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Pattern Distributed Pins in Half-mode Groove Gap Waveguide for Stable Performance and Low Cost
No full textIn this paper, a new concept of pattern distributed pin structure is proposed to improve the stability of the phase performance when there is a misalignment in a half-mode groove gap waveguide (HM-GGW) and therefore reduce the manufacture cost. To demonstrate the advantages of the pattern distributed pin structure, a non-collinear pin pattern and a rotated pin pattern are proposed and applied to a straight HM- GGW and a 90-deg bend HM-GGW. The dispersion diagram and simulation results show that the pattern distributed pin structure has a similar stop-band characteristics as the standard pin structure with much less sensitivity to misalignments between the upper pins and the lower wave-guiding structure. By applying a proper pattern distributed pin structure, a larger flexibility is obtained in design of GW devices and the manufacture cost can be reduced significantly
A Multi Beam Slot Array Antenna Fed by Contactless Multi-Layered 4x8 Buttler Matrix Using Gap Waveguide Technology for 60GHz Fixed Wireless Access Applications
No full textA multi layered multi beam antenna design based on gap waveguide technology is presented in this work. In the proposed antenna a 8x10 slot array is used as the antenna aperture, however the beam forming network (BFN) consists of a multi layered 4x8 Buttler matrix realized using both ridge gap waveguide (RGW) and groove gap waveguide (GGW) technologies. The proposed structure is composed of five unconnected layers which can be simply assembled using screws and guiding pins without any need of electrical contact in accordance with the contact-less assembly feature of gap waveguide technology. The designed antenna shows proper radiation performance including low side lobes and flat gain response which can be applied for access points in fixed wireless communications operating at 60GHz. Also the S11 remains below -10dB for the input ports within the frequency range of 5964-GHz. The simulated gain for the array is 25dBi at bore sight and 22 dBi when the +/- 45 degrees beam is excited
Automotive RADAR Planar Antenna Optimization Based on Conformal Transformation Optics
No full textA novel approach to mitigate diffraction effects from finite ground planes in antenna design is presented. The method is based on the conformal transformation optics. A computational framework has been developed to optimize the shape of the ground plane since it has a great impact on the beam ripple and width of the radiation pattern of an antenna. Due to the limited thickness of the outer wall of slotted waveguide antennas, it is not possible to shape this outer wall, which acts as the ground plane of the antenna. Conformal transformation optics presents a solution to virtually add a deformation without needing to change the physical shape of the ground plane. Although conformal transformation optics can also be applied to transverse-magnetic waves, large fluctuations in the dielectric constant with respect to the wavelength cannot be supported in practice. In order to mitigate this problem, we have proposed a rescaling of the dielectric constant. Furthermore, we derive the connection between conformal transformation optics and transverse electromagnetic modes, which serve as a tool for joint optimization of the radiation pattern together with the conformal transformation. This method is then used to optimize the radiation pattern of a slot antenna and evaluated for increasing curvature within the conformal transformation.Numerical computations have shown promising results, i.e. a reduction of the farfield ripple from 1.92 dB to 0.64 dB at a half-power beam-width of 112\ub0 at 77 GHz. This is a promising result for designing automotive radars with a wide field of view, especially, for advanced driver-assistance systems used in the corner radars. This will contribute to further improving safety on the roads
Automated Extraction of Grammar Optimization Rule Configurations for Metamodel-Grammar Co-evolution
No full textWhen a language evolves, meta-models and associated grammars need to be co-evolved to stay mutually consistent. Previous work has supported the automated migration of a grammar after changes of the meta-model to retain manual optimizations of the grammar, related to syntax aspects such as keywords, brackets, and component order. Yet, doing so required the manual specification of optimization rule configurations, which was laborious and error-prone. In this work, to significantly reduce the manual effort during meta-model and grammar co-evolution, we present an automated approach for extracting optimization rule configurations. The inferred configurations can be used to automatically replay optimizations on later versions of the grammar, thus leading to a fully automated migration process for the supported types of changes. We evaluated our approach on six real cases. Full automation was possible for three of them, with agreement rates between ground truth and inferred grammar between 88% and 67% for the remaining ones
A Survey on Measuring Cognitive Workload in Human-Computer Interaction
No full textThe ever-increasing number of computing devices around us results in more and more systems competing for our attention, making cognitive workload a crucial factor for the user experience of human-computer interfaces. Research in Human-Computer Interaction (HCI) has used various metrics to determine users\u27 mental demands. However, there needs to be a systematic way to choose an appropriate and effective measure for cognitive workload in experimental setups, posing a challenge to their reproducibility. We present a literature survey of past and current metrics for cognitive workload used throughout HCI literature to address this challenge. By initially exploring what cognitive workload resembles in the HCI context, we derive a categorization supporting researchers and practitioners in selecting cognitive workload metrics for system design and evaluation. We conclude with three following research gaps: (1) defining and interpreting cognitive workload in HCI, (2) the hidden cost of the NASA-TLX, and (3) HCI research as a catalyst for workload-aware systems, highlighting that HCI research has to deepen and conceptualize the understanding of cognitive workload in the context of interactive computing systems
Single Layer Antenna based on Gap Waveguide Technology with Dual-Circular Polarization for 60-GHz Band
No full textA dual-circularly polarized antenna element based on E-plane groove gap waveguide (GGW) for 60 GHz applications is presented in this work. The simulated return loss of the antenna is better than -10 dB for both polarizations in the working frequency bandwidth of antenna covering from 58 GHz to 62 GHz. The axial ratio of the proposed antenna is better than 2.5 dB in the whole bandwidth. The simulation results prove that the proposed antenna element is a good candidate to design larger array with dual circular polarization for different wireless applications at millimeter wave frequency range
Compact lithium niobate microring resonators in the ultrahigh Q/V regime
Get PDFLithium niobate (LN) is a promising material for future complex photonic-electronic circuits, with wide applications in such fields as communications, sensing, quantum optics, and computation. LN took a great stride toward compact photonic integrated circuits (PICs) with the development of partially etched LN on insulator (LNOI) waveguides. However, integration density is still limited for future highly compact PICs, owing to the partial etching nature of their waveguides. Here, we demonstrate a fully etched LN PIC platform, which, for the first time to our knowledge, simultaneously achieves ultralow propagation loss and compact circuit size. The tightly confined fully etched LN waveguides with smooth sidewalls allow us to bring the bending radius down to 20 μm (corresponding to 1 THz free spectral range). We have achieved compact high\ua0Q\ua0microring resonators with\ua0Q/V\ua0of 8.7
7 104 μm−3, almost one order of magnitude larger than previous demonstrations. The statistical mean propagation losses of our LN waveguides is 8.5 dB/m (corresponding to a mean\ua0Q\ua0factor of 4.9
7 106), even with a small bending radius of 40 μm. Our compact and ultralow-loss LN platform shows great potential in future miniaturized multifunctional integration systems. As complementary evidence to show the utility of our platform, we demonstrate soliton microcombs with an ultrahigh repetition rate of 500 GHz in LN
Transient tyre models with a flexible carcass
Get PDFThe accuracy of transient tyre models may be largely improved by considering the flexibility of the tyre carcass. Several formulations, whereby the unsteady behaviour of the tyre is approximated using linear or nonlinear systems of ordinary differential equations (ODEs), are already available in the literature. However, when the tread behaviour is described using a distributed representation, that is, in terms of partial differential equations (PDEs), the inclusion of even the simplest model to represent the deformation of the tyre carcass leads to rather involved PDE or interconnected PDE-ODE systems, with nonlocal and boundary terms. Such descriptions require detailed analyses that have not been attempted so far. Therefore, this paper investigates the salient properties of the classic brush and LuGre-brush models considering the effect of a flexible carcass. For both formulations, the existence and uniqueness of the solution are discussed. For the standard version of the brush models, a closed-form solution is provided under the assumption of vanishing sliding, whereas the case of limited friction is explored only qualitatively. Concerning the LuGre-brush variant, the preliminary intuition gained from the analysis of the distributed representation is effectively used to develop approximated lumped formulations to be used in control-oriented applications
Performance of the IVS R1 and R4 sessions
No full textThe International VLBI Service for Geodesy and Astrometry (IVS) has observed the weekly IVS-R1 (R1) and IVS-R4 (R4) series of sessions since 2002. These regular series are generally stable in the sense that the networks were designed to be similar from week to week. The uniformity of these series has allowed researchers to conduct many scientific investigations. The IVS also observes with other networks that allow continued sampling of data from all VLBI stations, but the R1 and R4 observing sessions are a dominant part of overall VLBI observing accounting for 1841 sessions out of a total of 3129 24-hour sessions from 2002.0 to 2020.0 (where the last R1 and R4 in 2019 was on December 30 and December 26, respectively). In this paper, we investigate the evolution of these series in terms of their observing networks. We also discuss the construction of the R1 and R4 networks and the scheduling of these sessions. The performance of these networks in terms of the formal precision of polar motion have improved by factors of 2–3 over the period from 2002.0 to 2018.0. UT1 precision improved by a factor of about 1.2–1.5. The main reason for this improvement is the increased size of the networks. We also discuss the effect on this improvement arising from changes in the data rate and the number of observed sources. There is some degradation in performance after 2018 that is most likely due to a decline in the number of available network stations