Conventional Modulation Research Articles

OTFS Waveform Based on 3-D Signal Constellation for Time-Variant Channels

Orthogonal time frequency space (OTFS) is a new waveform modulated in the delay-Doppler domain that can achieve better communication performance than the conventional waveform, such as orthogonal frequency division multiplexing (OFDM), in high-mobility scenarios. In this letter, we introduce the three-dimensional (3-D) mapper into the conventional OTFS modulation scheme to further reduce the bit error rate (BER) at higher modulation orders. Moreover, the minimum Euclidean distance of the 3-D signal constellations and detector complexity analysis of the proposed 3D-OTFS are presented. The simulation results demonstrate that the proposed 3D-OTFS system outperforms the conventional OTFS system in terms of BER performance for higher modulation orders in time-variant channels, such as the Extended Vehicular A (EVA) channel and the Extended Pedestrian A (EPA) channel. Furthermore, performance comparisons between the proposed 3D-OTFS and 3D-OFDM in different time-variant channels show that the proposed 3D-OTFS is better suited for high-mobility communication scenarios.

Multiaverage Random Switching Frequency Space Vector Pulsewidth Modulation Strategy for High-Order Harmonics Dispersion

A multi-average random switching frequency space vector pulse width modulation (MARSF-SVPWM) strategy is proposed in this paper, in order to further disperse the high-order harmonics concentrated at the switching frequency and its integer multiplies in the output voltage of the inverter. The proposed strategy divides the fundamental period equally, with different stages corresponding to different average switching frequencies and spread-spectrum ranges, in contrast with the conventional random switching frequency space vector pulse width modulation (RSF-SVPWM), under the premise of maintaining the same overall average switching frequency and spread-spectrum range. The simulation and experimental results demonstrate that, even in the case of a narrow spread-spectrum range, the proposed MARSF-SVPWM strategy can obtain a better effect of high-order harmonic dispersion.

Single-sideband Suppressed-carrier Modulation and Demodulation: Principles, Analysis, Circuits, and Applications

This comprehensive article provides an in-depth exploration of single-sideband (SSB) modulation and demodulation techniques. The article discusses the principles, fundamental methods, and circuits involved in SSB modulation, highlighting its efficiency as an analog amplitude modulation method for long-distance information transmission while effectively utilizing available bandwidth. A comparative analysis of various modulation methods, including conventional amplitude modulation, double-sideband (DSB)modulation, vestigial sideband (VSB) modulation, frequency modulation (FM), phase modulation (PM), and single-sideband (SSB) modulation, is presented. Furthermore, the article delves into the diverse applications of SSB analog amplitude modulation.

A nonbinary LDPC-coded product distribution matching probabilistic shaping scheme for high order modulation

In this paper, a non-binary low-density parity-check (LDPC)-coded low complexity product distribution matching (PDM) probabilistic shaping (PS) scheme for high-order modulation is proposed. Compared with conventional non-binary LDPC-coded regular quadrature amplitude modulation (QAM) schemes, the proposed non-binary LDPC-coded low complexity PDM-PS QAM scheme can obtain shaping gain, as evidenced through theoretical average mutual information and simulated error performance analyses. When the spectral efficiency is 4.5 bits/s/Hz, compared with the regular 64QAM system, the proposed 64QAM PDM-PS system can obtain 0.26 dB theoretical energy gain, while its simulated error performance is 0.30 dB. When the spectral efficiency is 6.0 bits/s/Hz, compared with the regular 256QAM system, the proposed 256QAM PDM-PS system can obtain 0.73 dB theoretical energy gain, while its simulated error performance is 0.93 dB. Compared with the conventional non-binary LDPC-coded PS QAM scheme, the proposed non-binary LDPC-coded PDM-PS QAM scheme can reduce the computational complexity by 33.1% and 49.7% under 64QAM and 256QAM, respectively, with acceptable error performance loss. The information-theoretic and error performance analyses both indicate the effectiveness and reliability of the proposed scheme.

A Comprehensive Analysis of PAPR Reduction in Scrambled UFMC and OFDM Using Artificial Bee Colony Algorithm for 5G Communications

ABSTRACT With the advent of 5G communications, the demand for high data rates and improved spectral efficiency has necessitated the exploration of advanced modulation techniques. Orthogonal Frequency Division Multiplexing (OFDM) and Universal Filtered Multi-Carrier (UFMC) are two prominent modulation schemes for 5G systems. However, both OFDM and UFMC suffer from a high Peak-to-Average Power Ratio (PAPR), leading to signal distortion and inefficient power amplification. The Partial Transmit Sequence (PTS) approach is a promising strategy to minimize PAPR in OFDM and is applied to UFMC to minimize PAPR in UFMC and is known as scrambled UFMC (S-UFMC). PTS, however, involves an extensive search to identify the best phase factors that increase computational complexity. The artificial bee colony algorithm is proposed to reduce the computational complexity S-UFMC and OFDM. A novel modulation scheme, amplitude phase shift keying (APSK), is used instead of quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) in S-UFMC and OFDM, which has better performance than conventional modulation schemes. In this research, OFDM, PTS OFDM, UFMC and S-UFMC are compared and it is found that the proposed scrambled UFMC with APSK modulation using ABC algorithm performs better than OFDM and UFMC in terms of PAPR, spectral efficiency and computational complexity.

Multimode TED-tuned beam mass damper for low-g capacitive MEMS accelerometers VRE reduction

Capacitive Micro-Electro-Mechanical Systems (MEMS) accelerometers for quasi-static applications are susceptible to vibration rectification error (VRE) when the ambient AC vibration signals get rectified to DC. Studies to mitigate the VRE have relied on the sigma-delta filtering algorithm with closed-loop feedback as well as the adoption of vibration-insensitive frequency modulation (FM) instead of conventional amplitude modulation. In this study, we propose a novel solution to VRE caused by asymmetric railing introducing multimode thermoelastic damping (TED) tuned beam mass damper (TBMD) integrated into the MEMS accelerometer effectively functioning as a compensator. Our contribution breaks through the microfabrication limitation of damping elements by utilizing intrinsic TED in MEMS material. The damper elements were alternately tuned up to the third flexural mode due to MEMS manufacturing constraints. This was done through parametric sweeps in numerical simulations on single-axis capacitive MEMS accelerometer integrated with multimode TED-damped TBMD. According to simulation results, the higher the mode shapes of the TED-damped tuned beam mass damper, the higher the damping effect and the better the vibration rectification factor.

Level vector pulse width modulation for multilevel inverters

SummaryIn this paper, a novel method named as level vector pulse width modulation (LVPWM) is proposed for multilevel inverters. Similar to the conventional space vector pulse width modulation (SVPWM), the proposed method is a vector‐based method in the α–β frame. Unlike the SVPWM, the variables of each of the α and β axes are considered separately. Instead of space vectors, level vectors are considered for the synthesis of the reference vectors. There is no need to consider multiple switching states, vectors, and large lookup tables in the algorithm. The appropriate switching states for the synthesis of the reference vectors are determined using simple computations at each sampling time. Generality for different inverter topologies, online implementation, simplicity of the algorithm and computations, independency of the algorithm complexity from the number of switching states, and easy extension to overmodulation region are the advantages of the proposed method. Implementation of the LVPWM in different inverter topologies is studied. The validation of the proposed modulation strategy is carried out by simulation and experimental results.

Adaptive DFT-s-OFDM employed novel multi layered scheme for reduction of PAPR for mMTC node in 5G (NR)

In 5G New Radio, The DFT-s-OFDM is a promising multiplexing technique for enhancing the average power of subcarriers to reduce the overall peak-to-average power ratio (PAPR). The peak of subcarrier is too high then the impact of DFT-s-OFDM is quite inferior. An Adaptive DFT-s-OFDM employed multilayered novel mechanism has been proposed in this research article to reduce the PAPR. The extent of sub-band is varied in accordance with predefined threshold value to enhance average power, meanwhile clipping is applied to shape the peak value of subcarrier. The clipping technique reduced the subcarrier’s peak power. The proposed approach has the greater impact in order to enhance the efficiency of non-linear Power Amplifier (PA). The PAPR is suppressed by the multilayered strategy in two ways. The first is the numerator element, which is the reduction of peak power by clipping operation, and the second is the denominator element, which is the improvement of average power through K-point DFT sub-band. The superior time–frequency localization of DFT-s-OFDM across uplink transmissions reduces the requirement for difficult node-to-node synchronization, which is potentially used by the mMTC nodes. The proposed adaptive DFT-s-OFDM modulation scheme performs better than conventional OFDM modulation, which is approximately 24% more effective at 6 dB.

Hybrid Control for Three-Level LLC Resonant Converter of Dual-Bridge for Wide Output Range

A three-level (TL) LLC resonant converter of dual-bridge (DB) with hybrid control modulation strategy is proposed for the wide output-voltage range and high input-voltage applications. The topology integrates two neutral-point-clamped arms (NPCs) through an auxiliary transformer, which forms a new controllable double-voltage structure and makes all MOSFETs hold half of the input voltage. Based on the characteristics of the new topology, a hybrid modulation strategy is proposed corresponding to three gain modes, which include conventional pulse frequency modulation (PFM) and fixed frequency phase shift modulation (FF-PSM). Compared to conventional modulation strategies, the proposed hybrid modulation strategy, which improves the output voltage gain range, achieves zero-voltage switching (ZVS) of all the MOSFETs and zero-current switching (ZCS) of rectifier diodes under wider operating voltage and full load range. To minimize the frequency window and improve the efficiency of the converter, the parameter optimization method is designed, which based on the characteristics of the modulation strategy and the relationship among the maximum output voltage gain, resonant current and turned-off current. At last, the experimental results of the 600W prototype are presented to confirm the theoretical and characterization analysis.

Generalized Multiphase-Shift Transient Modulation for Dual-Active-Bridge Series-Resonant Converter

Given the wide-range applications of bidirectional dual-active-bridge series-resonant converter (DABSRC), its complex nonlinear dynamic behavior is an interesting phenomenon that deserves attention of power electronics engineers. It is observed that if the control variables (i.e., phase-shift angles) are directly updated through conventional transient modulation, large-amplitude transient oscillations and dc offsets will be induced in the high-frequency-link voltages and currents during transient stage, which can ultimately degrade the converter's waveform quality significantly. The relatively few prior works in studying the transient oscillatory behavior of DABSRC have only focused on single-phase-shift modulation. In this article, a new transient modulation method referred to as generalized trajectory-switching modulation (GTSM) is first proposed for enhancing the transient performance of multi-phase-shift modulated DABSRC. GTSM can simultaneously mitigate the problems of transient oscillations and dc offsets regardless of operation modes and power-flow directions, thus always ensuring safe transient operation. It also enables the resonant voltages and currents as well as magnetizing current to seamlessly reach the desired new steady-state values swiftly. Finally, the said theoretical claims are verified experimentally under both open loop and closed loop with model predictive control, and the influence of deviations from nominal resonant tank's parameters on GTSM is also considered.

Polarization dynamics in spin‐VCSELs with integrated surface grating for high birefringence splitting

AbstractPolarization dynamics in spin‐polarized vertical‐cavity surface‐emitting lasers (spin‐VCSELs) with high birefringence have recently been demonstrated to offer very high potential for optical data‐transmission systems that outperform their counterparts based on conventional direct current modulation by far. For polarization dynamics in spin‐VCSELs, the birefringence determines the resonance frequency and thus the modulation bandwidth. In previous work, birefringence was controlled using mechanical strain, which lacks the ability to be integrated in standard VCSEL manufacturing processes. In this work the polarization dynamics of a VCSEL with an integrated birefringence control mechanism is demonstrated based on custom designed integrated surface gratings. It is found that, despite the surface grating which is commonly known to stabilize the polarization, the presented spin‐VCSELs are able to generate polarization oscillations with frequencies corresponding to the birefringence induced by the surface grating and show polarization dynamics up to 68 GHz.

DC-Side Soft-Switching Inverter With Modified Space-Vector Modulation Scheme

Three-phase soft-switching inverters are promising in order to reduce the losses in the switching devices and to reduce the electromagnetic interference produced by severe di/dt and dv/dt, which enables the operation of the inverter at higher switching frequency. This work proposes a DC-side three-phase zero-voltage soft-switching inverter topology that can be sub-categorized under actively clamped resonant dc-link topologies. Moreover, a modified space-vector modulation scheme is proposed, such that all the devices operate under zero-voltage switching condition. Compared to other similar dc-link soft-switching topologies, the proposed topology does not require feedback from the inverter output currents to achieve soft-switching operation. Unlike conventional space-vector modulation techniques, the proposed modified space-vector modulation does not require to turn-on the top and/or the bottom three switches of the two-level inverter at the same time to implement the zero vectors, which allows a reduction of the effective commutating time of the two-level inverter switches by one-third, during a grid voltage cycle. The auxiliary capacitor is only charged to a fraction of the dc bus voltage. Simulation and experimental results on a 10-kW and 100-kHz switching frequency lab-scale prototype are presented to demonstrate the validity and effectiveness of the proposed zero-voltage switching topology and modulation scheme on reducing the switching losses and electromagnetic interference.

Fixed Frequency LCC Resonant Converter Modeling and Optimal Design for High-Voltage Capacitor Charging Power Supply in Constant Power Control

LCC resonant converter is widely used in high-voltage capacitor charging power supply(CCPS) due to its high efficiency and utilization of parasitic parameters. Since CCPS generally demand a wide voltage variation range, the conventional frequency modulation is difficult to scale up in constant power control. In this paper, a phase-shift(PS) LCC resonant converter in constant power control is proposed. To solve the deviation of the shifted phase of the traditional method in constant power control, an accurate model based on state plane analysis(SPA) is built. On this basis, an optimal design method of PS-LCC for CCPS is proposed, which is helpful to realize the soft switching and reduce the current peak. Finally, a 10kV CCPS prototype is built. And experiment designed by proposed method realizes the constant power charging in PS-LCC for the first time. Experimental results show that the charging speed is increased by 44.3% compared with the traditional constant current charging. Besides, the current stress is reduced by 24.1% and the soft-switching range is extended by 6.9%. There is valuable engineering guidance for realizing high-efficiency and high-speed CCPS by the design method proposed.

Circulating Current Mitigation in Parallel Inverters by Dynamic Carrier Changing Technique

In parallel inverter system, power semiconductor switches conduct both load current and circulating current, caused by voltage difference between the inverters, which is due to (i) unequal power levels, (ii) interleaved PWM (for load current ripple reduction), and (iii) asymmetries such as unequal dead-time and device parasitics/tolerances. The circulating current incurs additional loss and reduces lifetime of converters. In this paper, it is established that the circulating current is proportional to Common Mode Voltage Difference (CMVD) between the inverters, that occurs during unequal load-sharing and interleaving. To reduce the circulating current, a dynamic carrier changing modulation technique is presented in this paper, by changing the phase of the carriers, based on the modulation angle of the modulating signals. The advantage of proposed technique is reduction of circulating current without affecting the load current ripple offered by conventional modulation techniques. The proposed technique can also reduce the circulating current in case of equal and unequal power sharing, and also when operated with DPWM techniques. Simulation and experimental results are presented to validate the effectiveness of the proposed modulation scheme.

Additional-Levels-based control method for modular multilevel converters with reduced DC-Link current ripple

The high and low order dc-link current ripple can be caused under balanced and unbalanced ac grid/load conditions for three-phase modular multilevel converters (MMCs). To enhance the dc-link current quality, this paper proposes an additional-levels-based control (ALC) method, where the conventional modulation is employed to generate ac-side voltage levels and a model predictive control (MPC) algorithm with reduced calculation burden is developed to produce additional levels for dc-link current performance improvement. Through evaluating the cost function of MPC, the proposed method can reduce both high and low order dc-link current ripple for the MMC. Meanwhile, it avoids disturbing the quality of the ac-side voltage. Besides, the calculation burden of the proposed method is independent of the submodules’ number per arm. The validity and effectiveness of the proposed method have been verified by simulation and experimental results.© 2017 Elsevier Inc. All rights reserved.

Stepped-Frequency Binary Offset Carrier Modulation for Global Navigation Satellite Systems

In this paper, we propose Stepped-Frequency Binary Offset Carrier (SFBOC) modulation for Global Navigation Satellite Systems (GNSS) that use spread spectrum signals. SFBOC modulation generates a Binary Offset Carrier (BOC) signal of which the subcarrier frequency varies stepwise within each period of the pseudorandom-noise (PRN) code. The generated SFBOC signal can have a sharp autocorrelation function (ACF) output and an almost flat spectrum over a wide frequency band. These characteristics result in correlation properties, multipath mitigation, and anti-interference that are superior to those of conventional GNSS modulations. To testify, we compare the performance of SFBOC in various aspects to conventional GNSS modulations and other time-varying subcarrier frequency (TVSF) modulations. From numerical simulations, we show that the proposed SFBOC has higher ranging accuracy, lower tracking ambiguity, and more robustness to noise, interference, and multipath than the conventional GNSS modulations. In addition, we demonstrate that the proposed SFBOC moulation has two advantages while other modulations with TVSF cannot have both; that SFBOC is robust to code-Doppler and that, when filterbank is employed, SFBOC improves the signal-to-noise ratio (SNR) significantly without any loss of weak early arrival path in the Non-line of sight (NLOS) multipath environments.

Power Distribution Method for Single-Phase Cascaded Multilevel Converters Based on Space Vector Modulation

Cascaded H-bridge converters are interesting candidates for photovoltaic (PV) and energy storage systems, since PV panels and/or batteries can be directly connected to the input dc-side of each converter module. However, differences in the parameters of the batteries or variable ambient conditions may result in energy imbalances among the power modules. In these cases, conventional modulation strategies will lead to an increased distortion on the converter output voltage. Therefore, this paper proposes a generalized space vector modulation for single-phase cascaded H-bridge converters considering the power processed by each power module and maintaining a low-THD multilevel output voltage waveform. The proposed method improves the converter output voltage harmonic spectrum compared to the conventional phase-shifted modulation strategy in cases of power imbalance among modules. Experimental results are included to demonstrate the performance of the proposed method.

Reduction of common mode voltage for grid-connected multilevel inverters using fuzzy logic controller

Cascaded multilevel three-phase inverters are increasing in industries of electric drives and renewable energy because of their large capacity and suffering from high voltage shock. However, the high magnitude of common mode voltage is one of the drawbacks. Thus, the techniques of modulation and control in these multilevel inverters significantly affect the power quality of the output voltage of inverters. This paper presents a technique using fuzzy logic technique for grid-connected cascaded multilevel 3-phase inverters. This technique has completely removed the current controllers and the conventional modulation using carriers. It also helps reduce the magnitude of common mode voltage and increase the dynamic response. Moreover, the ability to reduce harmonics and switching count also helps decrease the switching loss of inverter. The simulation results on a grid-connected cascaded 5-level 3-phase inverter have validated the effectiveness of the presented technique compared with that of the conventional method using phase opposition disposition (POD) and PI current controllers.

高周波IH応用単相ダイレクトAC-ACコンバータの固定周波数電力制御手法

The direct ac-ac converter is an effective circuit topology for high-efficient power conversion in induction heating (IH) applications. The conventional pulse frequency modulation (PFM)-based power control scheme causes audible noises between the adjacent IH loads which operate at different switching frequencies. As a solution for the technical issue, a new fixed-frequency power control methodology for a single-phase direct ac-ac converter is proposed in this paper, featuring a wide range of soft switching operation and robustness for abnormal load conditions. The principle of the proposed pulse modulation is explained in detail with the logic circuit diagram of controller. The performances of the ac-ac converter and power controller are demonstrated by simulation, after which the effectiveness is revealed in terms of the power control range and soft switching operation.

A unified bit-to-symbol mapping for generalized constellation modulation

Gray mapping is a well-known way to improve the performance of regular constellation modulation, but it is challenging to be applied directly for irregular alternative. To address this issue, in this paper, a unified bit-to-symbol mapping method is designed for generalized constellation modulation (i.e., regular and irregular shaping). The objective of the proposed approach is to minimize the average bit error probability by reducing the hamming distance (HD) of symbols with larger values of pairwise error probability. Simulation results show that the conventional constellation modulation(i.e., phase shift keying and quadrature amplitude modulation (QAM) with the proposed mapping rule yield the same performance as that of classical gray mapping. Moreover, the recently developed golden angle modulation (GAM) with the proposed mapping method is capable of providing around 1 dB gain over the conventional mapping counterpart and offers comparable performance to QAM with Gray mapping.