Continuous Frequency Modulation Research Articles

Frequency Regulation Adaptive Control Strategy of Wind Energy Storage System for Wind Speed Uncertainty

In order to reduce the negative influence of wind speed randomness and prediction error on frequency modulation, the reliability of the wind storage system was assessed effectively. In the wind storage frequency modulation system, a state of charge (SOC) adaptive adjustment method for wind speed randomness is proposed. Firstly, through the correlation analysis between the standby capacity of frequency modulation and the output power of wind turbine, the uncertainty of its frequency modulation capacity is revealed. Secondly, in view of the uncertainty of wind turbine frequency modulation, the output power of energy storage frequency modulation is optimized with the goal of minimizing the frequency modulation power deviation of the wind storage front under the framework of model predictive control, and the improved whale optimization algorithm (WOA) is used to solve the problem. Finally, the simulation results show that, under the given 5 min continuous disturbance, the root mean square of frequency regulation of the proposed restoration method is reduced by 56.65% compared to the SOC recovery base point set to 0.5. Under continuous large perturbations, the maximum frequency deviation is reduced by 0.0455 Hz. This effectively shows that this method can not only improve the frequency modulation reliability of wind power system but also improve the continuous frequency modulation capability of energy storage system.

Critical Design Considerations on Continuous Frequency Modulation Localization Systems

Real-time locating systems (RTLSs) suffer from clock synchronization inaccuracy among their distributed reference nodes. Conventional systems require periodic time synchronization and typically necessitate a two-way ranging (TWR) clock synchronization protocol to eliminate their measurement errors. Particularly, frequency-modulated continuous-wave (FMCW) time-based location systems pose unique design considerations on the TWR that have a significant impact on the quality of their measurements. In this paper, a valid operation design diagram is proposed for the case of an FMCW time-based TWR synchronization protocol. The proposed diagram represents an intersection area of two boundary curves that indicate the functionality of the system at a given frequency bandwidth, spectral length, and clock synchronization ambiguity. It presents an intuitive illustration of the measurement’s expected accuracy by indicating a larger intersection area for relaxed design conditions and vice versa. Furthermore, the absence of a working condition can easily be detected before proceeding with the actual system development. To demonstrate the feasibility of the proposed diagram, four scenarios with different design constraints were evaluated in a Monte-Carlo model of a basic TWR system. Moreover, an experimental measurement setup demonstrated the validity of the proposed diagram. Both the simulation and experimental outcomes show that the indicated valid conditions and the distribution of the measurements’ accuracy are in very good agreement.

Neural activity of retinal ganglion cells under continuous, dynamically-modulated high frequency electrical stimulation

Objective. Current retinal prosthetics are limited in their ability to precisely control firing patterns of functionally distinct retinal ganglion cell (RGC) types. The aim of this study was to characterise RGC responses to continuous, kilohertz-frequency-varying stimulation to assess its utility in controlling RGC activity. Approach. We used in vitro patch-clamp experiments to assess electrically-evoked ON and OFF RGC responses to frequency-varying pulse train sequences. In each sequence, the stimulation amplitude was kept constant while the stimulation frequency (0.5–10 kHz) was changed every 40 ms, in either a linearly increasing, linearly decreasing or randomised manner. The stimulation amplitude across sequences was increased from 10 to 300 µA. Main results. We found that continuous stimulation without rest periods caused complex and irreproducible stimulus-response relationships, primarily due to strong stimulus-induced response adaptation and influence of the preceding stimulus frequency on the response to a subsequent stimulus. In addition, ON and OFF populations showed different sensitivities to continuous, frequency-varying pulse trains, with OFF cells generally exhibiting more dependency on frequency changes within a sequence. Finally, the ability to maintain spiking behaviour to continuous stimulation in RGCs significantly reduced over longer stimulation durations irrespective of the frequency order. Significance. This study represents an important step in advancing and understanding the utility of continuous frequency modulation in controlling functionally distinct RGCs. Our results indicate that continuous, kHz-frequency-varying stimulation sequences provide very limited control of RGC firing patterns due to inter-dependency between adjacent frequencies and generally, different RGC types do not display different frequency preferences under such stimulation conditions. For future stimulation strategies using kHz frequencies, careful consideration must be given to design appropriate pauses in stimulation, stimulation frequency order and the length of continuous stimulation duration.

Wide range linearization calibration method for DFB Laser in FMCW LiDAR

In this paper, a solution based on a hybrid electro-optic phase-locked loop (HEO-PLL) is proposed to address the nonlinearity of the continuous sweep frequency of the light source in Frequency Modulated Continuous Wave (FMCW) LiDAR. This nonlinearity leads to large measurement errors, low accuracy, and poor system adaptability. The proposed solution uses a HEO-PLL to control the frequency sweep linearity of the distributed feedback (DFB) laser when it undergoes continuous, rapid, and wide-range frequency modulation through current tuning. The system is designed to allow the DFB laser to be used as a high-quality source for FMCW LiDAR. This enhances the resolution and ranging capability of the FMCW LiDAR with the DFB laser as the source, while avoiding issues such as difficult tuning of the loop bandwidth and central frequency and being highly susceptible to temperature and voltage variations caused by the charge pump phase-locked loop.

High-speed tunable microwave-rate soliton microcomb

Soliton microcombs are a promising new approach for photonic-based microwave signal synthesis. To date, however, the tuning rate has been limited in microcombs. Here, we demonstrate the first microwave-rate soliton microcomb whose repetition rate can be tuned at a high speed. By integrating an electro-optic modulation element into a lithium niobate comb microresonator, a modulation bandwidth up to 75 MHz and a continuous frequency modulation rate up to 5.0 × 1014 Hz/s are achieved, several orders-of-magnitude faster than existing microcomb technology. The device offers a significant bandwidth of up to tens of gigahertz for locking the repetition rate to an external microwave reference, enabling both direct injection locking and feedback locking to the comb resonator itself without involving external modulation. These features are especially useful for disciplining an optical voltage-controlled oscillator to a long-term reference and the demonstrated fast repetition rate control is expected to have a profound impact on all applications of frequency combs.

28-nm CMOS 공정을 이용한 고속 첩 신호 합성기 설계

This study proposes a frequency synthesizer with fast frequency modulation using a 28-nm CMOS process. The synthesizer used a two-point modulation technique that divides the frequency range into high- and low-pass regions to lock the frequency. In the high-pass region, continuous frequency modulation was achieved using a charge-digital-to-analog converter, while in the low-pass region, the synthesizer was set to the desired frequency using a divider and a delta-sigma modulator. The manufactured signal generator is capable of oscillating at frequencies between 14.1 GHz and 16.2 GHz, with a phase noise of −100.14 dBc/Hz at 1 MHz offset frequency. For chip signal generation, the generator had a chip time of 42.8 s and a bandwidth of 860 MHz. The chip area was 1,070×700 μm2.

Новый метод ладового мультифакторного анализа музыкальной формы для систематического музыковедения. Часть 1: Интервальное масштабирование и формообразующая роль градаций дыхания и музыкальной артикуляции

This article introduces a new method to analyze the tonal organization of music. This method uses “indefinite” intervallic typology instead of “definite.” The focus is on sounds with continuous frequency modulation and fluctuating pitch and time values rather than those with discrete time and frequency intervals that remain constant throughout a music work, forming sets of pitch and interval classes and rhythmic divisions. All existing methods of musicological analysis are primarily intended for the latter kind of music and are hardly useful for analyzing timbral rather than frequency characteristics of sounds and their relative registral position rather than “definite” pitch values. Our novel approach elaborates Eduard Alexeev’s theory of musical mode evolution, corroborating it with findings of modern psychoacoustics, biomusicology, ethology, evolutionary anthropology, genetic epistemology, and cognitive sciences. We implement the latest technologies for frequency and spectral analysis of music. Not only does our approach quantify the melodic, harmonic, rhythmic, metrical, thematic, and textural patterns of TO, but it also allows such aspects of musical expression as dynamics, tempo, articulation, breathing pulse, registration, and timbre to be evaluated. This multivariate method is supposed to improve considerably the analysis of music based on both “indefinite” and “definite” pitch forms. Such a comparative multifactorial analysis is essential for establishing the pathways of the global evolution of music and its biologically ingrained universalities and distinguishing music from other types of auditory communication. To summarize, we present the methodology for identifying the intervallic typology, articulatory gradations, and breathing segmentation of the music flow.

Optimization of laser stabilization via self-injection locking to a whispering-gallery-mode microresonator: experimental study.

Self-injection locking of a diode laser to a high-quality-factor microresonator is widely used for frequency stabilization and linewidth narrowing. We constructed several microresonator-based laser sources with measured instantaneous linewidths of 1 Hz and used them for investigation and implementation of the self-injection locking effect. We studied analytically and experimentally the dependence of the stabilization coefficient on tunable parameters such as locking phase and coupling rate. It was shown that precise control of the locking phase allows fine-tuning of the generated frequency from the stabilized laser diode. We also showed that it is possible for such laser sources to realize fast continuous and linear frequency modulation by injection current tuning inside the self-injection locking regime. We conceptually demonstrate coherent frequency-modulated continuous wave LIDAR over a distance of 10 km using such a microresonator-stabilized laser diode in the frequency-chirping regime and measure velocities as low as sub-micrometer per second in the unmodulated case. These results could be of interest to cutting-edge technology applications such as space debris monitoring and long-range object classification, high-resolution spectroscopy, and others.

Reliability improvement of wind power frequency modulation based on look‐ahead control strategy and stage of charge optimization of energy storage

Aiming at the continuous frequency modulation (FM) dynamic process of the current wind turbine (WT), FM reliability is affected by wind speed fluctuation and prediction error. This study proposes an advanced energy storage (ES) control strategy based on wind speed prediction. First, according to the wind speed fluctuation in a future forecast period, the model predictive control (MPC) method is used to modify the current charging and discharging behavior in advance to improve the FM reliability of WT in the forecast period. Second, considering the ES capacity limitation, an adaptive ES dynamic state of charge (SOC) two-layer optimization model is proposed. In the outer layer of the model, an optimization function is designed to automatically adjust the initial SOC value with the change in wind speed to maintain the optimal FM capability of the wind-storage system at different wind speeds. In the inner layer, the ES charge-discharge speed model is constructed to avoid the loss of ES life caused by overcharge and over-discharge in the continuous FM process. The simulation results show that in the continuous perturbation, maximum frequency deviation is improved by 0.035 Hz in the first perturbation and 0.036 Hz in the second perturbation compared with the non-optimization model. Besides, the deviation degree of system frequency decreased by 0.082 Hz under continuous load disturbance. The strategy and dynamic SOC optimization model can effectively improve the FM reliability.

Determination of Fast-Moving Objects’ Speed and Range with Linear Frequency Modulation Continuous Wave Radar Using Autocorrelation Scheme

Introduction. A hardware basis of modern Advanced Driver Assistance Systems (ADAS) consists of millimeterrange radars, characterized by a relatively short range (meters – tens of meters). At the same time, improving of traffic safety requires to increase the range at least to several hundred meters. The one way to achieve such values is to increase wavelength of a probing signal, to use the centimeter range of wavelengths, for example. The paper represents a detailed description of main steps of signal processing algorithm in the model of the ADAS low-power centimeter range radar, which provides fast-moving objects speed and range definition.Aim. Development of an algorithm for estimating the range and the speed of targets by an autocorrelation radar with a wide-band continuous linear frequency modulation (linear FM) signal in order to increase the rate of the ADAS system estimates formation.Materials and methods. The proposed algorithm is based on the methods of primary and secondary digital processing of radar signals. The model of a centimeter-range autocorrelation radar with a broadband continuous linear FM probing signal was used for practical researches. MATLAB software was used to process the received signal samples.Results. The algorithm has been developed to determine the speed and the range of fast-moving objects in conditions when their movement during the evaluation interval significantly exceeds the radar range resolution. The use of simplified Kalman filtering for inter-period secondary signal processing allowed to increase significantly the stability of the algorithm. In a full-scale experiment using the low-power radar model with continuous radiation of the centimeter range, it was shown that a stable assessment of a real car speed and range was provided at a distance of at least about one kilometer.Conclusion. The results of the field experiment make it possible to draw conclusions that the proposed algorithm is highly robust even in the absence of inter-period secondary processing. Its usage allows one to improve the stability of the algorithm without considerable additional computational costs. It is possible because near-linear dynamics of the observation object and of the radar carrier makes it sufficient to use a simplified implementation of Kalman filter in the form α-β-algorithm.

Enhancement of Range Resolution using Two Receivers in Continuous Time Frequency Modulation Technique

The resolution in range in continuous time frequency modulation (CTFM) is directly proportional to the pulse width of the compressed signal. The two receiver technique for continuous transmission frequency modulation processing was proposed as a technique to make resolution independent of the pulse width. In two receiver technique the output is without any discontinuity in time. Practically, it has been observed that the resolution in range is also limited by the pulse width of the probe signal bandwidth in the two receiver CTFM technique. The actual performance and limitation of the two receiver technique has been given in this paper.

ALGORITHM OF SIGNAL PROCESSING IN THE RADAR SYSTEM WITH CONTINUOUS FREQUENCY MODULATED RADIATION FOR DETECTION OF SMALL-SIZED AERIAL OBJECTS, ESTIMATION OF THEIR RANGE AND VELOCITY

Nowadays the interest in search of ways of improving the efficiency of small radar cross-section aerial objects detection and localization rises against the background of widespread use of light and unmanned aerial vehi-cles. As a result, researchers pay attention to radar systems (RS) with continuous linear frequency modulation (linear FM) signal. The use of such signals gives the measurable opportunity to reduce radar system peak-speech power and to cut the cost and weightsize parameters of the RS. The paper observes low-power ground based radar implementation prospects for purposes of detection and estimation of motion rates of small-sized aerial objects. The proposed algorithm of radar signals processing enables to simplify the detection of such tar-gets. The paper reveals the structure and defines the steps of the algorithm. The fundamental for the algorithm under consideration is the method of the range-Doppler image composition of the scanned area using digital signal processing. The paper presents the results of the algorithm operation in the low-power RS of C-band radar, obtained by processing of quadrotor echo-signals during the real experiment. The results show successful solvation of the applied problem of detection and tracking on the small-sized aerial object with the radar cross-section equal to less than 0.5 m2 and the spectrum of secondary radiation characterized by the expressed multimodality. The results of the experiment validate the application of the algorithm and demonstrate the possibility of the algorithm implementation in design of portable RS and automated target acquisition centers for detecting and tracking of the small-sized aerial targets (both, single as multi agent) with the information display on operator control panel.

An experiment of air-to-water sound propagation in deep water

The underwater sound propagation from an airborne source has been paid much attention recently. To explore the underwater sound propagation from an airborne source in deep water, an experiment was conducted in South China Sea. A vertical line array of hydrophones with depth from 100 meters to 3400 meters was anchored on the seabed to detect the sound of a loudspeaker. Two microphones were placed under the loudspeaker to measure the source level. Both continuous and linear frequency modulation wave signals with frequency from 100 Hz to 2000 Hz were transmitted by the loudspeaker. The distances between the loudspeaker and the vertical line array were from 5km to 14.5km. Comparing signal detected by underwater hydrophones with signal detected by microphones in air, transmission loss of is figured out. The transmission loss predicted by a wave number integration model OAST is compared with the experimental results.

Lindblad-Floquet description of finite-time quantum heat engines

The operation of autonomous finite-time quantum heat engines rely on the existence of a stable limit cycle in which the dynamics becomes periodic. The two main questions that naturally arise are therefore whether such a limit cycle will eventually be reached and, once it has, what is the state of the system within the limit cycle. In this paper we show that the application of Floquet's theory to Lindblad dynamics offers clear answers to both questions. By moving to a generalized rotating frame, we show that it is possible to identify a single object, the Floquet Liouvillian, which encompasses all operating properties of the engine. First, its spectrum dictates the convergence to a limit cycle. And second, the state within the limit cycle is precisely its zero eigenstate, therefore reducing the problem to that of determining the steady-state of a time-independent master equation. To illustrate the usefulness of this theory, we apply it to a harmonic oscillator subject to a time-periodic work protocol and time-periodic dissipation, an open-system generalization of the Ermakov-Lewis theory. The use of this theory to implement a finite-time Carnot engine subject to continuous frequency modulations is also discussed.

Autonomous radar pulse modulation classification using modulation components analysis

An autonomous method for recognizing radar pulse modulations based on modulation components analysis is introduced in this paper. Unlike the conventional automatic modulation classification methods which extract modulation features based on a list of known patterns, this proposed method classifies modulations by the existence of basic modulation components including continuous frequency modulations, discrete frequency codes and discrete phase codes in an autonomous way. A feasible way to realize this method is using the features of abrupt changes in the instantaneous frequency rate curve which derived by the short-term general representation of phase derivative. This method is suitable not only for the basic radar modulations but also for complicated and hybrid modulations. The theoretical result and two experiments demonstrate the effectiveness of the proposed method.

수산자원전용조사선 탐구 21호에 탑재된 최첨단 음향장비 소개와 첫 시험조사

At the first time in South Korea, the state of the art acoustic systems were mounted on the R/V Tamgu 21. The acoustic systems are an EK80 broadband echosounder (18, 38, 70, 120, 200 and 333 kHz) which has two beam modes such as continuous wave (narrowband) and frequency modulation (broadband), an ME70 multibeam echosounder (70-120 kHz), and a SH90 sonar (111.5-115.5 kHz). Acoustic data from broadband mode have a very short range resolution, a large detection range, a high signal to noise ratio, and a wide and consecutive frequency response. In ME70, each individual beam consisted in a multibeam plays a role as a spilt beam. The first trial of the cutting edge acoustic system installed on the R/V Tamgu 21 was conducted from 15 Feb to 29 Feb 2016 in East Sea, South Sea and East China Sea. The properties of the acoustic systems were elucidated and exploratory results from three systems were exhibited. Lastly, issues which should be considered and future research plan are mentioned.

Apoptotic cell death during Drosophila oogenesis is differentially increased by electromagnetic radiation depending on modulation, intensity and duration of exposure

Present generations are being repeatedly exposed to different types and doses of non-ionizing radiation (NIR) from wireless technologies (FM radio, TETRA and TV stations, GSM and UMTS phones/base stations, Wi-Fi networks, DECT phones). Although there is controversy on the published data regarding the non-thermal effects of NIR, studies have convincingly demonstrated bioeffects. Their results indicate that modulation, intensity, exposure duration and model system are important factors determining the biological response to irradiation. Attempting to address the dependence of NIR bioeffectiveness on these factors, apoptosis in the model biological system Drosophila melanogaster was studied under different exposure protocols. A signal generator was used operating alternatively under Continuous Wave (CW) or Frequency Modulation (FM) emission modes, at three power output values (10 dB, 0, −10 dB), under four carrier frequencies (100, 395, 682, 900 MHz). Newly emerged flies were exposed either acutely (6 min or 60 min on the 6th day), or repeatedly (6 min or 60 min daily for the first 6 days of their life). All exposure protocols resulted in an increase of apoptotic cell death (ACD) observed in egg chambers, even at very low electric field strengths. FM waves seem to have a stronger effect in ACD than continuous waves. Regarding intensity and temporal exposure pattern, EMF-biological tissue interaction is not linear in response. Intensity threshold for the induction of biological effects depends on frequency, modulation and temporal exposure pattern with unknown so far mechanisms. Given this complexity, translating such experimental data into possible human exposure guidelines is yet arbitrary.

Continuous Transmission Frequency Modulation Detection under Variable Sonar-Target Speed Conditions

As a ranging sensor, a continuous transmission frequency modulation (CTFM) sonar with its ability for range finding and range profile formation works effectively under stationary conditions. When a relative velocity exists between the target and the sonar, the echo signal is Doppler-shifted. This situation causes the output of the sensor to deviate from the actual target range, thus limiting its applications to stationary conditions only. This work presents an approach for correcting such a deviation. By analyzing the Doppler effect during the propagation process, the sensor output can be corrected by a Doppler factor. To obtain this factor, a conventional CTFM system is slightly modified by adding a single tone signal with a frequency that locates out-of-sweep range of the transmitted signal. The Doppler factor can be extracted from the echo. Both verification experiments and performance tests are carried out. Results indicate the validity of the proposed approach. Moreover, ranging precision under different processing setups is discussed. For adjacent multiple targets, the discrimination ability is influenced by displacement and velocity. A discrimination boundary is provided through an analysis.

Orthogonal Modes of Frequency Modulation and the Sturm–Liouville Frequency Modulation Model

Sinusoidal signals and complex exponentials play a critical role in LTI system theory in that they are eigenfunctions of the LTI convolution operator. While processing frequency-modulated (FM) waveforms using LTI systems, restrictive assumptions must be placed on the system so that a quasi-eigenfunction approximation holds. Upon deviation from these assumptions, FM waveforms incur significant distortion. In this paper, a Sturm-Liouville (S-L) model for frequency modulation introduced by the author, is extended to a) study orthogonal modes of continuous and discrete frequency modulation and b) to develop system theoretical underpinnings for FM waveforms. These FM modes have the same special connection with respect to the FM S-L system operator, that complex exponentials have with LTI systems and the convolution operator. The finite S-L-FM spectrum or transform that measures the strength of the orthogonal FM modes present in a FM signal, analogous to the discrete Fourier spectrum for sinusoids, is introduced. Finally, similarities between the orthogonal S-L-FM modes and angular Mathieu functions are exposed, and a conjecture connecting the two is put forth.

Transceiver for Human Body Communication Using Frequency Selective Digital Transmission

This paper presents a transceiver module for human body communications whereby a spread signal with a group of 64 Walsh codes is directly transferred through a human body at a chip rate of 32 Mcps. Frequency selective digital transmission moves the signal spectrum over 5 MHz without continuous frequency modulation and increases the immunity to induced interference by the processing gain. A simple receiver structure with no additional analog circuitry for the transmitter has been developed and has a sensitivity of 250 µVpp. The high sensitivity of the receiver makes it possible to communicate between mobile devices using a human body as the transmission medium. It enables half-duplex communication of 2 Mbps within an operating range of up to 170 cm between the ultra-mobile PCs held between fingertips of each hand with a packet error rate of lower than 10−6. The transceiver module consumes 59 mA with a 3.3 V power supply.