper show how this process provides the required mechanical, electrical, thermal and electromagnetic properties for future real-world applications in the field of robotics, medicine, and wearable technologies.
This paper presents a new digitally driven manufacturing process chain for the production of high performance, three-dimensional RF devices. This is achieved by combining Fused Filament Fabrication of polyetherimide based polymer with selective light-based synthesis of silver nanoparticles and electrochemical deposition of copper. The resultant manufacturing method produces devices with excellent DC electrical resistivity (6.68 μΩ cm) and dielectric properties (relative permittivity of 2.67 and loss tangent of 0.001). Chemically modifying and patterning the substrate to produce the metallization overcomes many of the limitations of direct write deposition methods resulting in improved performance, adhesion and resolution of the antenna pattern. The fabricated demonstrators cover a broadband range of 0.1 GHz - 10 GHz and the measured results show a direct agreement with the simulated design over a wide frequency band. Overall the materials used as a substrate have a low relative permittivity and lower dielectric loss than FR-4, thereby making them well suited for antenna applications.
We demonstrate an air-core single-mode hollow waveguide that uses Bragg reflector structures in place of the vertical metal walls of the standard rectangular waveguide or via holes of the so-called substrate integrated waveguide. The high-order modes in the waveguide are substantially suppressed by a modal-filtering effect, making the waveguide operate in the fundamental mode over more than one octave. Numerical simulations show that the propagation loss of the proposed waveguide can be lower than that of classic hollow metallic rectangular waveguides at terahertz frequencies, benefiting from a significant reduction in Ohmic loss. To facilitate fabrication and characterization, a proof-of-concept 20 to 45 GHz waveguide is demonstrated, which verifies the properties and advantages of the proposed waveguide. A zero group-velocity dispersion point is observed at near the middle of the operating band. This work offers a step towards a novel hybrid transmission-line medium that can be used in a variety of functional components for broadband millimeter-wave and terahertz applications.
Large traffic network systems require handling huge amounts of data, often distributed over a large geographical region in space and time. Centralised processing is not then the right choice in such cases. In this paper we develop a parallelised Gaussian Mixture Model filter (GMMF) for traffic networks aimed to: 1) work with high amounts of data and heterogenous data (from different sensor modalities), 2) provide robustness in the presence of sparse and missing sensor data, 3) able to incorporate different models in different traffic segments and represent various traffic regimes, 4) able to cope with multimodalities (e.g., due to multimodal measurement likelihood or multimodal state probability density functions). The efficiency of the parallelised GMMF is investigated over traffic flows based on macroscopic modelling and compared with a centralised GMMF. The proposed GMM approach is general, it is applicable to systems where the overall state vector can be partitioned into state components (subsets), corresponding to certain geographical regions, such that most of the interactions take place within the subsets. The performance of the paralellised and centralised GMMFs is investigated and evaluated in terms of accuracy and complexity.
We demonstrate an air-core single-mode hollow waveguide that uses Bragg reflector structures in place of the vertical metal walls of the standard rectangular waveguide or via holes of the so-called substrate integrated waveguide. The high-order modes in the waveguide are substantially suppressed by a modal-filtering effect, making the waveguide operate in the fundamental mode over more than one octave. Numerical simulations show that the propagation loss of the proposed waveguide can be lower than that of classic hollow metallic rectangular waveguides at terahertz frequencies, benefiting from a significant reduction in Ohmic loss. To facilitate fabrication and characterization, a proof-of-concept 20 to 45 GHz waveguide is demonstrated, which verifies the properties and advantages of the proposed waveguide. A zero group-velocity dispersion point is observed at near the middle of the operating band. This work offers a step towards a novel hybrid transmission-line medium that can be used in a variety of functional components for broadband millimeter-wave and terahertz applications.
This paper presents, for the first time, a multimodal sensor for characterizing relative permittivity of plastic polymers by integrating in a single sensor (1) frequency-reconfigurable resonance technique at 98 and 100 GHz, and (2) 80-100-GHz broadband modified transmission-line technique. The sensor is designed based on a custom-made WR-10 waveguide featuring dual rectangular Complementary Split-Ring Resonators (CSRRs). By loading the CSRRs with a Material-Under-Test (MUT), the reflected and transmitted electromagnetic waves propagating inside the waveguide are changed depending on the dielectric properties of the material. Various plastic polymer materials, e.g. Polytetrafluoroethylene (PTFE), Polymethylmethacrylate (PMMA) and High-Density Polyethylene (HDPE), are characterized. The sensor in this paper offers various key advantages over any state-of-the-art material characterization techniques at millimeter-wave frequencies, e.g. multiple characterization techniques integrated in a single device, miniaturization, much higher tolerance to changes in the measurement environment, ease of design and fabrication, and better cost effectiveness.
This paper presents a novel approach to the design and fabrication of low-cost and high-gain aperture-coupled microstrip patch antenna (AC-MPA) arrays with improved radiation pattern for millimetre-wave applications such as simultaneous wireless information and power transfer (SWIPT) and Internet-of-Things (IoT) device connectivity. A higher-order mode substrate integrated waveguide (SIW) cavity is used to feed the MPA arrays through aperture coupling. The improved design approach is introduced and discussed in detail. Simulation and experimental results for 2 × 2 and 4 × 4 arrays are presented, demonstrating excellent agreement. Key performance metrics are side-lobe levels of less than −24 dB and −29 dB in the E-plane and −22 dB and −26 dB in the H-plane and realized gain of 11 dBi and 15 dBi for the 2 × 2 and 4 × 4 arrays respectively, at a design frequency of 30 GHz.
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