Passive Operating Research Articles

Optically Transparent Flexible Robust Circularly Polarized Antenna for UHF RFID Tags

Optically transparent flexible tag antennas are highly desired for some applications, where unobtrusiveness and capability of mounting on curved surfaces are required. On the other hand, circular polarization minimizes signal degradation due to polarization mismatch between the reader and tag antennas, thus ensuring good communication quality and accuracy. In this letter, we present an optically transparent and flexible radio frequency identification passive tag antenna operating in the ultrahigh frequency band and exhibits circular polarization. It is thin, lightweight, and completely encapsulated inside transparent polymer, which protects it against dust, water, heat, and mechanical stress. The tag antenna is made by utilizing highly flexible and transparent conductive-mesh-polymer composite through a simple and low-cost manufacturing process. The antenna design is based on a planar square ring. It achieves a measured maximum read range of about 8.3 m and approximately 47 MHz (885-932 MHz) 3 dB axial-ratio bandwidth (ARBW).

Significance of diffusion layers on the performance of liquid and vapor feed passive direct methanol fuel cells

Passive direct methanol fuel cell (pDMFC) has attracted the attention of scientists due to its high energy density. Under passive operating conditions, the properties of the diffusion layer significantly affect cell performance. In this study, the effect of the surface morphology, structure, permeability of diffusion layers (PTFE-treated carbon paper (CP) or carbon cloth (CC)) on the catalyst utilization, methanol, water fluxes, Faraday efficiency, and current discharge in pDMFC were investigated in liquid and vapor feed pDMFCs. Although catalyst utilization using the CP was higher than that using CC, the performance using the latter was enhanced in both liquid and vapor methanol feed. In liquid feed pDMFC, the optimum methanol concentration in the case of CC was 4 M, giving a power of 31 mW/cm2 compared to an optimum of 2 M and a power of 27 mW/cm2 in the case of CP. Although CP and CC have the same hydrophobicity, water droplet detachment from the cathode surface was easier in the case of CC compared to CP. In vapor feed pDMFC, using 100 wt% methanol at 0.25 V, the steady-state performance (29 mW/cm2) using CC was 190% of that using CP. Under active operation conditions, the performance of cell using CP is better than that using the CC due to the high catalyst utilization and the limited mass transfer effect.

Analysis of 25% duty-cycle up-conversion passive mixer for UWB transmitter

The performance of differential up-conversion passive mixer operating in the 3–5 GHz band for UWB transmitter driven by 25% duty-cycle clocks is studied and analyzed. A reasonably accurate LTI equivalent circuit accounting for harmonics is derived. We have demonstrated that the conversion gain, input and output impedances of the proposed LTI equivalent circuit matches those of the LTV up-conversion passive mixer. The LTI model can be used to define the reachable design space. The mixer input and output impedance can be tuned by varying resistor at the mixer output allowing for impedance match to connected circuits. We have shown how each design parameters impacts critical performance of the up-conversion passive mixer. Simulations of the proposed up-conversion passive mixer show −3.68 dB of conversion gain, 15.9 dBm of OIP3, 116.7dBm of OIP2 and a NF as low as 5.2 dB while consuming 1.5 pW. Furthermore linearity and ports isolation performances due to voltage threshold mismatch variation of ±60 mV shows an OIP3 greater than 15.85dBm and an LO_RF isolation smaller than −51.9 dB.

Low-Power Passive/Active UHF RFID Tag Transceiver with Frequency Locked On-chip Oscillator

A reconfigurable architecture is presented to be compatible with conventional passive operating mode and active mode for ultrahigh frequency (UHF) and radio-frequency identification (RFID) tag. The transceiver with frequency locked on-chip oscillator is proposed to increase the read range of RFID system and the lifetime of tag. The transceiver is fabricated in 0.18[Formula: see text][Formula: see text]m standard CMOS process with the active area of 0.246[Formula: see text]mm2. For passive mode, the sensitivity of tag is [Formula: see text][Formula: see text]dBm. For the active mode, the sensitivity is [Formula: see text][Formula: see text]dBm only consuming 1.2[Formula: see text][Formula: see text]W under the supply voltage of 0.8[Formula: see text]V. The output power is [Formula: see text][Formula: see text]dBm for active transmitting mode and the power consumption is 450[Formula: see text][Formula: see text]W under the supply voltage of 1[Formula: see text]V.

Coexistence of 5G With Satellite Services in the Millimeter-Wave Band

In this study, a new method is proposed to confirm the possibility of coexistence between the existing satellite services and potential fifth-generation (5G) cellular services in the millimeter-wave band according to the frequency-designation agenda of International Mobile Telecommunications (IMT)-2020 for 5G. To evaluate the accumulated interference power of numerous 5G systems distributed globally at a satellite receiver, we extend the satellite's interference reception area to the entire coverage area, from which only the land area is extracted using the geospatial terrain data of Earth in three dimensions. This enables more accurate interference assessment than conventional methods that only consider the footprint of the satellite's 3-dB beamwidth. We also place the IMT-2020 (5G) systems in the coverage area using the IMT-2020 parameters and modeling documents for the International Telecommunication Union's coexistence study. The propagation loss is modeled considering the clutter loss, building entry loss, and attenuation from atmospheric gases. Subsequently, we analyze the interference power received by a fixed satellite service (FSS) satellite operating in the same band and an Earth exploration satellite service (EESS) passive sensor operating in an adjacent channel. Our simulation shows that the FSS satellite receives up to 7.9dB more interference than that obtained from the existing method. Although this is a substantial difference, we find that the protection criteria is still satisfied. However, all EESS passive sensors do not meet the protection criteria in most scenarios, and additional frequency separation or interference mitigation techniques are required to protect these sensors. The proposed method is also applicable to the analysis of non-terrestrial network interference from airships, balloons, unmanned aerial vehicles, etc.

Tunable infrared asymmetric light transmission and absorption via graphene-hBN metamaterials

We theoretically prove in this paper that using planar multilayer graphene-hexagonal boron nitride (hBN) metamaterials (GhMMs) can yield ultrabroadband and high-contrast asymmetric transmission (AT) and asymmetric absorption (AA) of light. The AA and AT features are obtained in the far-infrared (FIR) and mid-infrared (MIR) regions for normally incident light with transverse magnetic polarization. Here, the GhMMs are integrated with two asymmetric gratings of Ge and are composed of alternating multilayers of graphene (11 multilayers) and hBN layers (10 layers). Moreover, the total subwavelength thickness of the hybrid structures is about 3 μm, being less than half of the free-space wavelength up to nearly 50 THz. This approach—which is similar to the one introduced by Xu and Lezec [Nat. Commun. 5, 4141 (2014)] for a passive hyperbolic metamaterial operating in the visible range—is based on the excitation of high-β modes of the GhMM with different transmission characteristics. In addition to being ultrabroadband and high-contrast, AT and AA features of the proposed GhMMs can be actively tuned by varying the chemical potential of graphene. Furthermore, it is shown that an on-off switching of AT factor at FIR and selective tunability at MIR frequencies can be obtained via varying μ. Due to its subwavelength and planar configuration and active operation, these multilayer graphene-hBN metamaterials with AT and AA characteristics hold promise for integration with compact optical systems operating in the MIR and FIR ranges and are suitable for applications such as optical diodes, sensors, and thermal emitters.

Development and Implementation of the Portable Operating Room Tracker App With Vital Signs Streaming Infrastructure: Operational Feasibility Study.

BackgroundIn the perioperative environment, a multidisciplinary clinical team continually observes and evaluates patient information. However, data availability may be restricted to certain locations, cognitive workload may be high, and team communication may be constrained by availability and priorities. We developed the remote Portable Operating Room Tracker app (the telePORT app) to improve information exchange and communication between anesthesia team members. The telePORT app combines a real-time feed of waveforms and vital signs from the operating rooms with messaging, help request, and reminder features.ObjectiveThe aim of this paper is to describe the development of the app and the back-end infrastructure required to extract monitoring data, facilitate data exchange and ensure privacy and safety, which includes results from clinical feasibility testing.MethodstelePORT’s client user interface was developed using user-centered design principles and workflow observations. The server architecture involves network-based data extraction and data processing. Baseline user workload was assessed using step counters and communication logs. Clinical feasibility testing analyzed device usage over 11 months.ResultstelePORT was more commonly used for help requests (approximately 4.5/day) than messaging between team members (approximately 1/day). Passive operating room monitoring was frequently utilized (34% of screen visits). Intermittent loss of wireless connectivity was a major barrier to adoption (decline of 0.3%/day).ConclusionsThe underlying server infrastructure was repurposed for real-time streaming of vital signs and their collection for research and quality improvement. Day-to-day activities of the anesthesia team can be supported by a mobile app that integrates real-time data from all operating rooms.

A Capacitive Pressure Sensor Based on Cofirable Ceramic/Glass Materials with LTCC Technology

Abstract Because of good thermal, electrical, and mechanical properties, low-temperature cofired ceramic (LTCC) has shown great potential in microelectronic applications. One of the most promising directions of LTCC technology development are integrating and packing sensors. In this article, a wireless passive capacitive pressure sensor operating in the MHz range based on cofiring of heterogeneous materials with LTCC technology is proposed, and the design, simulation, and fabrication of the sensor are demonstrated and discussed. It consists of a circular spiral inductor and a capacitor of two electrodes separated by a glass medium. Furthermore, a unique process of cofiring of heterogeneous materials was introduced to avoid deformation of the capacitive embedded cavity during lamination or sintering. The results show that the inductance of the inductor and the capacitance of the capacitor embedded in the sensor are .28 μH and 16.80 pF, respectively. The novel sensor has a sensitivity of approximately 847 Hz/MPa within the pressure range from atmospheric pressure to 100 MPa.

Active Distribution Networks Implications on Transmission System Stability

Renewable power generation sources are imposing new operational challenges for power systems around the world. The traditional passive operating conditions may change since the power flow can reverse its direction under certain conditions. When the penetration of distributed generation is low, the effects comprise only distribution system. On the other hand, high distributed generation penetration may harm the whole system. In this sense, the connection of these sources can cause a considerable impact on operation and planning of transmission and distribution systems. This paper focuses on the implications on transmission systems when active distribution networks are considered. Dynamic studies are performed to assess the effects in transmission systems of renewable power generation connected to the distribution systems, considering different models and several operating scenarios. The consequences of applying complete and equivalent models are also investigated. The analysis and approaches presented here demonstrate the active distribution networks may influence transmission system behavior and also support that choosing the adequate model to represent the system is essential according to the kind of investigation someone is performing.

Can resistant infections be perceptible in UK dairy farming?

This paper interrogates the claim that antimicrobial-resistant infections are rarely encountered in animal agriculture. This has been widely reiterated by a range of academic, policy and industry stakeholders in the UK. Further support comes from the UK's Animal and Plant Health Agency’s (APHA) passive clinical surveillance regime, which relies on veterinarians to submit samples for analysis and similarly reports low levels of resistance amongst key animal pathogens. Building on social science work on knowledge-practices of animal health and disease, and insights from emerging literature on non-knowledge or ‘agnotology’, we investigate the conditions shaping what is known about antimicrobial-resistant infections on farms. In so doing, we find that how on-farm knowledge is produced about resistant infection is concurrently related to domains of imperceptibility or what cannot be known in the context of current practices. The paper discusses the findings of ethnographic research undertaken on an East Midlands dairy farm that highlight the following specific findings. First, farmers and veterinarians, when observing instances of treatment failure, draw on an experiential repertoire that effaces resistances and instead foregrounds the complexities of host-pathogen interaction, or failings in human behaviour, over pathogen-antibiotic interactions. Second, the knowledge-practices of both farmers and veterinarians, although adept at identifying and diagnosing infectious disease are not equipped to make resistance perceptible. Third, this imperceptibility has implications for antibiotic use practices. Most notably, veterinarians anticipate resistance when making antibiotic choices. However, because of the absence of farm level knowledge of resistance this anticipatory logic is informed through the prevalence of resistance ‘at large’. The analysis has implications for the existing passive resistance surveillance regime operating in the dairy sector, which relies on veterinarians and farmers voluntarily submitting samples for diagnostic and susceptibility testing. In effect this entrenches farm level imperceptibility and effacement by farmers and veterinarians within the national dairy surveillance regime. However, we also highlight opportunities for providing farm specific knowledge of resistance through the anticipatory logic of veterinarians and a more active regime of surveillance.

All-fiber 2 μm thulium-doped mode-locked fiber laser based on MoSe2-saturable absorber

Abstract We demonstrate an all-fiber passive mode-locking laser operating in the 2 μm region that is implemented using a MoSe2-based saturable absorber (SA). A MoSe2-polyvinyl alcohol (PVA) SA is prepared with a modulation depth of 4.98%, a saturation intensity of 168.6 MW/cm2 and a nonsaturable loss of 29.6%. When the MoSe2-PVA SA was inserted into the fiber laser cavity, highly stable self-starting soliton pulse trains were generated with a center wavelength of 1943.35 nm and a 3 dB bandwidth of 4.38 nm. The pulse waveform has a sech2 profile with pulse duration of 980 fs. The fundamental repetition rate is 23.53 MHz and the signal-to-background ratio of the fundamental frequency ranges up to 65 dB. The production of stable and robust pulses using this laser indicates that the MoSe2-PVA SA is suitable for generation of 2 μm femtosecond ultrashort pulses.

Spiral resonator loaded S‐shaped folded dipole dual band UHF RFID tag antenna

AbstractA miniaturized UHF dual‐band passive RFID tag antenna operating in the 866‐869 and 950‐956 MHz bands is proposed. It consists of an S‐shaped Folded Dipole Antenna (FDA) resonating at 912 MHz, which is intermediary between the two required frequencies. To obtain dual‐band response perturbation method is employed. The electrical length of the FDA changes on loading a 2‐turn spiral resonator (2‐SR) to it. The 2‐SR splits the tag resonance at 912 MHz into two resonance frequencies (867 and 956 MHz). The proposed design is simulated using HFSS and then fabricated. Measured reflection coefficients at 867 and 956 MHz are −13.25 and −13.34 dB, respectively, exhibiting a 10 dB bandwidth of 11 MHz from 859 to 869 MHz and a 5 MHz 10 dB bandwidth from 953 to 957 MHz. Maximum read ranges of 5 m in 866‐869 MHz and 3.3 m in 950‐956 MHz band have been measured.

Optical Design and Analysis of the Submillimeter-Wave Instrument on JUICE

The submillimeter-wave instrument on the Jupiter icy moons explorer spacecraft is a passive dual-beam heterodyne radiometer operating in the frequency bands 530–625 and 1080–1275 GHz. The instrument will observe Jupiter's atmosphere as well as the atmosphere and surface properties of its moons. This paper presents the optical design and analysis of the instrument that has been carried out using Gaussian beam mode analysis and physical optics simulations. The optics consists of a 29-cm mechanically steerable off-axis Cassegrain telescope, relay optics, and two feedhorns. Frequency-independent operation of the 600-GHz channel is predicted by the simulations. The 1200-GHz channel shows some frequency dependency because of the selected feedhorn type. The steering of the telescope affects mainly its cross-polarization level. The manufacturing and mounting tolerances, as well as distortion and misalignment by thermoelastic effects, will cause the performance of a real instrument to deviate from that of an ideal one. Physical optics simulations combined with data from finite-element method simulations and measurements of optical surface profiles show that these factors affect, in particular, the instrument pointing. The induced pointing error is up to several arcminutes, whereas the specification is less than 0.5 arcmin. The pointing error can be reduced by adjusting the alignment of the telescope secondary mirror and the feedhorns.

Identification of unknown operating system type of Internet of Things terminal device based on RIPPER

Due to the vast popularity of sensors, cloud computing, mobile computing, and intelligent devices, the Internet of Things has seen tremendous growth in recent years. Operating system type recognition is the core technology of network security assessment. Due to inherit security problems of Internet of Things such as the situation of risk and threat of information, the operating system recognition seeks research attention for Internet of Things network security. In view of the current identification method of active operating system, it is prone to be detected by intrusion detection system. The operating system identification technology based on transmission control protocol/Internet protocol fingerprint library is more complicated than to distinguish the operating system types of unknown fingerprints. In this work, a passive operating system identification method based on RIPPER model is proposed. Also, it is compared with the existing support vector machine and C45 decision tree classification algorithms. Experiments reveal that RIPPER-based algorithm has better recognition accuracy and recognition efficiency.

The Passive Operating Mode of the Linear Optical Gesture Sensor

The study evaluates the influence of natural light conditions on the effectiveness of the linear optical gesture sensor, working in the presence of ambient light only (passive mode). The orientations of the device in reference to the light source were modified in order to verify the sensitivity of the sensor. A criterion for the differentiation between two states: "possible gesture" and "no gesture" was proposed. Additionally, different light conditions and possible features were investigated, relevant for the decision of switching between the passive and active modes of the device. The criterion was evaluated based on the specificity and sensitivity analysis of the binary ambient light condition classifier. The elaborated classifier predicts ambient light conditions with the accuracy of 85.15%. Understanding the light conditions, the hand pose can be detected. The achieved accuracy of the hand poses classifier trained on the data obtained in the passive mode in favorable light conditions was 98.76%. It was also shown that the passive operating mode of the linear gesture sensor reduces the total energy consumption by 93.34%, resulting in 0.132 mA. It was concluded that optical linear sensor could be efficiently used in various lighting conditions.

Modeled Martian subsurface elemental composition measurements with the Probing In situ with Neutron and Gamma ray instrument

AbstractThe Probing In situ with Neutron and Gamma ray (PING) instrument is an innovative application of active neutron‐induced gamma ray technology. The objective of PING is to measure the elemental composition of the Martian regolith. This manuscript presents PING's sensitivities as a function of the Martian regolith depth and PING's uncertainties in the measurements as a function of observation time in passive and active mode. The modeled sensitivities show that in PING's active mode, where both a pulsed neutron generator (PNG) and a gamma ray spectrometer (GRS) are used, PING can interrogate the material below the rover to about 20 cm due to the penetrating nature of the high‐energy neutrons and the resulting secondary gamma rays observed with the GRS. PING is capable of identifying most major and minor rock‐forming elements, including H, O, Na, Mn, Mg, Al, Si, P, S, Cl, Cr, K, Ca, Ti, Fe, and Th. The modeled uncertainties show that PING's use of a PNG reduces the required observation times by an order of magnitude over a passive operating mode where the PNG is turned off. While the active mode allows for more complete elemental inventories with higher sensitivity, the gamma ray signatures of some elements are strong enough to detect in passive mode. We show that PING can detect changes in key marker elements and make thermal neutron measurements in about 1 min that are sensitive to H and Cl.

Study of a harmonic mode lock stability under external continuous-wave injection

In this paper, we investigate experimentally the effect of an injected continuous external optical laser in a stable passive harmonic mode-locked fiber laser operating in the anomalous dispersion regime. Under specific conditions, the continuous-wave significantly increases the stability of the harmonic mode-locked regime. This occurs for a discrete set of wavelengths and below a critical injected power.

Molybdenum Disulphide Tape Saturable Absorber for Mode-Locked Double-Clad Ytterbium-Doped All-Fiber Laser Generation**Supported by the PPP Grant Scheme of University of Malaya under Grant No PG098-2014B.

We demonstrate the generation of passive mode-locked double-clad ytterbium-doped fiber laser operating in a 1-micron region. We prepare the saturable absorber from commercial crystal of molybdenum disulphide (MoS2). Without chemical procedure, the MoS2 is mechanically exfoliated by using a clear scotch tape. A few layers of MoS2 flakes are obtained on the tape. Then, a piece of 1 × 1 mm tape containing MoS2 thin flakes is inserted between two fiber ferrules and is integrated in the ring cavity. Stable mode-locking operation is attained at 1090 nm with a repetition rate of 13.2 MHz. Our mode-locked laser has a maximum output power of 20 mW with 1.48 nJ pulse energy. These results validate that the MoS2 has a broad operating wavelength which covers the 1-micron region, and it is also able to work in a high-power cavity.

3D MCRLB Evaluation of a UMTS-Based Passive Multistatic Radar Operating in a Line-of-Sight Environment

In this paper, the performance of a universal mobile telecommunication system (UMTS)-based passive multistatic radar in a line-of-sight (LoS) environment is studied. The presence of LoS component from the target considerably alters the received signal model, therefore, its characterization is necessary and is the main subject of this work where the transceivers and a target are localized in a three-dimensional Euclidean space. The probability density function (PDF) of the received signal in the presence of LoS is derived and the closed-form expressions of the modified Cramer–Rao lower bounds (MCRLBs) on the Euclidean coordinates of target's position and velocity are found. It is shown that modified Fisher information matrix (MFIM) is a combination of MFIMs due to non-LoS (NLoS) components and LoS component. With the aid of numerical examples, it is verified that by exploiting LoS, the target radar cross section (RCS) increases, which improves the accuracy of target's detection and parameter estimation. In addition, it is also shown that by exploiting LoS component, the performance limits of a waveform can be determined for a generalized radar cross section model (GRCSM), which provides the characterization of a waveform for a broader range of radar applications.

THz Absorption in Fabric and Its Impact on Body Scanning for Security Application

In recent years, body scanner technologies based on millimeter-wave and terahertz technologies have been shown to improve security in areas sensitive to terrorist attacks by detecting hazardous objects hidden underneath the clothing of people. Inevitably, useful devices have to provide an adequate compromise between spatial resolution limited due to diffraction and penetration through clothing. Within this context, the spectral absorption of a wide range of fabric, interference caused by the texture, and the effect of moisture within the fabric have to be considered. We have studied these effects by time-domain and Fourier transformation spectroscopy. The experimental findings are verified using a passive THz security camera operating in two frequency bands at 0.85 and 0.35 THz. The latter band was proven to be of superior use for security checks as it provides useful results even in cases of wet clothes.