Quadrature Components Research Articles

Multi-Scale Induction Machine Model in the Phase Domain With Constant Inner Impedance

An efficient and accurate multi-scale induction machine model for simulating diverse transients in power systems is developed and validated. Voltages, currents, and flux linkages are described through analytic signals that consist of real in-phase and imaginary quadrature components, covering only positive frequencies of the Fourier spectrum. The stator is modeled in the abc phase coordinates of an arbitrary reference frame whose rotating speed is adjusted by a simulation parameter called shift frequency. When the reference frame is stationary at a zero shift frequency, then the model processes instantaneous signals to yield natural waveforms. When the reference frame is set to rotate at the synchronous frequency of the electric network, then the Fourier spectra of the analytic signals are shifted by this synchronous frequency to become dynamic phasors that allow for efficient envelope tracking. The shift frequency can be adapted during simulation. For any rotor position and independent of the variation of the magnetizing inductances with saturation, the induction machine model appears as a Norton current source with constant inner admittance in the abc phase domain to support the integration with simulators that represent the electric network in the abc phase domain. The analysis of test cases covering diverse transients substantiates the claims made in terms of accuracy and efficiency across different time scales.

FMCW Lidar Using Phase-Diversity Coherent Detection to Avoid Signal Aliasing

A frequency-modulated continuous-wave (FMCW) lidar is proposed to avoid signal aliasing in the measurement of distance and velocity. In the transmitter, a lightwave is amplitude-modulated in a Mach-Zehnder modulator by a linear-frequency modulated (LFM) waveform. The modulated light is used as a probe signal. The reflected optical signal beats with a local optical (LO) signal in a phase-diversity coherent optical receiver. The in-phase and quadrature components of the output signal are simultaneously recorded. The distance is extracted from the sum of the squares of the two components, while the velocity is calculated from the ratio of them. An experiment is carried out, in which the real-time distance and velocity of a spinning disk are measured. The proposed method can be used to solve the problems of signal aliasing which may lead to the ambiguity of distance and velocity measurements in traditional FMCW lidars. Moreover, the impacts of optical phase fluctuations are removed from the distance measurement in the proposed method.

Single-Phase Enhanced Phase-Locked Loops Based on Multiple Delayed Signal Cancellation Filters for Micro-Grid Applications

The grid voltage information such as the phase-angle, the frequency, and the amplitude is crucial for the design of synchronization and control of power converters in the micro-grid. The conventional approach to estimate the grid voltage information is accomplished by phase-locked loop (PLL) techniques. Among various existing PLL techniques, filter-based PLLs can provide more accurate estimations even under adverse grid conditions. In this paper, a new single-phase filtering technique based on multiple delayed signal cancellation (MDSC) is proposed for extracting both in-phase and quadrature components of the selected harmonic order of the single-phase grid voltage signal. This MDSC technique can be realized in both the direct-form and the recursive-form. In comparison with existing single-phase cascaded delayed signal cancellation (CDSC) techniques, this MDSC technique utilizes less memory for the extraction of grid voltage fundamental frequency component. The proposed MDSC filter can be applied as a pre-filter to the enhanced PLL (EPLL) for the prompt and accurate estimations of the grid voltage information under adverse grid conditions. Both frequency adaptive and non-adaptive MDSC-based EPLL schemes are proposed in this paper. To validate the effectiveness of the proposed methods, experiments are conducted on the MDSC-based EPLLs and compared with the CDSC-EPLL under various grid voltage disturbances.

An Improved Sensorless DTC Technique for Two/Three-Level Inverter Fed Asynchronous Motor

The Direct Torque Control (DTC) technique was designed to provide high performance for a three-phase asynchronous motor’s behavior by accurately controlling the flux and torque of the latter. However, this conventional DTC generates strong ripples at the level of flux and torque and a variation of the switching frequency since it uses hysteresis comparators, for this reason, the sine-triangle pulse width modulation (SPWM) has been proposed to improve it. The use of Integral Proportional Regulators (PI) allows the generation of the voltage direct and quadrature components that serve as inputs for the SPWM. The technique thus presented provides a fixed switching frequency and lower undulations at the torque and the stator flux. The objective of this work is to apply the improved DTC technique for the control of a cage asynchronous motor that will be powered by two inverters of different topologies; the first is the two-level and the second is the three-level of Neutral point clamped NPC structure. In addition, the control strategy uses a speed estimator that allows the elimination of the mechanical sensor, which greatly increases the reliability of the system. To evaluate the performance and efficiency of the proposed method, a simulation using the MATLAB / SIMULINK software and a fair comparison between the results of the two inverters will be made.

The Rician Complex Envelope Under Line of Sight Shadowing

This letter investigates a Rician complex envelope which is subject to line-of-sight (LOS) shadowing. In particular, exact closed-form expressions are obtained for the joint envelope-phase distribution, the distribution of the phase, and that of the quadrature and in-phase signal components. Using the new formulation for the phase distribution, we find that for increasing shadowing severity, the phase becomes progressively more disperse. Interestingly, the phase is shown to be unimodal. This illustrates that the relationship which is known to exist between the envelope of Rician fading which undergoes LOS shadowing and Hoyt fading does not extend to the phase. We also provide two applications of our new results which investigate the average bit error probability and the average symbol error probability for phase-based modulation schemes operating in LOS shadowed fading channels. The results are shown to provide excellent agreement with Monte Carlo simulations.

Grid-Tied Inverter With AC Voltage Sensorless Synchronization and Soft Start

This paper presents a novel grid synchronization method with bumpless start that requires minimal computational load and can selectively track the positive sequence of the grid voltage in an unbalanced and distorted three-phase weak grid. Only 12 floating-point operations are required to obtain the in-phase and quadrature components that define a synchronous frame which tracks the positive sequence of the grid voltage. Contrary to a phase-locked loop (PLL), the presented scheme does not require to measure any ac voltages. Therefore, this sensorless method is particularly suited for weak-grid conditions, in which the voltage at the point of common coupling may contain significant noise and can experience larger deviations from the grid voltage (compared to a strong grid) due to the voltage drop in the weak grid impedance. The error in the estimated phase depends on the accuracy of the plant model. If the LCL filter parameters are known, then both the proposal and a PLL-based scheme result in the same steady-state error. Experimental results show the advantages of the proposal compared to a moving average filter PLL.

Ultra-Low Complex Blind I/Q-Imbalance Compensation

Direct-conversion transceivers are the predominating architecture in current mobile communication systems. Despite many advantages, this topology suffers from unavoidable mismatches in the analog part, which causes imbalance between the in-phase and quadrature (I/Q) component. In this paper, we present a novel fully digital, blind I/Q imbalance compensation algorithm that features extremely low computational complexity and high compensation performance for a wide range of input signal types. Different to many state-of-the-art compensation schemes, the approach is not based on a gradient descent optimization and does not require any global feedback. This simplifies the implementation at high data rates and reduces the configuration effort to a minimum. For comparison, we examine an existing method of moment-based estimator with similar properties, for which we also provide the detailed insights beyond available literature. For both algorithms, we provide a rigorous mathematical analysis, which is supported by simulations with a focus on various long-term evolution (LTE) signal types. In addition, hardware architectures, including field-programmable gate array (FPGA) verification, are presented for both algorithms.

Metal Discrimination in Metal Detector

In the article show the basic principles of metal detection, proposed methods for measuring the quantities by which the type of metal can be determined, and methods for improving the accuracy of metal detection and classification. A hardware implementation of a data processing and analysis unit for determining the type of metal has been developed. Digital data processing tools were used for the implementation, which allows to simplify the block design, minimize possible errors and noises during measurement, distorting the final result of the detection and classification of metals.In the modern world people has to deal with a large number of different metals. There is a problem of distinguishing one type of metal from all others. Such a function of metal detectors is called discrimination. Metal Detector Discrimination is a function that allows you to recognize marked objects by metal type and classify them. Modern high-precision metal detectors contain a large number of functional blocks, complex in setting up and use, sensitive to noise and errors during measurement and detecting metal. The task is to design a unit for discrimination of metals that would consist of a minimum number of functional units, required minimum number of settings and could give correct information about the presence of metal and type of metal and will be insensitive to disturbances caused by the noise and errors during measurement.Metal detectors operate on the principle of magnetic field generation and analysis of the feedback signal from a metal object and the environment. The transmitted magnetic field varies in time. The transmitter is made as coil with an electric current of a certain shape, passing through it and obtained from the generator block. The receiver is made as receiving coil connected to the amplification, filtering and processing unit of the received signal. Any metal has the properties of the resistivity and the properties of the inductance. Using information about the phase difference and amplitude between transmitted and received signals, we can determine type of the metal. To find the phase and amplitude of the received signal, the signal from the metal can be divided into two components: quadrature component has the same form of signal as the transmission signal, but is shifted in time relative to the transmitted signal (phase difference); in-phase component has the same form of signal as the signal transmitted, but, the amplitude of the received signal changes. Then using this two components find the phase and amplitude of the signal. To increase accuracy of the measurement using “ground balancing” principals, and ferrite calibration. As a result get the block for metal discrimination with simple design, minimum number of setting and good capabilities to minimize noise and errors during measurement.Ref. 12, fig. 8.

A new SOGI-PLL method based on fuzzy logic for grid connected PV inverter

<p>Phase angle detection of the grid voltage is an imperative part of control in most applications, especially for the synchronization of the current injected by the grid-connected photovoltaic inverters. Consequently, fast and accurate detection of the phase angle, frequency and amplitude of the grid voltage are indispensable data to ensure a correct generation of reference signals and operation of the grid connected inverters. We present in this work a new phase-locked loop (PLL) method for single-phase systems. The novelty is to generate an orthogonal voltage system using a second-order generalized integrator (SOGI), followed by a Park transformation, whose quadrature component is forced to zero by the fuzzy logic, in order to obtain rapid detection and a more accurate picture of the phase angle. Furthermore, simulation results with PSIM software will be submitted to verify the performance and effectiveness of the proposed method strategy. Finally, the experimental test will be used to extract the result and discuss the validity of the proposed algorithm.</p><p> </p>

Comprehensive Performance Evaluation of Computationally Efficient Discrete Fourier Transforms for Frequency Estimation

In this paper, the design of frequency-locked loop (FLL) is proposed based on computationally efficient discrete Fourier transform (DFT) structures. In recent years, the DFT structures are evolved as sliding DFT (SDFT), modulated SDFT, hopping DFT (HDFT), modulated HDFT, and sliding-windowed infinite Fourier transform. Considering their tuned filter characteristics, an attempt has been made to obtain a solution for the instantaneous frequency estimation problem of the input signal under varying center frequency condition. In each DFT structure, the $k$ th bin in-phase and quadrature components are separated for instantaneous signal extraction. The feedback loop is designed around these DFT structures, and it was observed that the frequency responses exhibit flat magnitude and phase interestingly when compared with the open-loop structures. Hence, an adaptive sampling frequency adjustment scheme is proposed for these structures as FLL to estimate the instantaneous frequency of the input signal for the wide variation in center frequency. These FLLs with different DFT structures are tested for dynamic performance and wide operating range. The proposed FLLs are implemented in field-programmable gate array (FPGA), and the experimental investigations have been carried out for frequency estimation. Further experimental investigations on these FLLs as a system on chip were carried out with area and power analysis.

Performance of model predictive control approach for single‐phase distributed energy grid integration with PQ control

This study investigates the performance of finite control set–model predictive control (FCS–MPC) strategy employed for the control of active (P) and reactive power (Q) injected to the grid from a distributed energy resource using a single-phase grid-tied inverter. In the study, three different computational methods are utilised to create the orthogonal components of grid current and voltage in the stationary reference frame that are required for PQ computations. The obtained results indicate that FCS–MPC approach is effective to provide flexible control of the power injected to the grid. Moreover, the steady state and transient performance of P and Q components are affected by the method of creating the imaginary quadrature component. Owing to the results, the second-order generalised integrator method provides the best steady state performance in terms of the lowest total harmonic distortion of grid current and minimum resultant peak–peak power ripple. While the quarter cycle phase delay method results in the worst transient behaviour owing to an unavoidable time delay of 0.005 s in case of 50 Hz supply system. In addition, the robustness of the FCS–MPC system is examined against parameters variation over a wide range. The overall FCS–MPC system is studied using PSIM® software.

Merged Cloud and Precipitation Dataset from the HIAPER GV for the Cloud System Evolution in the Trades (CSET) Campaign

AbstractThe Cloud System Evolution in the Trades (CSET) aircraft campaign was conducted in the summer of 2015 in the northeast Pacific to observe the transition from stratocumulus to cumulus cloud regime. Fourteen transects were made between Sacramento, California, and Kona, Hawaii, using the NCAR’s High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Gulfstream V (GV) aircraft. The HIAPER W-band Doppler cloud radar (HCR) and the high-spectral-resolution lidar (HSRL), in their first deployment together on board the GV, provided crucial cloud and precipitation observations. The HCR recorded the raw in-phase (I) and quadrature (Q) components of the digitized signal, from which the Doppler spectra and its first three moments were calculated. HCR/HSRL data were merged to develop a hydrometeor mask on a uniform georeferenced grid of 2-Hz temporal and 20-m vertical resolutions. The hydrometeors are classified as cloud or precipitation using a simple fuzzy logic technique based on the HCR mean Doppler velocity, HSRL backscatter, and the ratio of HCR reflectivity to HSRL backscatter. This is primarily applied during zenith-pointing conditions under which the lidar can detect the cloud base and the radar is more sensitive to clouds. The microphysical properties of below-cloud drizzle and optically thin clouds were retrieved using the HCR reflectivity, HSRL backscatter, and the HCR Doppler spectrum width after it is corrected for the aircraft speed. These indicate that as the boundary layers deepen and cloud-top heights increase toward the equator, both the cloud and rain fractions decrease.

Extraction of Carrier Phase Delay for Nonlinear Errors Compensation of PGC Demodulation in an SPM Interferometer

Traditional phase generated carrier (PGC) schemes require that the carrier phase delay be kept zero and the phase modulation depth be maintained at a certain value; otherwise, serious nonlinear errors will be introduced into the phase demodulation of a sinusoidal phase modulation interferometer. Proposed herein is a robust carrier phase delay extraction method for nonlinear errors compensation of PGC demodulation that mitigates the effect of the interference phase shift. The carrier phase delay is directly extracted by adopting the first-, second-, and fourth-order in-phase and quadrature harmonic components generated by quadrature multi-harmonics frequency down conversion. Further, with the extracted phase delay, real-time compensations for the phase delay and phase demodulation depth are realized simultaneously in PGC demodulation. Theoretical analysis and derivation of the proposed method are given in detail. Simulation and displacement measurement experiments with different phase delays and phase modulation depths are performed to verify the effectiveness of the proposed method. The experimental results demonstrate that the proposed method is able to precisely extract the phase delay and efficiently eliminate the effects of the phase delay and modulation depth instability.

SYNTHESIS OF TWO-POINT PARTIALLY COHERENT MODEL, PROVIDING SPECIFIED CORRELATION CHARACTERISTICS OF ANGULAR NOISE, BASED ON ITS EQUIVALENCE OF THREE-POINT NON-COHERENT MODEL WITH SEPARABILITY OF SPATIAL AND TEMPORAL COORDINATES

The paper considers approaches developed for the synthesis of a two-point geometric model that emits correlated signals and forms angular noise with given spectral-correlation properties, based on its equivalence of a three-point model that emits noncorrelated signals. Analytical relationships have been obtained that allow us to determine the spectral correlation characteristics of the signals supplied to the emitters of the two-point partially coherent model. The basis for the synthesis of a two-point model, emitting correlated signals, is a three-point model, emitting non-correlated signals. The considered models can replace a one-dimensional object that has the property of separating the spatial and temporal variables in functions that determine the distribution of the density of the auto- and cross-correlation quadrature components of the echo signal over the object. In this case, all points of the object being replaced reflect echoes with the same spectral and correlation properties. The obtained theoretical results are confirmed by digital modeling. The obtained probability density distributions of the angular noise and their correlation functions coincide for the two considered models.

Sensing and tracking enhanced by quantum squeezing

Quantum sensing, along with quantum communications and quantum computing, is commonly considered as the most important application of quantum optics. Among the quantum-sensing experiments, schemes based on squeezed states of light are popular choices due to their natural quadrature components. Since the first experimental demonstration of quantum-squeezing-enhanced phase measurement beyond the shot-noise limit in 1987, quantum-squeezing techniques toward practical sensing and tracking have been extensively investigated. In this paper, we briefly review the recent developments of quantum squeezing and its applications in several advanced systems for measurements of position, rotation, dynamic motion, magnetic fields, and gravitational waves. We also introduce the recent experimental efforts to combine the quantum-squeezing lights into fiber sensing systems.

Enhanced Multiuser Superposition Transmission Through Structured Modulation

The fifth-generation (5G) air interface, namely, dynamic multiple access (MA) based on multiuser superposition transmission (MUST) and orthogonal MA (OMA), may require a complicated scheduling and heavy signaling overhead. To address these challenges, we propose a unified MA scheme for future cellular networks, which we refer to as structured MUST (S-MUST). In S-MUST, we apply complex power allocation coefficients (CPACs) over multiuser legacy constellations to generate a composite constellation. In particular, the in-phase ( $I$ ) and quadrature ( $Q$ ) components of the legacy constellation of each user are separately multiplied by those of the CPACs. As such, the CPACs offer an extra degree of freedom for multiplexing users and guarantee fairness in symmetric broadcast channels. This new paradigm of superposition coding allows us to design $IQ$ separation at the user side, which significantly reduces the decoding complexity without degrading performance. Hence, it supports low-complexity frequency-selective scheduling that does not entail dynamical switching between MUST and OMA. We further propose to quantize the CPACs into complex numbers where $I$ and $Q$ components of each quantized coefficient are primes, facilitating parallel interference cancellation at each user via modulo operations; last but not least, we generalize the design of S-MUST to exploit the capabilities of multiantenna base stations. The proposed S-MUST exhibits an improved user fairness with respect to conventional MUST (134% spectral efficiency enhancement) and a lower system complexity compared with dynamically alternating MUST and OMA.

QUADRATURE COMPONENTS FORMING METHOD FOR HOMODYNE ACOUSTO-OPTIC SPECTRUM ANALYZER

Introduction. Among acousto-optic spectrum analyzers with spatial integration, schemes based on optical interferometers provide the largest dynamic range. Nevertheless, they form the signal amplitude spectrum on a certain spatial carrier. Formation of quadrature components can eliminate this spatial carrier. The two-dimensionality of the transformations performed in optical processors provides this elimination by reading of the additional charge of matrix photosensor lines. A renowned method implements this approach using four lines, which in turn determines the estimation time of the signal spectrum.Objective. The objective of the work is to study the possibility of time reduction of the spectrum estimation.Materials and methods. The paper presents the description of two methods of forming the necessary components.The first method uses three photosensor lines, the charge distribution in which has the spatial carrier phaseshifted by 90 ° from line to line. The second method forms the necessary distributions sequentially in three accumulation cycles by means of variation of the initial phase of the reference signal. By the mathematical proof, three distributions with a 90 ° relative phase shift are sufficient to eliminate the spatial carrier.Results. In the first method, reduction of the spectrum estimation time is insignificant, but the parallel distributions formation affords not to impose additional requirements on the signal spectrum. The second method, due to the possibility of using any three sequentially formed distributions for estimation, is potentially three times faster than the first method, but requires the stationary signal spectrum within three accumulation cycles. Researchers can implement this meth-od using a linear photosensor or TDI photosenor. In addition, the method is less demanding to optical scheme parameters.Conclusion. The proposed quadrature components formation methods provide time reduction of the spectrum estimation in interference acousto-optic spectrum analyzers and simplify their design.

Probability Distribution of Intercore Crosstalk in Weakly Coupled MCFs With Multiple Interferers

The statistical behavior of the intercore crosstalk (ICXT) power in weakly coupled multicore fibers (MCFs) with multiple interfering cores is experimentally assessed. The histograms with multiple interfering cores are compared with the probability density function (pdf) of the quadratic form corresponding to the ICXT power considering different correlation coefficients between the in-phase and quadrature Gaussian ICXT field components of the orthogonal polarizations. A very good fitting between experimental histograms and the numerical pdf of the quadratic form occurs when the ICXT field components are modeled as uncorrelated random processes. These results demonstrate that the ICXT power can, with a very low error, be described by a chi-square distribution with 4 degrees of freedom not only with a single interfering core but also with multiple interfering cores. This means that the ICXT contributions induced by different cores of the MCF are uncorrelated.

New Saddle-Point Technique for Non-Coherent Radar Detection With Application to Correlated Targets in Uncorrelated Clutter Speckle

This paper presents a novel implementation of the saddle-point technique for calculating the non-coherent detection probability of targets by airborne surveillance radar in the presence of pulse-to-pulse correlation. It is based on the inverse Laplace transform of the moment generating function for the returned power distribution by means of integration along the path of steepest descent. To illustrate the methodology, the problem of non-coherent pulse integration for a target with gamma-fluctuating partially correlated radar cross-section embedded within compound surface clutter with uncorrelated speckle is revisited. This situation arises for maritime or overland surveillance radar with sufficient frequency agility to fully decorrelate the clutter speckle but not the fluctuations of the target radar cross-section. An exact method and a hierarchy of approximations are described, all of which perform well for this problem. Monte Carlo simulation at the quadrature component level is used to verify the results.

Hand-Gesture Recognition Using Two-Antenna Doppler Radar With Deep Convolutional Neural Networks

Low-cost consumer radar integrated circuits combined with recent advances in machine learning have opened up a range of new possibilities in smart sensing. In this paper, we use a miniature radar sensor to capture Doppler signatures of 14 different hand gestures and train a deep convolutional neural network (DCNN) to classify these captured gestures. We utilize two receiving antennas of a continuous-wave Doppler radar capable of producing the in-phase and quadrature components of the beat signals. We map these two beat signals into three input channels of a DCNN as two spectrograms and an angle of arrival matrix. The classification results of the proposed architecture show a gesture classification accuracy exceeding 95% and a very low confusion between different gestures. This is almost 10% improvement over the single-channel Doppler methods reported in the literature.