Frequency Modulation Technique Research Articles

A new oversampling-based full-duplex radar jamming method with a single antenna

With the fast development of jamming technology, strong coherent jamming based on digital radio frequency memory (DRFM) technology poses serious threats to radar detection capabilities due to their flexibility and deception characteristics. However, the extremely high isolation between transmitter and receiver is difficult to implement in practice, and jammers typically operate in a transmit/receive time-sharing mode. Consequently, the duty cycle of jamming signal received by radar is less than 100% in the time domain, enabling the radar systems to detect targets amidst jamming. To generate a full duty cycle jamming signal, a new oversampling-based full-duplex DRFM jamming generation method is proposed in the transmit/receive time-sharing mode. This method requires that the intercepting width of jammer must be less than the reciprocal of value which is the product of forwarding times incremented by one and the radar signal bandwidth. Therefore, the jammer first intercepts extremely short segments from the radar signal using oversampling, with lengths measured in nanoseconds. Then, the jammer rapidly re-modulates and re-transmits the intercepted signal segments within the corresponding interception period. The jamming signal is filtered by the radar receiver. Then, the spectrum of the signal only contains the complete fundamental component, and the pulse width of the signal matches that of the transmitted signal, achieving a duty cycle of 100% and realizing the full-duplex jamming effect. In addition, the frequency modulation technique is utilized to generate dense false targets corresponding to the transmitted signal, thereby improving jamming efficiency. This paper elucidates the generation mechanism and ramifications of the jamming signal through rigorous signal analysis, delineating the relationship between intercepting length and full-duplex radar jamming generation across various DRFM jamming styles. Finally, the efficacy of full-duplex jamming is substantiated through theoretical analysis and simulation.

Sideband Vibro-Acoustics Suppression and Numerical Prediction of Permanent Magnet Synchronous Motor Based on Markov Chain Random Carrier Frequency Modulation

This paper presents a Markov chain random carrier frequency modulation (MRCFM) technique for suppressing sideband vibro-acoustic responses caused by discontinuous pulse-width modulation (DPWM) in permanent magnet synchronous motors (PMSMs) for new energy vehicles. Firstly, the spectral and order distributions of the sideband current harmonics and radial electromagnetic forces introduced by DPWM are characterized and identified. Then, the principle and implementation method of three-state Markov chain random number generation are proposed, and particle swarm optimization (PSO) algorithm is chosen to quickly find the key parameters of transition probability and random gain. A Simulink and JMAG multi-physics field co-simulation model is built to simulate and predict the suppression effect of the MRCFM method on the sideband vibro-acoustic response. Finally, a 12-slot-10-pole PMSM test platform is built for experimental testing. The results show that the sideband current harmonics and vibro-acoustic response are effectively suppressed after the optimization of Markov chain algorithm. The constructed multi-physics field co-simulation model can accurately predict the amplitude characteristics of the sideband current harmonics and vibro-acoustic response.

Ferromagnetic resonance measurement with frequency modulation down to 2 K.

Ferromagnetic resonance (FMR) spectroscopy is a powerful technique to study the precessional dynamics of magnetization in thin film heterostructures. It provides valuable information about the mechanisms of exchange bias, spin angular momentum transfer across interfaces, and excitation of magnons. A key desirable feature of FMR spectrometers is the capability to study magnetization dynamics over a wide phase space of temperature (T), frequency (f), and magnetic field (B). The design, fabrication, and testing of such a spectrometer, which uses frequency modulation techniques for improved detection of microwave absorption, reduces heat load in the cryostat and allows simultaneous measurements of inverse spin Hall effect (ISHE) induced dc voltages, is described in this paper. The apparatus is based on a 2-port transmitted microwave signal measurement using a grounded co-planar waveguide. The input radio frequency (RF) signal, frequency modulated at a tunable f-band, excites spin precession in the sample, and the attenuated RF signal is measured phase sensitively. The sample stage, inserted in the bore of a superconducting solenoid, allows magnetic field and temperature variability of 0 to ±5T and 2-310K, respectively. We demonstrate the working of this Cryo-FMR and ISHE spectrometer on thin films of Ni80Fe20 and Fe60Co20B20 over a wide T, B, and f phase space.

A Modified SVPWM Strategy for Reducing PWM Voltage Noise and Balancing Neutral Point Potential

PWM (pulse width modulation) is the most widely applied current conversion technology, but the high-frequency harmonics it causes have a significant negative impact on inverter system performance. This paper focuses on the three-phase T-type three-level inverter as the research object and addresses existing PWM voltage noise and midpoint potential imbalance issues by proposing an improved random SVPWM strategy, named Neutral Point Potential Balance Random Space Vector PWM (NPB–RSVPWM). The NPB–RSVPWM strategy includes three main steps: (1) introducing a midpoint potential balancing control loop to adjust the synthesis timing of the effective vectors to generate pulse signals, optimizing midpoint potential balance; (2) employing a randomly varying carrier frequency in place of the carrier used in the SVPWM strategy to generate the driving signals for switching devices; and (3) controlling the inverter through the driving pulse signals. This strategy optimizes the synthesis sequence of traditional SVPWM strategy vectors and incorporates random frequency modulation techniques. The mathematical model analyzes PWM harmonic expressions corresponding to fixed switching frequencies, and a random frequency carrier is chosen to suppress these PWM harmonics. The effective vector’s equivalent circuit is analyzed, proposing a technique for optimized vector synthesis timing. The simulation and experimental results verify that the NPB–RSVPWM technique can disperse PWM harmonic energy, reduce voltage noise, and optimize midpoint potential balance. Under the NPB–RSVPWM strategy, the line voltage spectrum becomes uniform, the maximum harmonic content is greatly reduced, and the fluctuation in the DC side midpoint potential is significantly improved. Compared with the traditional SVPWM strategy and random PWM strategy, the NPB–RSVPWM strategy has a lower voltage noise, smaller total harmonic distortion, and a more stable midpoint potential. The effectiveness and feasibility of the NPB–RSVPWM strategy are verified by simulation and experimental results.

Corrosion of Steel Rebars in Construction Materials with Reinforced Pervious Concrete

Pervious concrete has great potential for use in many practical applications as a part of urban facilities that can add value through water harvesting and mitigating severe damage from floods. The construction and agricultural industries can take direct advantage of pervious concrete’s characteristics when water is a key factor included in projects as part of the useful life of a facility. Pervious concrete also has applications in vertical constructions, fountains, and pedestrian crossings. This work evidences that pervious concrete’s corrosion current increases with increasing aggregate size. Also, corrosion is a factor to consider only when steel pieces are immersed, aggravated by the presence of chlorine, but it drains water and does not retain moisture. Steel-reinforced pervious concrete was studied, and the grain size of the inert material and the corrosion process parameters were investigated. The electrochemical frequency modulation technique is proposed as a suitable test for a fast, reproducible assessment which, without damaging reinforced cement structures, particularly pervious concrete, indicates a trend of increasing corrosion current density as the size of the aggregate increases or density diminishes.

A novel extendable multilevel inverter for efficient energy conversion with fewer power components: Configuration and experimental validation

SummaryMultilevel inverters (MLIs) are widely used in various sectors of power electronics. Some major benefits of using MLI are the high‐quality voltage output, harmonic reduction, and efficiency. However, MLIs also bear a range of disadvantages including an excessive number of components, high total standing voltage (TSV), and complicated control scheme. Thus, a novel cross‐switched neutral point clamped (CSNPC) nine‐level inverter is proposed. Many of the suggested MLIs use a large number of DC supplies and additional switches that are not fully utilized and generate high power loss. However, the proposed MLI topology has a smaller number of power electronic switches and DC supplies, leading to higher energy efficiency. Moreover, a simplified high frequency modulation technique, named hysteresis‐band‐based discontinuous pulse width modulation (DPWM) is devised to control the proposed MLI. This modulation scheme has effectively minimized capacitor voltage imbalance. Furthermore, the designed structure is extendable to a modular MLI, without any additional H‐bridge circuit. To verify its benefits over other recent similar types of MLIs, a thorough comparison is presented for the number of components and power losses. The proposed MLI has showed 95.54% efficiency, and the modular CSNPC can achieve a total harmonic distortion (THD) of 6.43%.

An Effective Modulation Technique for Multi Level Inverters

High frequency modulation techniques play very important role in multilevel inverters MLIs. These techniques have several advantages over low frequency modulation methods where they provide lower harmonic contents and higher performance in real time adaptation. Multicarrier sinusoidal pulse width modulation MCSPWM is a common high frequency technique and control method for MLIs. The synchronization of carrier signals, complexity of hardware components and high cost are very important issues when implementing multicarrier MCSPWM in real time. This paper presents an efficient approach that can overcome the problems of multicarrier signals. The proposed approach combines the advantages of low and high frequency modulation techniques. Real time adaptation of modulation index can be achieved easily, and harmonics contents are reduced to very low levels as well. Simulation and comparison of the proposed approach with MCSPWM are presented. The proposed approach is applied and tested effectively with different topologies of MLIs.

Two-wavelength digital holography using frequency-modulated continuous-wave technique for multiplexing in the time–frequency domain

Two-wavelength digital holography using frequency-modulated continuous-wave technique for multiplexing in the time–frequency domain

A Three-Level Resonant DAB Converter Featuring Minimized Circulating Losses for EV Battery Charging

A three-level modified series-parallel bidirectional isolated dc <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> dc resonant converter (TL-MSPBRC) is proposed for EV battery charging. The converter's performance is enhanced for wide load conditions as the modified series-parallel resonant tank is formed by considering the parasitics in the transformer. The first-harmonic approximation (FHA) equivalent circuit model is employed to analyze the converter characteristics for the frequency modulation technique. This converter has high conversion efficiency in charging and discharging operations because of the soft-switching capability of the power switches in the primary and secondary bridges. In addition, low on-state resistance switches in the three-level primary bridge minimize the conduction losses. A 3.3-kW converter prototype with a battery voltage range of 230 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 300-V is developed to validate the design method and the simulation results. The proposed converter has minimized circulating losses, good short-circuit protection, and excellent efficiency of 97.7% at the rated power level.

Development of QSAR based GFA predictive model for the effective design of a new bispyrazole derivative corrosion inhibitor

In this study, seven newly synthesized bispyrazole derivatives (PYR-1 to PYR-7) were investigated as corrosion inhibitors for 304 stainless steel (304 SS) in 1.0 M HCl solutions at different concentrations (10−13 to 10−5 M) using electrochemical frequency modulation technique (EFM). The experimental data were utilized to develop a predictive model for the anticorrosion abilities of bispyrazole ˗ based compounds. The model was developed by using the quantitative structure-activity relationship (QSAR) as a tool to relate essential molecular descriptors of bispyrazol with their experimental inhibition efficiencies. Chemical descriptors associated with frontier molecular orbitals (FMOs) were obtained using density Functional theory (DFT) calculations, while others were obtained from additional calculations performed using Material Studio 7 software. The suggested QSAR model was used to predict the corrosion inhibition efficiency of a newly synthesized bis[3‐(4`‐biphenyl)‐4‐[(4‐acetyl‐2‐(N‐phenylacetamido)‐4,5‐dihydro‐1,3,4‐thiadiazol‐5‐yl]‐1H‐pyrazol‐1‐yl]phosphineoxide,(PYR-8), another inhibitor within the same bispyrazole family. The predicted inhibition efficiency was validated by several electrochemical techniques. The predicted QSAR values for PYR-8 showed good agreement with experimental data, establishing the reliability of the model in predicting the inhibitor's performance.

SkinSense: Efficient vibration-based communications over human body using motion sensors

Recent growth in popularity of mobile and wearable devices has re-ignited the need for reliable and stealthy communication side-channels to enable applications such as secret/PIN sharing, co-location proofs and user authentication. Existing short-range wireless radio technology such as Bluetooth/BLE and NFC, although mature and robust, is prone to eavesdropping, jamming and/or interference, and is not very useful as a covert communication side-channel. This paper designs and implements SkinSense, a vibration-based communication protocol which uses human body/skin as a communication medium to create a low-bandwidth and covert communication channel between user-held mobile and wearable devices. SkinSense employs a novel frequency modulation technique for encoding bits as vibration pulses and a spectrogram-based approach to decode the sensed motion data (corresponding to the encoded vibration pulses) to reconstruct the transmitted bits. SkinSense is comprehensively evaluated for a variety of operational parameters, hardware setups and communication settings by means of data collected from human subject participants. Results from these empirical evaluations demonstrate that SkinSense is able to achieve a stable bandwidth of up to 6.6 bps, with bit error rates below 0.1 in our custom hardware setup, and can be employed as a practical communication side-channel.

A new generalized floor function based high switching frequency modulation and control technique: Multilevel inverters

SummaryA new generalized floor function (F2) based single carrier pulse width modulation (F2SC‐PWM) technique has been proposed in this paper by considering a single‐phase 9‐level T‐type packed U‐cell (PUC) inverter topology. In literature, the conventional level‐shifted PWM technique requires (level‐1) carriers, and the unipolar phase disposition (UPD) PWM technique requires (level‐1)/2 carriers to produce a particular level of output. To reduce the complexity of control, the authors have developed single‐carrier‐based PWM techniques. However, these are not generalized in a simple manner and are especially applicable only to particular inverter topologies. In this paper, a new F2SC‐PWM technique with a single modulating signal has been introduced that is applicable to any multilevel inverter (MLI) topology. This technique is very simple to implement, and it does not internally require any large number of mathematical operations and if‐else loops. Finally, a laboratory prototype has been used to verify the operation of the 9L‐TPUC topology considering R and RL loads with respect to step change of load, step change of modulation index (MI), and step change of modulation frequecy (MF) via with new proposed control technique (PCT).

Frequency modulation laser spectroscopy method for methane isotopologue ratio and total concentration measurements at 1661 nm

Source identification and accurate measurements of methane gas concentration are key tools necessary for climate change management. Here we present a method for methane isotopologue ratio measurement using a laser-based frequency modulation (FM) spectroscopy technique in the near infrared at 1661 nm. We provide line shape analysis and discuss a fitting algorithm for accurate isotopologue ratio metrology and investigate and minimize the effects of residual amplitude modulation on the experimentally produced FM signal line shape. This FM technique is further evaluated for future development of a cavity-enhanced and noise-immune system capable of isotopologue ratio as well as ultrasensitive trace gas measurements, all accessible using a single distributed feedback laser.

Improved Turn-On Speed of Low-Power Loads in Pulsed Power Supply Scheme and High-Energy Efficiency

There are cases in energy supply applications with low-power batteries, where the power required by the load is larger than the supply maximum deliverable power. Using a capacitor to create a high instantaneous power for the load was investigated as a useful solution. To increase the charging efficiency, a stepwise method for charging the capacitor was employed. This paper presents a new pulsed power supply approach in which the charging process is resumed after high instantaneous power delivery. Through this, the loss of residual energy in the capacitor was decreased and load turn-on speed and energy efficiency were significantly improved. The proposed structure consists of a buck converter that charges the capacitor using inductor current. A pulse frequency modulation (PFM) technique was used to generate the necessary signals for the buck converter switches, which resulted in controlling the inductor current. The proposed circuit was designed and simulated in a 0.18 [Formula: see text]m CMOS technology. It was shown that the designed CMOS circuit could reach a peak energy efficiency of 93.2% with a sleep period of 1.05 ms when the load consumes 7.06 [Formula: see text]J of energy.

A Burst Mode and Variable Frequency Voltage Sharing Control Mechanism for an Adjustable High Voltage Pulsed Converter

This article presents a modular adjustable high-voltage pulse (MAHVP) generation system. The proposed MAHVP generation system uses a combination of full-bridge LLC resonant converters whose input terminals are connected in parallel and whose output terminals are in series to boost the output voltage; input parallel output series configuration efficiently increases the power holding capabilities of the overall system. The MAHVP generation system uses a novel burst mode and variable frequency voltage sharing (BMVFVS) control mechanism, the BMVFVS control mechanism senses the type of load if the MAHVP generation system needs to operate at a heavy load, it uses the variable frequency voltage sharing method to divide the power equally between the modules to enhance the overall performance. For light load conditions, the MAHVP generation system operates in burst mode, and the BMVFVS control mechanism combined with the frequency modulation technique is used to control the amplitude and pulsewidth of the output voltage smoothly and efficiently. A hardware prototype of 2.4 kW is developed, and experimental results are taken to verify the feasibility and validity of the proposed system, the maximum output voltage of the developed two-module prototype is tested up to 6 kV at the high efficiency of 97%.

A Comparison of the Performance of Four Acoustic Modulation Techniques for Robot Communication in Pipes

Autonomous robotics is an emerging technology for the inspection of a vast network of underground pipes. Communication between autonomous robots is essential to optimise their efficiency and network coverage. However, sending a message acoustically is not a well-researched topic because most of the existing literature is devoted to the study of the acoustic properties of the pipe for the purpose of sensing rather than communication. In particular, the influence of multi-modal propagation and background noise on the quality of acoustic communication in pipes has not been well understood. This paper studies the performance of four standard acoustic communication techniques in a dry drainage pipe to fill this knowledge gap. The noise resistance, communication range and data rate of these techniques are estimated through numerical simulations and laboratory experiments. It has been found that the techniques based on shift keying requires at least 5--10 dB signal to noise ratio (SNR) to function properly while the chirp linear frequency modulation technique can operate reliably with SNR = 0 dB or event lower SNR. The results also suggest that the multi-modal propagation in the pipe has significant effects on the package error rate. The frequency dependent sound attenuation in the pipe also affects the communication range and data rate. In particular, for a 150 mm diameter dry pipe the maximum robot operation distance is likely to be limited to 50--100 m with the highest carrier frequency of around 10 kHz and data rates below 6300 bps. The results of this work pave the way to the development of acoustic communication modules to be deployed on tetheless robots designed to inspect a buried pipe network autonomously and collaboratively.

A dual-output switched-capacitor regulator with a self-controlled ripple reduction technique for self-powered EEG acquisition

In this paper, a novel dual-output switched-capacitor (SC) regulator is designed for EEG acquisition. At first, an efficient reconfigurable SC is designed with conversion ratios of 2/3 and 1/4 from 1.3 V input voltage. Reconfigurable SC with pulse frequency modulation (PFM) technique produces two single output voltages of 0.8 V and 0.2 V by changing the digital bit S. Then, a novel algorithm is proposed to produce two output voltages simultaneously and reduce voltage ripple. This SC regulator is self-controlled, and its control digital bits are entirely generated by the control logic circuit. Load current range is proportional to the EEG acquisition, in the range of 5 nA-1 μA and 500 nA-260 μA, for output voltages of 0.2 V and 0.8 V, respectively. The proposed dual-output SC is simulated in TSMC 65 nm CMOS technology and occupies an area of 2.09 mm2. The proposed SC regulator achieves a maximum power efficiency and output power of 92.8% and 193 μW, respectively.

Ray tracing of long-range underwater acoustic vortex wave propagation

The underwater acoustic communications environment is severely band-limited, which leads to a bottleneck in data transfer. Existing methods of data transfer in underwater acoustic communications applications typically rely primarily on conventional temporal and frequency modulation techniques and achieve bit rates peaking at approximately 40 kb/s. One method of easing the bottleneck and increasing the data rate is to explore further potential degrees of freedom which may be utilized. Acoustic orbital angular momentum (OAM) is a physical quantity that characterizes the rotation in a propagating helical pressure wavefront. The unique phase patterns of OAM carrying vortex waves form an orthogonal basis which may be useful as an additional degree of freedom in acoustics communications applications; however, the long-distance propagation of these waves is largely unstudied. By employing BELLHOP’s ray tracing algorithm, the dominant features of a propagating OAM carrying vortex wave are tracked over long ranges (to and beyond 1 km) under various environmental conditions. This provides essential guidance in the design of the sending and receiving arrays of high-speed underwater communications systems, which rely on multiplexing acoustic OAMs.

A High Efficiency Modified Forward Converter for Solar Photovoltaic Applications

In this paper, a modification of a conventional forward converter and a new mixed-stranded transformer winding technique are proposed for the development of a simple and high efficiency isolated dc-dc boost converter for solar photovoltaic applications. The conventional single switch forward converter topology is modified for simplification and elimination of losses due to the output filter components. A new mixed-stranded transformer winding technique is proposed to minimize the leakage inductance between the primary and tertiary windings for reducing losses. A pulse frequency modulation technique (PFM) is employed for reducing switching losses at low power operation. An experimental prototype of 300 W with a voltage step-up ratio of 1:12 has been built to obtain dc output voltage between 360-480 V for the dc input voltage of 30-40 V. Through the experimental results, it is shown that the converter can boost the input voltage according to the step-up ratio and exhibits a remarkably high dc-dc power conversion efficiency with a flat response curve. The average efficiency of around 95.5 % and peak efficiency of 97.6% are obtained.

Variable-Phase-Shift Based High Data Rate Sub-THz FSK Transmitter Design: Theory and Implementation

Targeting the new generation of high data rate communication systems at sub-terahertz (THz), a fully integrated, energy and area efficient, 196 GHz frequency-shift keying (FSK) transmitter was designed and prototyped in a 55-nm SiGe process. By analyzing the transient dynamics of a loop of coupled oscillators, a new direct modulation technique for frequency modulation is presented. It is shown that an instantaneous frequency shift can be realized in theory as long as the coupling mode of the coupled oscillators loop system does not change. By controlling the phase shift in a system of tunable couplers, a 10 Gb/s single channel data rate wireless link was demonstrated, which is the first FSK wireless transmitter at sub-THz frequencies, and is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times $ </tex-math></inline-formula> higher compared with all other previously published CMOS/BiCMOS wireless FSK transmitters. The achieved single channel data rate and energy efficiency per bit are comparable to other recently published sub-THz transmitters with more complicated modulation schemes like M-ary amplitude-shift keying (ASK), phase-shift keying (PSK), or quadratic-amplitude modulation (QAM).