Input Phase Research Articles

Design of compact rat-race couplers with enhanced bandwidth

This article presents a method to design compact rat race couplers with improved bandwidth values. The coupler consists of three coupled-line sections of different electrical lengths and characteristic impedances. First, design equations are obtained by imposing the coupler conditions using a lossless transmission line model. Input impedance matching, isolation, phase, and amplitude imbalances, all four conditions for both the sum and the difference port excitations are considered for bandwidth calculations. Then, an algorithm is developed to solve for the coupled-line parameters. Considering the limitations of fabrication, guidelines are provided for selecting the right physical parameters according to bandwidth requirement. As an example, a rat race coupler is fabricated that occupies 10% area of a conventional coupler without compromising the bandwidth values. Measurement results shows that the coupler provides 50% of 15 dB return loss bandwidth, 41.7% of 20 dB isolation bandwidth, 15% of ±5° phase imbalance bandwidth, and 62.5% of ±0.5 dB amplitude imbalance bandwidth which are more than those of a conventional 3λ/2 rat race coupler.

Weak-harmonic regularization for quantitative susceptibility mapping.

Background-field removal is a crucial preprocessing step for quantitative susceptibility mapping (QSM). Remnants from this step often contaminate the estimated local field, which in turn leads to erroneous tissue-susceptibility reconstructions. The present work aimed to mitigate this undesirable behavior with the development of a new approach that simultaneously decouples background contributions and local susceptibility sources on QSM inversion. Input phase data for QSM can be seen as a composite scalar field of local effects and residual background components. We developed a new weak-harmonic regularizer to constrain the latter and to separate the 2 components. The resulting optimization problem was solved with the alternating directions of multipliers method framework to achieve fast convergence. In addition, for convenience, a new alternating directions of multipliers method-based preconditioned nonlinear projection onto dipole fields solver was developed to enable initializations with wrapped-phase distributions. Weak-harmonic QSM, with and without nonlinear projection onto dipole fields preconditioning, was compared with the original (alternating directions of multipliers method-based) total variation QSM algorithm in phantom and in vivo experiments. Weak-harmonic QSM returned improved reconstructions regardless of the method used for background-field removal, although the proposed nonlinear projection onto dipole fields method often obtained better results. Streaking and shadowing artifacts were substantially suppressed, and residual background components were effectively removed. Weak-harmonic QSM with field preconditioning is a robust dipole inversion technique and has the potential to be extended as a single-step formulation for initialization with uncombined multi-echo data.

Three-dimensional light sculpting using a geometric analysis

Abstract Phase-only spatial light modulators (SLM) have been a staple in laser beam shaping research and applications due to their efficiency and programmability. An SLM’s capability to shape three-dimensional distributions of light has interesting applications in optical micromanipulation and microscopy. Since these SLMs operate by modifying the phase of incident light, it is common to model their operation using scalar diffraction theory or Fourier optics. In this work, we show how utilizing a ray tracing or geometric optics analysis can produce both interesting and practical results. We have previously shown how to generate laterally shaped beams that do not have the characteristic noise or discontinuities typical of the output generated with iteratively or numerically derived phase distributions. In this work, we extend the geometric approach to three dimensions to form interesting distributions that behave like non-diffracting beams, light sheets and beams that follow spiraling or diagonal paths as they propagate. The analytically derived input phase functions for these beams can be calculated in a straightforward manner. Hence, they are easily encoded and re-configured for SLM applications. Experiments demonstrate these 3D light distributions on a typical 2f holographic configuration, verifying its applicability on existing holographic setups.

A novel, tunable, multimodal microwave system for microwave reflectometry system.

Based on a new technique, a tunable, multi-channel system that covers the Q-band (33-55 GHz) is presented in this article. It has a potential use of the Doppler backscattering system diagnostic that can measure the turbulence radial correlation and the perpendicular velocity of turbulence by changing the incident angle. The system consists primarily of a double-sideband (DSB) modulation and a multiplier, which creates four probing frequencies. The probing frequency enables the simultaneous analysis of the density fluctuations and flows at four distinct radial regions in tokamak plasma. The amplitude of the probing frequency can be adjusted by the initial phase of the intermediate frequency (IF) input from the double-sideband, and the typical flatness is less than 10 dB. The system was tested in the lab with a rotating grating, and the results show that the system can operate in the frequency range of 33-55 GHz with a Q-band multitude and that the power of each channel can be adjusted by the phase of the IF input of DSB.

Ground current control scheme for back‐to‐back three‐phase T‐type rectifier and inverter systems

This paper presents a method to control the ground current in a back‐to‐back connection of three‐phase T‐type rectifier and inverter stages if operated from a three‐phase mains with a grounded neutral point and a star‐connected three‐phase load with grounded star point. The proposed control scheme requires a ground current sensor and a single control loop, achieves a closed‐loop control system bandwidth of 1.7 kHz, and does not interact with the existing input phase current control system that is used to achieve sinusoidal mains currents. According to the presented experimental results, an effective reduction of the rms ground current from more than 200 mA (without controller) to less than 3 mA (with the proposed control scheme) is realized. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Performance indicators for facilities operation and maintenance (Part 1)

PurposeThe purpose of this paper (Part 1 of 2) is to classify and map, in a systematic manner and from a facilities management (FM) perspective, the performance indicators that are applicable to evaluating facilities operation and maintenance (O&M) in commercial buildings.Design/methodology/approachForming part of a multi-stage research project, the applicable performance indicators that had been identified from an extensive literature review were consolidated and defined. Based on a phase-hierarchy (P-H) model – a fundamental classification framework comprising three phases of facilities services delivery and three hierarchical FM levels – the indicators were systematically classified, and a map showing their distribution along the phase and hierarchy dimensions was obtained.FindingsThe P-H model enabled systematic classification of the 71 applicable indicators. Mapping the indicators with the model showed that more indicators concern the input or output phase of facilities services delivery. Indicators at the strategic level, which have a wide span of control, are small in quantity, compared to the large number of indicators at the operational level.Research implicationsThe P-H model, which proves useful for classifying performance indicators for facilities in commercial buildings, may be applied to similar research on other types of buildings or infrastructures.Practical implicationsThe method of classifying the performance indicators and the mapping result of the indicators are useful reference for different levels of FM practitioners.Originality/valueThis paper illustrates a novel attempt that made use of the P-H model to classify O&M performance indicators.

Modular Transformer-Based Regenerative-Cascaded Multicell Converter for Drives With Multilevel Voltage Operation at Both Input and Output Sides

Cascaded multicell converter (CMC) is proved to be an effective solution for medium voltage drives. Three-phase diode bridge rectifiers are normally used in this converter, which do not have regeneration capability. Pulsewidth-modulated (PWM) rectifier-based power cells enable the drives with regeneration capability. However, due to their two-level voltage operation at the input side, an inductor is required for each cell to filter out the switching frequency components from the input current. In this paper, a new configuration with single-phase PWM rectifier-based power cell is proposed to achieve multilevel voltage operation at both the input and output sides of the converter. Therefore, the devices at the rectifier side are also operated at reduced switching frequency without using any filter inductor for each cell. In the proposed converter, simple modular transformers are used instead of a single large and complex transformer that is used in the conventional CMC. Further, input phase currents of the converter are controlled in the synchronously rotating d-q frame, which requires only two current sensors at the input side instead of individual current sensors for each cell. Experimental validation of the proposed converter configuration is carried out on a 4.5-kVA prototype, and the results are presented.

A novel scheme of cascaded four-wave mixing for phase-sensitive amplification in nonlinear optical fibre

We propose and numerically verify a scheme of phase-sensitive amplifier (PSA) using four-wave mixing (FWM) in cascaded highly nonlinear fibres (HNLFs), without requiring initial phase-locking between signal and pump. The first HNLF is used to generate two phase-conjugate waves, which act as two pumps for FWM process in second HNLF. We feed the two pumps from opposite ends of second HNLF and a signal co-propagating with one of the pumps. We keep the signal frequency in the middle of two pump frequencies to obtain phase-conjugate wave at the same frequency as the signal by FWM process in second HNLF. Signal and phase-conjugate wave appear at opposite ends of the second HNLF and combined to obtain PSA. The frequency-shift-free operation of phase conjugation helps in preserving the frequency of input signal during phase-sensitive amplification. We derive the expression for PSA signal output and PSA gain and show analytically that PSA gain depends upon signal phase only, as the two pumps are phase conjugate to each other. Thus, eliminating the need of phase locking between signal and pump waves. We show that PSA provides high gain for in-phase component and almost cancellation for quadrature-phase component of signal. We show the broadband nature of PSA due to minimum effect of group velocity and group velocity dispersion owing to counter-propagating nature of signal and conjugate waves. We study the performance of PSA under the effects of pump-signal detuning, amplifier length and input signal phase. Simulation results show that PSA output is forced to attain 0 or phase regardless of large variation of phase in the input signal. Nonlinear phase noise reduction of 100 Gbps DPSK signal transmitted over 1000-km standard single-mode fibre confirms phase regeneration by PSA.

Bilingual children’s story comprehension across language boundaries: does retelling improve comprehension?

ABSTRACT The main objective of this study was to investigate 9–10-year-old children’s comprehension processes during listening to and free recall of a story. A cross-linguistic design comprised texts in L1 German and recall in L2 English and vice versa. Corresponding mono-linguistic control conditions in either L1 or L2 allowed to examine the extent to which higher-level comprehension processes led to the same performance of story recall, construction of a coherent text representation and inference making across language boundaries. The findings revealed that comprehension predominantly occurred during the input phase. Better comprehension resulted when L1 input was provided as opposed to L2 input. Retelling the story in L1 added less to comprehension when the input was in L2. The findings supported the prediction derived from the capacity hypothesis that bilingual children’s comprehension benefits from resources set free by more automatic processing during listening to a story in L1. A comparable automaticity effect was not observed during retelling in L1. L1-dominant bilinguals’ comprehension reacted sensitively to bilingual language conditions in contrast to balanced bilinguals’ performance.

Generalised double line voltage synthesis strategy for three‐to‐ N phase matrix converter

This study proposes a generalised double line voltage synthesis strategy for 3 × N matrix converter. This strategy is simple without segment partitions and combinations, and it can be easily extended to any number of output phases. In order to gain the maximum VTR, the input line-to-line voltages and the `source key' are selected reasonably, according to the polarity of the input and output phase voltages which have maximum absolute value. The relationships between input and output voltages are obtained and the general expressions of duty ratios are derived. Further, input currents are analysed when input voltages are balanced or unbalanced. In addition, this study also proposes an innovative arrangement of switching sequence, which makes the relationship of duty ratios only one fixed case. This strategy reduces the complexity of control algorithm and inherits the advantage of traditional method. Desired output voltages are realised under both balanced and unbalanced input voltages. The feasibility and effectiveness of the proposed strategy are validated through the experimental results of 3 × 3 MC and 3 × 5 MC.

Reversible magnetic logic gates based on spin wave interference

We propose and develop reversible magnetic logic gates based on spin wave interference. The gates consist of passive elements including spin waveguides, cross-junctions, and phase shifters. Logic 0 and 1 are encoded in the phase of the propagating spin wave (0 or π). There are different possible input-output trajectories for the propagating spin waves, where some of the trajectories contain phase shifters and others do not. In each case, the particular input-output trajectory and the resultant output phase depend on the input phase combination. The redirection takes place in the cross junctions. Two waves coming to a junction in-phase propagate through the junction without reflection. In contrast, two waves coming to a junction out-of-phase are completely reflected back. The process of redirection is illustrated by numerical modeling of a nanometer-scale junction comprising two chains of spins, which operates at zero temperature. We also present experimental data on spin wave redirection in a micrometer-size cross junction made of Y3Fe2(FeO4)3 operating at room temperature. Our results demonstrate a prominent spin wave redirection, where the ratio of the transmitted power between the in-phase and out-of-phase cases exceeds 45 dB at room temperature. Based on these experimental data, we estimate the energy per operation in spin wave reversible logic circuits. The proposed reversible gates may provide a route to magnetic logic circuitry with power dissipation less than kT per operation.

Tracking past mining activity using trace metals, lead isotopes and compositional data analysis of a sediment core from Longemer Lake, Vosges Mountains, France

A 157-cm-long sediment core from Longemer Lake in the Vosges Mountains of France spans the past two millennia and was analyzed for trace metal content and lead isotope composition. Trace metal accumulation rates highlight three main input phases: Roman Times (cal. 100 BC–AD 400), the Middle Ages (cal. AD 1000–1500), and the twentieth century. Atmospheric contamination displays a pattern that is similar to that seen in peat bogs from the region, at least until the eighteenth century. Thereafter, the lake sediment record is more precise than peat records. Some regional mining activity, such as that in archaeologically identified eighteenth-century mining districts, was detected from the lead isotope composition of sediment samples. Compositional data analysis, using six trace metals (silver, arsenic, cadmium, copper, lead and zinc), enabled us to distinguish between background conditions, periods of mining, and of other anthropogenic trace metal emissions, such as the recent use of leaded gasoline.

Unity power factor three‐phase AC–DC converter applying two switch DCM SEPIC converter with coupled inductors

A two switch three-phase power factor correction SEPIC converter with coupled inductor operating in discontinuous current mode is presented. The switches voltage stress in this converter is related to peak of phase voltage instead of line voltage. Also, applying coupled inductor technique, not only reduces number of the magnetic cores but also with suitable design of coupling coefficient, input current ripple cancellation is achieved, so smaller inductor size can be used as input inductance. Thus, the proposed converter only applies three magnetic cores and <;5% THD is achieved with the proposed converter in a wide range of load and input voltage variations. Input phases are decoupled so converter can keep unity power factor even under unbalanced input source. Operating modes of the proposed converter is explained, and its input impedance is determined. It is verified that input impedance is pure resistive. The mathematical analysis and design procedure are discussed. Design example and experimental results from 400 W prototype with 220 V line to natural input RMS phase voltage and with 400 V output voltage operating at 40 kHz are presented to verify theoretical analysis.

Randomizing phase to remove acousto-optic device wiggle errors for high-resolution optical tweezers

Acousto-optic (AO) devices have been used extensively in optical tweezers because of their flexibility and speed; however, these devices have trap positioning inaccuracies that limit their usefulness, especially for high-resolution applications. We show that these inaccuracies are due to interference patterns within the AO device sound fields. We have devised a method that removes these inaccuracies by reducing the coherence of the sound fields by directly controlling and randomizing the phase of the radio frequency voltage input signal. We demonstrate that the trapping inaccuracies are eliminated, for both constant trap position and force-ramp measurements, and that no additional noise is added. We show that this random phase method is applicable to both acousto-optic modulator and deflector type devices and can be easily integrated via software upgrade into existing instruments.

Binocular vision adaptively suppresses delayed monocular signals

A neutral density filter placed before one eye will produce a dichoptic imbalance in luminance, which attenuates responses to visual stimuli and lags neural signals from retina to cortex in the filtered eye. When stimuli are presented to both the filtered and unfiltered eye (i.e., binocularly), neural responses show little attenuation and no lag compared with their baseline counterpart. This suggests that binocular visual mechanisms must suppress the attenuated and delayed input from the filtered eye; however, the mechanisms involved remain unclear. Here, we used a Steady-State Visual Evoked Potential (SSVEP) technique to measure neural responses to monocularly and binocularly presented stimuli while observers wore an ND filter in front of their dominant eye. These data were well-described by a binocular summation model, which received the sinusoidal contrast modulation of the stimulus as input. We incorporated the influence of the ND filter with an impulse response function, which adjusted the input magnitude and phase in a biophysically plausible manner. The model captured the increase in attenuation and lag of neural signals for stimuli presented to the filtered eye as a function of filter strength, while also generating the filter phase-invariant responses from binocular presentation for EEG and psychophysical data. These results clarify how binocular visual mechanisms—specifically interocular suppression—can suppress the delayed and attenuated signals from the filtered eye and maintain normal neural signals under imbalanced luminance conditions.

Analytic signal model for flip‐flop based phase‐frequency detectors

Flip-flop based phase-frequency detectors are widely used in phase-locked loop circuits. These devices are usually assumed to behave linearly although they consist of non-linear parts. In this work, a flip-flop based phase-frequency detector circuit is analysed. Analytic output signal models are derived for arbitrary input signal frequencies and phases. Exact and approximate closed-form solutions are found for different frequency ratios. The model is validated by numerical time-domain simulations.

An 8000-year multi-proxy peat-based palaeoclimate record from Newfoundland: Evidence of coherent changes in bog surface wetness and ocean circulation

Energy carried by warm tropical water, transported via the Atlantic Meridional Overturning Circulation (AMOC), plays a vital role in regulating the climate of regions bordering the North Atlantic Ocean. Previous phases of elevated freshwater input to areas of North Atlantic Deep Water (NADW) production in the early to mid-Holocene have been linked with slow-downs in the AMOC and changes in regional climate. Newfoundland’s proximity in the North Atlantic region to the confluence of the Gulf Stream and the Labrador Current and to an area of NADW production in the Labrador Sea makes it an ideal testing ground to investigate the influence of past fluctuations in ocean circulation on terrestrial ecosystems. We use multi-proxy peat-based records from the east coast of Newfoundland to derive a proxy-climate signal for the past 8000 years, which we have compared with changes in ocean circulation. Prominent shifts towards near-surface bog water-table levels, reflecting cooler/wetter climatic conditions, are evident in the early mid-Holocene at c. 7830, 7500, 7220 and 6600 cal. BP with minor changes occurring at c. 6340 and 6110 cal. BP. These events are coherent with evidence of meltwater injections into the N. Atlantic and of reduced NADW production. More recent increases in bog surface wetness in the mid- to late Holocene at c. 4290 and c. 2610 cal. BP are also consistent with reported periods of reduced NADW production. Coherence between the bog-derived palaeoclimate record developed from Newfoundland and evidence of fluctuations in ocean current strength is apparent in the early mid-Holocene.

Talasnost izlazne struje i dinamičke karakteristike osamnaestoimpulsnog tiristorskog ispravljača, projektovanog za napajanje elektromagneta

The aim of the paper is to analyse the possibility of applying a topology of an eighteen-pulse thyristor rectifier for the electromagnet power supply. The scope was to determine if the proposed rectifier topology, with the two input interphase transformers, as well as the output one, can work with an output current ripple being less than 100 ppm, with the acceptable dynamic characteristics of the voltage controller. Using the computer simulation, it has been found that, with a medium output filter capacitor and distinctively non-symmetric input parameters, the rectifier can work with an output current of approximately 80 ppm of the DC component. If the input phase voltages are equalized, the effective value of the output current ripple could be reduced down to 17 ppm. In both cases, satisfactory dynamic characteristics of the voltage controller have been achieved. The dominant influence on the output current filtering had the output interphase transformer magnetization inductance, as well as the capacitance of the filter capacitor. The increase of their values leads to better filtering of the output current, but also to a significant deterioration of the AC/DC converter dynamic characteristics. The measures for coordination of the output low-pass filter characteristics and the PI voltage regulator parameters are proposed.

Improving Grid Power Availability in Rural Telecom Exchanges

India has seen a huge surge in the telecom sector with total rural telecom subscribers doubling from 200.81 million to 404.16 million between 2010 and 2015. Therefore, telecom exchanges are built throughout the country to support this development. With severe electric power shortages in rural India, it poses a challenge to power these exchanges. It is observed that power supply in rural areas is not always available in three phase and can sometimes be available in two or single phase depending on fault in the three-phase system. Currently, used power plants in telecom exchanges are not designed to adapt to these variable input phase conditions. In this paper, a method is proposed to modify the currently used power plants such that they easily adapt to variable input phase conditions. This will lead to the utmost utilization of grid power and save valuable diesel fuel used in back-up diesel generators. The proposed method is designed and verified to have reasonable input power quality as per international standards. A quantitative estimation of diesel savings is also presented to estimate the percentage of diesel savings as a function of power outage.

Differential Phase Measurement Accuracy of a Monobit Receiver

Differential phase measurements using two receiver channels are used to calculate the angle of arrival of a target signal. A monobit receiver architecture is a desirable receiver type due to its low hardware complexity, sampling rate, and power efficiency. The application motivating this paper benefits from the use of automatic gain control circuitry and sensitivity offered by the monobit architecture. However, the one-bit sampling of the input signal introduces undesirable non-linear effects. This paper analyzes the effects of a monobit receiver architecture on the differential phase accuracy. Simulated results are compared to measurement data collected from prototype monobit receiver hardware. The measured data had good agreement with the simulated results. At a high-input signal-to-noise ratio of 30 dB, the differential phase measurement sigma was approximately 0.66° for input phase shifts of 0°, 45°, and 90°. While the differential phase measurement accuracy is less than predicted by the Cramer–Rao lower bound, it is sufficient for the low cost, power, and size constrained sensor application motivating this paper.