Dual-mode Operation Research Articles

Planar Circularly Polarized Antenna With Bandpass Filtering Response Based on Dual-Mode SIW Cavity

In this study, a novel single-fed low-profile circularly polarized (CP) antenna with a bandpass filtering response is proposed. It is based on a planar substrate integrated waveguide (SIW) dual-mode (TE102/TE201) cavity. When the vias on the edge become sparse, the electromagnetic wave leaks out while maintaining a good dual-mode filtering response. The antenna is folded in order to reduce the aperture size to form an un-splitted radiation beam with small side lobes. Owing to a rotated dual-mode operation, the fields escaping from four sets of sparse vias are approximately of equal amplitude with a progressive phase difference of 90° in sequence. CP radiation is thus achieved when the four orthogonal half-mode radiation patches are excited by the leaking field. By adopting a single feeding with two pairs of asymmetrical shorting pins, the peak gain is improved significantly and a 3 dB axial ratio (AR) response with two minima is obtained simultaneously. Long metal walls and rectangular slots are introduced to fold the current flow and change the wave direction. Consequently, sidelobe level is significantly reduced and the antenna directivity is enhanced. To verify this novel design idea, an antenna prototype with a height of $0.036\lambda _{0}$ has been fabricated using the multilayer PCB process and measured in a near-field microwave chamber. Measured results are well consistent with the simulation, demonstrating CP radiation with a flat/high gain and good filtering performance.

Wearable Dual-Band and Dual-Polarized Textile Antenna for On- and Off-Body Communications

A wearable all-textile microstrip patch antenna (MPA) operating in the dual bands of medical body area network (2.36–2.40 GHz) and WiMAX (3.4–3.6 GHz), is proposed for body-centric communications. The omnidirectional radiation pattern with linear polarization for on-body link and unidirectional radiation pattern with circular polarization for off-body link are achieved by introducing reactance loading into MPA. Notably, two pairs of shorting pins are employed to tune the TM10 mode of MPA and generate a new mode of TM00, and by adjusting the spacing and radii of shorting pins, the required dual-band and dual-mode operation is achieved. Moreover, due to the adoption of textile (i.e., wool felt) as substrate and nylon conductive fabric as conductor, the antenna is flexible, totally conforming to the human body. The proposed MPA, with the dimensions of 70 mm × 70 mm × 2 mm (0.56λ0 × 0.56λ0 × 0.016λ0 at 2.38 GHz), was fabricated and characterized. The measured results show that the reflection coefficient, radiation pattern, and gain of the antenna are slightly affected by structural deformation and human body loading. With merit characteristics, the proposed design can be well applied to wearable medical applications.

Broadband and High Efficiency Rectifier Design Based on Dual-mode Operation for RF Ambient Energy Harvesting

Broadband and High Efficiency Rectifier Design Based on Dual-mode Operation for RF Ambient Energy Harvesting

Wideband microstrip‐fed slot antenna with end‐fire radiation under dual‐resonant modes

In this paper, a microstrip-fed narrow slot antenna with end-fire radiation and expanded bandwidth under dual-resonant modes operation is proposed. At first, the open-ended slot radiator is studied and used to effectively suppress all the undesired even-order modes, reduce the antenna size, and form up the end-fire radiation pattern simultaneously. After that, by symmetrically introducing a pair of slot stubs near the electric-field distributions nodal lines of its second odd-order mode, the resonant frequency of second odd-order mode is gradually moved down. As such, the first and second odd modes could be effectively moved in proximity to each other, thus resulting in the improved impedance bandwidth of the slot antenna under dual-mode operation. To validate the predicted results, the proposed wideband microstrip-fed slot antenna is in final fabricated and measured. Both simulated and measured results are derived with good agreement. Measured results indicate that the impedance bandwidth of the slot antenna has achieved an immense enhancement up to about 25.5% (2.43-3.14 GHz). Moreover, the front-to-back ratio (FBR) beyond 6.0 dB has been successfully obtained across the whole operating band for end-fire radiation.

Design Procedure for Bandpass Filters Based on Integrated Coaxial and Rectangular Waveguide Resonators

In this article, we present a novel bandpass filter based on dual-mode resonators. The dual-mode operation is based on integrated coaxial and rectangular waveguide cavities. Furthermore, we also discuss a systematic design procedure for the selection of the dimensions of the various constituent elements of the filter, which is based on the well-known aggressive space mapping technique. The design of a five-pole bandpass filter operating in the X-band is discussed in detail, including the measured data. The comparison between simulations and measurement shows very good agreement, thereby fully validating both the new filter structure and the design procedure.

Comparative assessment of biogas and producer gas with diesel in a twin cylinder dual-fuel diesel engine

The present work describes the preparation of producer gas and biogas from waste biomass material and its application in a twin cylinder dual-fuel diesel engine to study their performance and emission characteristics by the fractional replacement of fossil diesel in dual-fuel mode. Experiments are carried out both in diesel mode as well as dual-fuel mode operation under different engine loads. Comparative outcomes of performance and emission parameters for both modes of operations are presented. The study reveals that dual-mode operations show lower performance characteristics but better control of emission parameters like nitric oxide (NO) and smoke opacity compared to diesel mode. The hydrocarbon emission of producer gas-diesel and biogas-diesel was found to be 65.8% and 109.7% respectively, higher than diesel mode at the optimum load of 8 kW. Similarly, brake thermal efficiency of dual-mode operation of producer gas-diesel and biogas-diesel was 2.47% and 1.67%, respectively, lower than diesel mode. The pilot fuel savings percentage achieved was 85.5% in biogas-diesel and 83% in producer gas-diesel operation at the same loading condition. Further, comparing biogas with producer gas, it was observed that some of the emission parameters like carbon monoxide CO and NO were better controlled by biogas than producer gas whereas, HC and smoke emissions were better controlled by producer gas than biogas.

High Energy Efficient System Design for Incubation Process and Cooling of Yoghurt

Food processing studies are important for both efficient use of energy and to obtain quality products. Yoghurt is a dairy product which consumes widely. Yoghurt producing facilities consumes high energy and run at low efficiency due to their traditional production methods. In order to produce quality yoghurt, pasteurized milk should be kept at 42-45 oC for 3-5 hours depending on the yeast type, this process called as incubation. After the incubation process, produced yoghurt must be cooled down to 20 oC in two hours depending on the package size of yoghurt. In conventional yoghurt production facilities, required heating and cooling are applied independently and this approach causes high energy consumptions, waste heat and the inefficient use of energy. In this study, a combined system consisting of a heat pump and a heat storage unit which is capable of the simultaneously heating and/or cooling application independently of each other is designed to ensure higher energy performance and efficiency. Thus, the required energy for heat transfer from the evaporator and cooling after the incubation process was ensured from the stored ice and, independently of the weight of the product, 64/68 units of energy (depending of refrigerant) were gained for each 100 units of required heating energy.The coefficient of performance (COP) of the system using R410a and R134a for heating, cooling and dual operation modes were calculated as 2.83, 1.83, 4.66 and 3.16, 2.16, 5.31, respectively. Energy costs for heat pump and conventional natural gas-fuel-oil boilers were compared. High energy efficiency and low energy consumption have been provided with the presented design, and suggestions for use for production facilities are given.

Dual Circularly Polarized Array Antenna Based on Corporate Feeding Network in Square Waveguide Technology

In this communication, the design and fabrication of a Ku -band antenna array is presented for dual circular polarization, using a corporate feeding network (CFN) with orthogonal dual-mode operation. A four-way CFN in square waveguide technology is implemented to uniformly illuminate the antenna array. Each of the two propagating modes in the square waveguide excites orthogonal polarizations in the antenna. A dual circularly polarized radiating element is used for the dual-polarized array. Consequently, the link capacity can be doubled by using orthogonal polarizations in a compact and low-loss antenna system. Prototypes have been fabricated by conventional machining and they have been experimentally tested. A 90% total efficiency and matching coefficient better than −10 dB have been obtained in the frequency band between 16.5 and 17.5 GHz for the dual circularly polarized antenna. Further simulations have proven the validity of this topology for larger dual-polarized planar arrays.

Polymer based thermoelectric nanocomposite materials and devices: Fabrication and characteristics

Organic thermoelectric (TE) materials capitalize on advantages such as low thermal conductivity, low-cost, eco-friendly, versatile processability, light-weight, mechanical flexibility, roll-to-roll production, which are advantageous for the development of portable and wearable self-powered electronics. On the negative side, the figure-of-merit of polymer TE materials is low, mainly owing to typical low electrical conductivity. Various efforts have been made to enhance the TE performance of organic TE materials, i.e. chemical or electrochemical doping, modification of molecular structure, and fabrication of polymer-based composites or blends, which is the simplest and most cost-effective method for modifying polymer properties. Solution-processed polymer/inorganic or organic hybrids pave the way for formulation of functional TE inks/paste which can be used to fabricate large scale cost-effective manufacturing of TE generators. In this review, we briefly summarize the TE properties of conjugated polymers, and focus on recent developments in polymer/carbon nanofillers (e.g. CNT, graphene, GO) composites and polymer/inorganic TE nanoparticles composites along with preparation methods and thermoelectric performance. Finally, we cover recent advances in the development of functional TE inks, processing techniques, and their usage in device fabrication using various printing techniques and review device output characteristics. • Covers hot topic of thermoelectric materials & devices, suitable for energy harvesting to power IoT sensors and devices. • Review & analysis on advances on enhanced thermoelectric properties of polymer based nanocomposites (CNT, graphene, NP, NW). • Analyzing effect of composite processing mechanisms, and also interchain and cross-domain transport on properties. • Recent progress in the fabrication methods of a variety of functional nanocomposite inks/pastes for different printers. • Analysis of recent nanocomposites TE devices and their output characteristics in dual-mode or single-mode operation.

Deep-Learning-Based Deconvolution of Mechanical Stimuli with Ti3C2Tx MXene Electromagnetic Shield Architecture via Dual-Mode Wireless Signal Variation Mechanism.

Passive component-based soft resonators have been spotlighted in the field of wearable and implantable devices due to their remote operation capability and tunable properties. As the output signal of the resonator-based wireless communication device is given in the form of a vector (i.e., a spectrum of reflection coefficient), multiple information can, in principle, be stored and interpreted. Herein, we introduce a device that can deconvolute mechanical stimuli from a single wireless signal using dual-mode operation, specifically enabled by the use of Ti3C2Tx MXene. MXene's strong electromagnetic shielding effect enables the resonator to simultaneously measure pressure and strain without overlapping its output signal, unlike other conductive counterparts that are deficient in shielding ability. Furthermore, convolutional neural-network-based deep learning was implemented to predict the pressure and strain values from unforeseen output wireless signals. Our MXene-integrated wireless device can also be utilized as an on-skin mechanical stimuli sensor for rehabilitation monitoring after orthopedic surgery. The dual-mode signal variation mechanism enabled by integration of MXene allows wireless communication systems to efficiently handle various information simultaneously, through which multistimuli sensing capability can be imparted into passive component-based wearable and implantable electrical devices.

Hodoscope with Timepix detectors for PilsenCube2 cubesat

The contribution describes the design of Timepix-based hodoscope for cubesat applications, such as PilsenCube2, developed by the University of West Bohemia. The hodoscope is composed of two Timepix detectors with silicon thickness of 300μm, placed in back-to-back arrangement and rotated relative to each other by 90°, forming a telescope set-up. A copper separator is placed between two detectors to distinguish electrons and protons. The payload hardware and firmware are designed to support single detector operation as well as dual detector operation mode, in which particle coincidence detection is possible. The hodoscope electronic has been designed with respect to harsh radiation environment present in LEO (Low Earth Orbit). The device involves independent radiation hardened power supplies, including bias high voltage supply (up to 250 V) and auxiliary threshold reference DAC for each Timepix detector. Considering highly limited achievable data throughput between the CubeSat and the ground control station, advanced on-board data processing has been developed to reduce the size of transmitted data. The on-board data processing is provided by the radiation hardened SoC (System on Chip) Smartfusion2.

AFM Microcantilever With a Collocated AlN Sensor-Actuator Pair: Enabling Efficient Q-Control for Dynamic Imaging

This manuscript presents a novel microcantilever with an embedded piezoelectric sensor-actuator pair for dynamic atomic force microscopy (AFM). The transducer pair is constructed from a two-layered AlN stack. Stacking the piezoelectric transducers in this manner leads to a minimal feedthrough from actuation to sense electrode, granting a high dynamic range frequency response for dynamic mode AFM. The cantilever’s design allows for dual mode operation at 1st and 2nd resonance modes. High resolution tapping mode imaging results are reported, while the cantilever is operated at these modes. A feedback control loop is used to modify quality factor of the 1st mode of the cantilever, using a positive position feedback (PPF) controller. A faster response time is achieved by reducing the ${Q}$ -factor, enabling the cantilever to track the topography at a higher scan rate. Results of bimodal AFM imaging are reported, using amplitude changes of the 1st mode for surface topography, while material properties are encoded in phase changes of the 2nd mode. [2020-0096]

Numerical Performance Analysis of a Supersonic Combustor at Mach 8 Flight Off-Design Conditions

A numerical investigation of the performance of a supersonic combustor designed for a flight Mach 8 is presented. Numerical simulations are used to assess the characteristics and operational limits of the combustor at design and off-design conditions. The combustor design point corresponds to the cruise condition at a Mach number of 8 and an altitude of 30 km. Off-design conditions correspond to a Mach number of 8 at 28 km altitude and a Mach number of 6 at 26 km altitude. Each off-design condition was investigated at three different angles of attack: 2, 0, and . For constant flight Mach number and altitude, the variation of the angle of attack showed significant influence on the performance of the combustor, mainly on the ignition length. Flying at a negative angle of attack resulted in intense combustion and reduced ignition length. For the Mach 6 off-design condition, a dual-operation mode (ramjet–scramjet) with regions of subsonic combustion was observed. At such condition, it was possible to extend the operation of the combustor and avoid subsonic combustion regions by varying the angle of attack to a positive value. For a constant flight Mach number and altitude, the variation of the angle of attack showed an interesting mechanism to control combustion.

Improved multifunctional controller for power quality enhancement in grid integrated solar photovoltaic systems

PurposeThis paper aims to propose an improved multifunctional control strategy for achieving real, reactive power flow control and the mitigation of power quality issues in grid integrated photovoltaic (GIPV) systems.Design/methodology/approachThe paper proposes a dual stage, three phase, multifunctional GIPV system with modified instantaneous reactive power (IRP) theory-based and modified synchronous reference frame (SRF) theory-based control algorithms for reference template generation with continuous load power requirement tracking. The control structure is designed so as to impart virtual distribution static compensator functionality to the photovoltaic inverter. The dual mode operation in active filter and renewable power injection modes provides enhanced capability to the GIPV system. A comprehensive evaluation of the dynamic behaviour of the GIPV system is carried out for various conditions of irradiance and load under MATLAB/Simulink platform. The performance comparison is done considering an uncompensated system and the GIPV system with both proposed control algorithms.FindingsThe extensive simulation results demonstrate that the proposed modified SRF theory-based multifunctional control strategy shows superior performance in real and reactive power flow control; reduction in real and reactive burden of the utility grid; and regulation of dc bus voltage under varying scenarios of irradiance and load. Furthermore, there is improvement of grid power factor and reduction in total harmonic distortion of grid currents in compliance with the IEEE 519 standard even with highly non-linear loads at the point of common coupling.Originality/valueThe proposed modified SRF theory-based multifunctional controller offers a viable solution for power quality enhancement as well as the realization of effective real and reactive power flow control in GIPV systems. Thus, the penetration level of distributed generation can be increased in this era of global energy crisis.

An Improved CMUT Structure Enabling Release and Collapse of the Plate in the Same Tx/Rx Cycle for Dual-Frequency Acoustic Angiography.

This study demonstrates, in detail, the potential of using capacitive micromachined ultrasonic transducers (CMUTs) for acoustic angiography of the microvasculature. It is known that when ultrasound contrast agents (microbubbles) are excited with moderate acoustic pressure around their resonance (2-4 MHz), they produce higher order harmonics (greater than third harmonic) due to their nonlinear behavior. To date, the fundamental challenge has been the availability of a transducer that can generate the transmit signals to excite the microbubbles at low frequencies and, in the same cycle, confocally detect harmonics in the higher frequencies. We present a novel device structure and dual-mode operation of a CMUT that operates with a center frequency of 4.3 MHz and 150% bandwidth in the conventional mode for transmitting and a center frequency of 9.8 MHz and a 125.5% bandwidth in collapse mode for receiving. Output pressure of 1.7 MPapp is achieved on the surface of a single unfocused transducer. The mechanical index at the transducer surface is 0.56. FEM simulations are performed first to show the functionality of the proposed device, and then, the device fabrication is described in detail. Finally, we experimentally demonstrate the ability to detect the microbubble signals with good contrast, and the background reflection is adequately suppressed, indicating the feasibility of the presented approach for acoustic angiography.

Autonomous Model Predictive Controlled Smart Inverter With Proactive Grid Fault Ride-Through Capability

This article presents an autonomous model predictive controlled smart photovoltaic (PV) inverter with proactive grid fault-ride through capability. The proposed smart inverter control features decoupled active and reactive power. It can seamlessly switch between the anticipated modes of operation based on grid condition or grid operator command. The smart inverter autonomously adjusts its active and reactive power set-points according to the grid condition, it operates in maximum power point tracking (MPPT) and low voltage ride through (LVRT) modes in normal grid and faulty grid condition modes, respectively. The proposed novel autonomous model predictive control (AMPC) scheme is leveraged to enhance the operation of the smart inverter. The AMPC includes online weight factor auto-tuning and control objective normalization to eliminate the required trial-and-error weight factor design stage in conventional model predictive control. This feature is particularly beneficial to the dual-mode smart inverter operation. The performance of the proposed grid-tied smart inverter based on the AMPC is verified experimentally. The results demonstrate that the proposed AMPC-based smart inverter features robust grid fault detection, autonomous adjustment of active and reactive power set-points, seamless transition between modes of operation, and elimination of controller tuning effort.

Megapixel time-gated SPAD image sensor for 2D and 3D imaging applications

We present a 1 Mpixel single-photon avalanche diode camera featuring 3.8 ns time gating and 24 kfps frame rate, fabricated in 180 nm CMOS image sensor technology. We designed two pixels with a pitch of 9.4 µm in 7 T and 5.75 T configurations respectively, achieving a maximum fill factor of 13.4%. The maximum photon detection probability is 27%, median dark count rate is 2.0 cps, variation in gating length is 120 ps, position skew is 410 ps, and rise/fall time is < 550 p s , all FWHM at 3.3 V excess bias. The sensor was used to capture 2D/3D scenes over 2 m with resolution (least significant bit) of 5.4 mm and precision better than 7.8 mm (rms). We demonstrate extended dynamic range in dual exposure operation mode and show spatially overlapped multi-object detection in single-photon time-gated time-of-flight experiments.

Dual-Mode FPGA-Based Triple-TDC With Real-Time Calibration and a Triple Modular Redundancy Scheme

This paper proposes a triple time-to-digital converter (TDC) for a field-programmable gate array (FPGA) platform with dual operation modes. First, the proposed triple-TDC employs the real-time calibration circuit followed by the traditional tapped delay line architecture to improve the environmental effect for the application of multiple TDCs. Second, the triple modular redundancy scheme is used to deal with the uncertainty in the FPGA device for improving the linearity for the application of a single TDC. The proposed triple-TDC is implemented in a Xilinx Virtex-5 FPGA platform and has a time resolution of 40 ps root mean square for multi-mode operation. Moreover, the ranges of differential nonlinearity and integral nonlinearity can be improved by 56 % and 37 % , respectively, for single-mode operation.

Modulation of Binary Neuroplasticity in a Heterojunction-Based Ambipolar Transistor.

To keep pace with the upcoming big-data era, the development of a device-level neuromorphic system with highly efficient computing paradigms is underway with numerous attempts. Synaptic transistors based on an all-solution processing method have received growing interest as building blocks for neuromorphic computing based on spikes. Here, we propose and experimentally demonstrated the dual operation mode in poly{2,2-(2,5-bis(2-octyldodecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithieno[3,2-b]thiophene-5,5-diyl-alt-thiophen-2,5-diyl}(PDPPBTT)/ZnO junction-based synaptic transistor from ambipolar charge-trapping mechanism to analog the spiking interfere with synaptic plasticity. The heterojunction formed by PDPPBTT and ZnO layers serves as the basis for hole-enhancement and electron-enhancement modes of the synaptic transistor. Distinctive synaptic responses of paired-pulse facilitation (PPF) and paired-pulse depression (PPD) were configured to achieve the training/recognition function for digit image patterns at the device-to-system level. The experimental results indicate the potential application of the ambipolar transistor in future neuromorphic intelligent systems.

A Dual-mode Communication Power Internet of Things Routing Algorithm Based on RPL Protocol

Medium frequency (less than 12 MHz) Power Line Communication (PLC) and micro-power wireless Radio Frequency (RF) communication dual-mode communication technology can realize the depth and breadth coverage of the power Internet of Things (IoT) and enhance the robustness of the network. But dual-mode communication also brings difficulties to the application of the RPL protocol. According to the characteristics of PLC and RF dual-mode communication technology, the routing communication delay is the optimization objective function, and a routing metric algorithm of RPL routing protocol is proposed. The RPL protocol is applied to the dual-mode communication in power Internet of Things. Experiments show that the proposed algorithm has higher communication efficiency and can meet the needs of dual-mode communication hybrid networking and operation. It is a feasible method.