Carrier Modulation Research Articles

Improved MBOC modulations based on periodic offset subcarrier

With the development of global navigation satellite systems, the modernization of global navigation satellite systems has arrived, which takes the binary offset carrier modulation and related evolution as the typical feature. Moreover, the performance of multiplexed binary offset carrier modulation is related to global navigation satellite systems service. In the paper, an improved multiplexed binary offset carrier modulation based on period offset subcarrier was proposed, called MBOC-POS, where the subcarrier periodic shifting binary offset carrier modulation is used as the lower-order component instead of sine-binary offset carrier modulations. Meanwhile, the different implementations of MBOC-POS modulations are analysed and compared with traditional multiplexed binary offset carrier multiplexed binary offset carrier signals in multipath mitigation, tracking accuracy, anti-interference and compatibility. By simulation and analysis, the performance of reconstructed MBOC-POS modulation has been improved. Especially, for the mismatch reception, the Gabor bandwidth increases by 29.5% and the multipath error envelope is reduced by 35% with the filter bandwidth of 10 MHz. Therefore, the multiplexed binary offset carrier MBOC-POS modulation proposed in the paper can be used as a new option for MBOC modulations and next-generation signal design.

Radiation Defects and Carrier Lifetime in 4H‐SiC Bipolar Devices

The effect of radiation damage on the minority carrier lifetime in the 4 H‐SiC epilayers forming the n‐base of the power p–i–n diodes is presented. Irradiation with fast neutrons and MeV protons is used for uniform and local lifetime reduction. Deep‐level transient spectroscopy in combination with open‐circuit voltage decay measurement shows that the carrier lifetime is reduced by increased carrier recombination on Z1/Z2, EH3, and possibly RD4 levels. The lifetime degrades swiftly and the ON‐state carrier modulation capability of high‐voltage devices can be easily lost already at very low fluences. The results further show that the proton irradiation provides an excellent tool for local lifetime tailoring. The carrier lifetime can be easily set by proton fluence and localized by proton energy. The proper local lifetime reduction speeds up diode recovery without an undesirable increase in the forward voltage drop. However, attention must be taken to properly locate the damage maximum so as not to increase device leakage.

Research on the performance of a novel electro-hydraulic proportional directional valve with position-feedback groove

Accurate posture control of hydraulic roof supports, which use pressurized water as their fluid power source, is an important part and research direction of intelligent fully mechanized mining face. At present, the large flow on/off directional valve used on the hydraulic roof support cannot meet the requirement of precise posture control of the roof support. To overcome the conundrum, a novel two-position three-way electro-hydraulic proportional directional flow valve for hydraulic roof support is proposed. The new valve contains two pilot stages and two main spools. The two pilot stages cooperate with each other to control the movement of the two main valve spools, which are the inlet valve spool and the outlet valve spool. The inlet valve spool adopts the Valvistor principle. The valve can realize manual pilot control and electro-hydraulic proportional flow control of the passage P-A, which has been verified by a simulation model. In this paper, the static and dynamic mathematical models of the new proportional valve are established, and the key parameters affecting the valve performances are analyzed and verified by the simulation model. An optimization control scheme is proposed to overcome the influence of supply pressure, P-A pressure difference, and nonlinear interference force on steady-state displacement and response speed of the valve. The results show that this optimization method can significantly improve the response speed of the spool and promote the linearity of spool displacement under a slope signal. In addition, the fluctuation of chamber pressure and spool displacement caused by the discontinuous flow of a fast switching valve is systematically analyzed. The analysis shows that increasing pulse-width modulation carrier frequency is an effective way to reduce fluctuation amplitude. The research provides a new design idea and control method for an electro-hydraulic proportional directional valve of hydraulic roof support.

RETRACTED ARTICLE: A comprehensive survey 5G wireless communication systems: open issues, research challenges, channel estimation, multi carrier modulation and 5G applications

RETRACTED ARTICLE: A comprehensive survey 5G wireless communication systems: open issues, research challenges, channel estimation, multi carrier modulation and 5G applications

Performance analysis of differential quadrature phase shift keying modulation schemes for a radio over fiber system

Radio over fiber systems have become one of the best options for backhaul due to their larger bandwidth, low propagation loss, and competitive cost. Advanced modulation formats play a key role in enhancing the performance of fiber optic communication systems by providing higher bit rates and less susceptibility to noise in long distance transmission. This paper presents a detailed analysis of differential quadrature phase shift keying modulation in a radio over fiber system at 60 GHz for 5G applications. The differential quadrature phase shift keying modulation is combined with two different advanced phase modulation formats, i.e., return-to-zero and carrier suppressed return-to-zero to provide higher spectral efficiency. The performance of the system has been investigated at 10 and 20 Gbps data rates for 10 to 50 km transmission lengths of different types of fiber. Overall, it has been observed that carrier suppressed return-to-zero differential quadrature phase shift keying is better as compared with return-to-zero differential quadrature phase shift keying at both 10 and 20 Gbps data rates up to a transmission length of 50 km.

Charge carrier modulation in dual-gated graphene field effect transistor using honey as polar organic gate dielectric

Charge carrier modulation of graphene-based field effect transistors (GFETs) is the key factor to utilize and enhance its fascinating properties for technological applicability. Here, we have demonstrated the gate-dependent tweaking of electrical properties of graphene devices by application of honey as a top gate dielectric. Electrical characterization of dual-gated GFET is elucidated at different top and back-gate voltages. A charge neutrality point is fine-tuned by varying the top gate voltage (Vtg) from + 3 to − 4 V. The change in carrier density is clearly observed from 3.66 × 1012 to 2.15 × 1011 cm−2 at + 3 to − 4 Vtg. The charge carrier mobility of gel-gated GFET is increased significantly to 5376 cm2/V ⋅ sec by increasing top-gate voltages up to − 4 V. Result demonstrates a cost-effective, facile and rapid fabrication of top-gated devices and suggest natural dielectric materials as good candidate to replace conventionally available gate dielectrics in FET technology.

A Novel Approach for the Characterization of Triangular Modulated Frequency Modulated Continuous Wave Low Probability of Intercept Radar Signals via Application of the Wigner-Ville Distribution

Digital intercept receivers are changing from Fourier-based analysis to classical time-frequency analysis techniques for analyzing low probability of intercept radar signals. This paper presents a novel approach of characterizing low probability of intercept triangular modulated frequency modulated continuous wave radar signals through utilization and direct comparison of the signal processing techniques Wigner-Ville Distribution versus the Reassigned Smooth Pseudo Wigner-Ville Distribution. The following metrics were used for evaluation: percent error of: carrier frequency, modulation bandwidth, modulation period, chirp rate, and time-frequency localization (x and y direction). Also used were: percent detection, lowest signal-to-noise ratio for signal detection, and plot (processing) time. Experimental results demonstrate that overall, the Reassigned Smooth Pseudo Wigner-Ville Distribution signal processing technique produced more accurate characterization metrics than the Wigner-Ville Distribution signal processing technique.

Intercalating ultrathin polymer interim layer for charge transfer cascade towards solar-powered selective organic transformation

Transition metal chalcogenide quantum dots (TMCs QDs) constitute a crucial sector of semiconductors on account of large absorption coefficient for light harvesting, peculiar quantum confinement effect, and abundant active sites stemming from ultra-small size. However, elaborate and tunable modulation of anisotropic photoinduced charge carriers over TMCs QDs represents an enduring challenge in terms of sluggish charge transfer kinetic and ultra-short charge lifetime compared with nanoparticulate counterparts, thereby rendering maneuvering charge transfer of TMCs QDs a tough issue. We herein conceptually unlock the unanticipated charge transport capability of solid-state non-conductive poly(diallyl dimethylammonium chloride) (PDDA) for constructing cascade charge transfer pathway over self-assembled wide bandgap semiconductors (WBS)/PDDA/TMCs QDs multilayered heterostructures, by which unidirectional and accelerated electron transfer from TMCs QDs to WBS support mediums was spontaneously activated, markedly boosting the charge separation/migration efficiency. The integrated roles of such ultrathin insulating PDDA intermediate layer as simultaneous surface charge modifying agent and interfacial charge transfer mediator have been evidenced to be universal. The unexpected electron-withdrawing capability of ultrathin PDDA layer endows WBS (SnO2, TiO2)@PDDA@TMCs (CdSe, CdS) QDs heterostructures with significantly enhanced net efficiency of photoactivities toward selective anaerobic reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would feature a promising scope for rational design of multifarious novel insulating polymers-based photosystems for solar energy conversion.

An interferometric vibrometer using phase carrier generated by liquid surface acoustic waves and an improved phase demodulation scheme

A novel phase carrier generation method for a sinusoidal phase-modulating laser homodyne interferometric vibrometer is proposed in this paper. In this homodyne interferometer scheme, phase modulation of the reference arm is achieved with liquid surface acoustic waves, a technique that is generally considered to be low in cost. The mathematical model for vibration detection signals using the proposed interferometer scheme is analyzed. To facilitate application of the new interferometer scheme, an improved phase-generated carrier arctangent (PGC-Arctan) approach algorithm based on real-time normalization of orthogonal interference signal pair is proposed to eliminate non-linear demodulation errors due to changes of interference signal parameters, such as changes of carrier phase delay and signal visibility caused by thermal capillary waves on liquid surface, and changes of phase modulation depth caused by amplitude fluctuations of liquid surface acoustic waves (LSAWs). In this method, the amplitude attenuation of low frequency components in the vibration detection signal after carrier frequency shift is used to estimate the phase modulation depth, and an orthogonal carrier signal is introduced to estimate the carrier phase delay in real time. Finally, an orthogonal interference signal pair is normalized by using the estimated values of the phase modulation depth and carrier phase delay. The feasibility of the proposed method is proved by numerical simulation and vibration measurement experiments. The experimental results show that the average THD is -43.82 dB for the sinusoidal vibration with the frequency of 10 Hz.

Modulation of Fe-based oxygen carriers by low concentration doping of Cu in chemical looping process: Reactivity and mechanism based on experiments combined with DFT calculations

Fe-based oxygen carriers (OCs) are currently the crucial material basis for chemical looping technology to realize industrial applications. However, the relatively low reactivity of pure Fe-based OCs limits their extensive applications. One strategy to enhance reactivity in the chemical looping process is the introduction of another metallic element by doping. This study prepared a series of Fe-based OCs (Cu2xFe2(1-x)O3) with low concentration doping of Cu. The reaction mechanism and reactivity modulation of Cu2xFe2(1-x)O3 OCs in the chemical looping process were systematically investigated by means of experiments and density function theory (DFT) calculations. Activation energies for Cu2xFe2(1-x)O3 ranging between 72 and 37 kJ/mol were detected using H2 and the thermogravimetric analyzer (TGA) test, indicating enhanced reactivity in the chemical looping process as compared with that of pure Fe-based OCs of 84 kJ/mol. Thus, the low concentration doping of Cu can effectively improve the reactivity of Fe-based OCs. Furthermore, comprehensive DFT calculations upon the transition state indicated the reaction energy barrier for Cu2xFe2(1-x)O3 with different doping concentration and configurations to be in the range of 1.68–1.02 eV, lower than that of pure Fe2O3 of 2.30 eV. The Cu doping and the modulation of the reaction pathways are important reasons for the enhanced reactivity of Cu2xFe2(1-x)O3 OCs. Additionally, this study proposed a lattice oxygen release mechanism of Cu2xFe2(1-x)O3 OCs during chemical looping combustion.

Fiber-optic distributed acoustic sensor utilizing LiNbO3 straight through waveguide phase modulator.

A novel fiber-optic distributed acoustic sensor (DAS) utilizing a LiNbO3 straight through waveguide phase modulator as phase generation carrier (PGC) modulation module for the detection of acoustic signal is presented. The sensitive principle and the phase demodulation method of the system based on phase-sensitive optical time domain reflectometer (Φ-OTDR) are described. This scheme solves the problems of low modulation frequency and unstable performance of piezoelectric transducer (PZT) in the traditional homodyne detection system and depends only on the pulse repetition frequency. The efficacy of the new approach is demonstrated experimentally, showing that the weak acoustic signal can be demodulated accurately. The noise level of the system is < 4.2×10-3 rad/√Hz, the signal to noise ratio (SNR) is > 16 dB, and the spatial resolution is 10 m, as well as a detection frequency can theoretically achieve 25 kHz at 2 km sensing fiber. It provides a new research idea for DAS and is expected to replace PZT to achieve a high-frequency response, which has good potential in the applications of low cost, long distance and high frequency detection.

Noise Reduction Method for Low Voltage Power Line Carrier Communication

In order to improve the performance of electricity information collection system, this paper studies and proposes a new method of low-voltage power line carrier signal frequency domain noise reduction. It includes frequency domain decomposition of carrier signal, filtering noise reduction and signal frequency domain restoration. Then compared our method with the wavelet packet noise reduction method based on multi-resolution. The experimental results show that the proposed algorithm is better than the comparison algorithm under different modulation modes and carrier frequencies, especially suitable for carrier signal noise reduction under bad channel conditions. The algorithm proposed in this paper has good anti signal attenuation performance, and it can effectively enhance the SNR, and ensure the transmission performance and system reliability of the electricity information collection system.

MoTe2 on ferroelectric single-crystal substrate in the dual-gate field-effect transistor operation

An exfoliated MoTe2 flake in contact with a ferroelectric single-crystal substrate was studied to examine its charge carrier modulation by neighboring ferroelectric polarization. A MoTe2 field-effect transistor was fabricated, having a hexagonal-BN (hBN) flake and a ferroelectric substrate employed as top and bottom gate dielectrics. In the dual-gate operation, the charge conduction exhibited an ambipolar behavior with large hysteresis during the gate voltage sweep. It mainly originates from the ferroelectric nature in combination with the charge trap phenomena at the interfaces. Interestingly, we found out that holes are more easily trapped than electrons, and charge carriers in MoTe2 are easily modulated through the top hBN gate when the electron conduction is predominantly set by the bottom ferroelectric field. However, the controllability becomes much weaker under opposing ferroelectric polarizations. This unbalanced controllability reveals the interfacial hole-trap effect resulting from ferroelectric polarization.

Design and Performance Analysis of THz Wireless Communication Systems for Chip-to-Chip and Personal Area Networks Applications

Terahertz (THz) communication is a promising technique for chip-to-chip communication and wireless personal area networks. In this paper, we present an experimental study and design to realize such THz communication systems. We develop two different chip sets for on-off-keying (OOK) modulation based THz transceivers which include carrier generators, modulators, THz amplifiers, and baseband amplifiers. Specifically, the first chip set integrates the circuit blocks for the OOK modulation without the THz amplifier for short-range communication. In addition, the second chip set design includes the THz amplifier modules to extend the coverage of transmission. For these two chip sets, we experimentally demonstrate the feasibility of the wireless communication at THz frequency bands and assess performance using the bit error rate (BER) analysis. We estimate the BER by calculating the signal-to-noise ratio (SNR) based on the eye diagram and compare with actual BER measurements and Monte Carlo simulations. We also address the impact of the distance, the transmit power, and the data rate for the proposed THz transceivers based on the link budget analysis, and confirm the accuracy of the derived BER expression.

Computationally Efficient PM Power Loss Mapping for PWM Drive Surface-Mounted Permanent Magnet Synchronous Machines

This paper proposes a computationally efficient approach for mapping permanent magnet (PM) power loss in permanent magnet synchronous machines (PMSMs). The PM loss mapping method here uses time-step finite element analysis (FEA) to determine the function parameters representing the loss variation with speed (frequency), amplitude modulation ratio, carrier ratio, and stator current and is suitable for rapid evaluation of machine performance over the entire torque–speed envelope. The PM loss can be accurately mapped across the full operational envelope, including the field-weakened mode. The loss mapping procedure takes into account the equivalent resistivity of axial segmentation of the PM array calculated by three-dimensional (3-D) FEA. The effect of temperature on the PM loss is also considered. The proposed methodology is validated on two surface-mounted PMSM designs. The results of the loss mapping procedure are consistent with those from direct 3-D finite element prediction and experimental results of PM power loss at each operating point of the machine.

A Janus compatible software-defined underwater acoustic multiple-input multiple-output modem

This article describes the implementation of a multiple-input multiple-output acoustic communication link in shallow water conditions to enable a software-defined acoustic modem with a maximum transmission rate of 20 kbps in a 5-kHz bandwidth. The reliability improvement of a low-complexity Alamouti space–time block code is evaluated to improve the diversity in a high-rate transmission mode using single carrier modulation, as well as in a low-rate transmission mode relying on continuous-phase frequency-shift keying. Using measurements in realistic subsea conditions, the effect of the spatial channel correlation is demonstrated. It is found that for the space–time block code/continuous-phase frequency-shift keying, the spatial diversity is significantly degraded due to the high spatial correlation. In contrast, for the high-mode transmission rate, space–time block code with single carrier modulation offers a bit error rate improvement by a factor over hundred, in comparison to a single transmit element, demonstrating that the multiple-input multiple-output optimal code depends on the software-defined acoustic modem transmission mode.

Optical FMCW Signal Generation Using a Silicon Dual-Parallel Mach-Zehnder Modulator

We experimentally demonstrate optical frequency-modulated continuous-wave (FMCW) signal generation utilizing a silicon dual-parallel Mach-Zehnder modulator (DP-MZM). The sideband suppression ratio (SSR) and the sideband-to-carrier suppression ratio (SCSR) of the single-sideband suppressed carrier (SSB-SC) modulation are higher than 15 dB when RF frequency is lower than 20 GHz. With the generated triangular modulated FMCW signal, we demonstrate simultaneous ranging and velocimetry. The chirp bandwidth is 10 GHz and the chirp period is 1 μs, corresponding to a ranging resolution of 13 mm and a velocimetry resolution of 0.5 m/s, consistent with the theoretical calculation. These results show that wideband FMCW signal generation by a silicon DP-MZM is promising for high-resolution light detection and ranging.

An Unambiguous Synchronization Scheme for GNSS BOC Signals Based on Reconstructed Correlation Function.

Binary offset carrier (BOC) modulation is a new modulation method that has been gradually applied to the Global Satellite Navigation System (GNSS) in recent years. However, due to the multi-peaks in its auto-correlation function (ACF), it will incur a false lock and generate synchronization ambiguous potentially. In this paper, an unambiguous synchronization method based on a reconstructed correlation function is proposed to solve the ambiguity problem. First, through the shape code vector constructed in this paper, the general cross-correlation function (CCF) expression of the BOC modulated signal will be obtained. Based on the features of the signal correlation function, it is decomposed into a matrix form of trigonometric functions. Then, it generates two local signal waves using a specific method, then the proposed method is implemented to obtain a no-side-peak correlation function by reconstructing the cross-correlation between the received signal and the two local signals. Simulations showed that it fully eliminates the side-peak threat and significantly removes the ambiguity during the synchronization of the BOC signals. This paper also gives the improved structure of acquisition and tracking. The detailed theoretical deduction of detection probability and code tracking error is demonstrated, and the corresponding phase discrimination function is given. In terms of de-blurring ability and detection probability performance, the proposed method outperformed other conventional approaches. The tracking performance was superior to the comparison methods and the phase discrimination curve only had a zero-crossing, which successfully removed the false lock points. In addition, in multipath mitigation, it outperformed the ACF of the BOC signal, and performs as well as the autocorrelation side-peak cancellation technique (ASPeCT) for BOC(kn,n) signals.

Simultaneous transmission of clock and data signals in photonic-assisted WDM passive optical networks

This work reports on the use of a gain-switched vertical cavity surface-emitting laser (VCSEL) optical frequency comb (OFC) to generate multiple optical carriers for applications in future wavelength-division multiplexing (WDM) passive optical network (PON) systems. The VCSEL-based OFC system was tested for its ability to simultaneously transmit error-free data signals up to 30 Gbps, and a 50 MHz clock signal proposed to be used for latency monitoring of the network. The system was demonstrated over a fiber distance beyond 20 km. Four optical carrier signals were filtered from the generated OFC. Three of the four optical carriers were combined and amplitude-modulated with 5 and 10 Gbps on–off keying (OOK) data signals. The fourth optical carrier was amplitude-modulated with a 50 MHz clock signal. These four modulated optical carriers were multiplexed and transmitted over 21 km of standard single-mode fiber. When the three data-carrying optical carriers were modulated with 5 Gbps OOK data and multiplexed with the clock-carrying carrier, a negligible transmission penalty was achieved after fiber transmission. When these three data-carrying optical carriers were modulated with 10 Gbps OOK data and multiplexed with a clock-carrying carrier, a maximum transmission penalty of 4.8 dB was achieved after fiber transmission. The system was investigated at a minim bit error rate (BER) of 10 − 9 . A receiver sensitivity of less than − 11 d B m was achieved at both bit rates. The clock signal suffered little effect when transmitted with the three optical carriers at both 5 and 10 Gbps data rate. A power penalty of 15.37 dB, mainly due to fiber attenuation, was experienced in the clock after fiber transmission. Due to the unavailability of the numerical system to quantify the clock performance in terms of phase noise, the phase-noise results could not be provided. Nevertheless, the provided qualitative results were able to show that the transmitted clock integrity was able to be retained after being multiplexed with transmission on the 21 km fiber channel. For the first time, to the best of our knowledge, we have simultaneously reported on data and clock transmission results using a low-power, VCSEL-based OFC to realize a WDM-PON system. These results are attractive as they demonstrate and motivate the possibility of using gain-switched VCSELs as OFC sources in future WDM-PON networks requiring enhanced channel capacity and stringent network latency monitoring to realize intelligent, simple, and power-efficient PON networks.

Photonic generation of quadruple bandwidth dual-band dual-chirp microwave waveforms with immunity to power fading.

A photonic method to generate and transmit quadruple bandwidth dual-band dual-chirp microwave waveforms with immunity to fiber chromatic dispersion induced power fading is proposed and experimentally demonstrated, which is suitable for Doppler blind-speed elimination, small target detection, and multiband detection in multiband radar systems. A dual-polarization dual-parallel Mach-Zehnder modulator is utilized to realize carrier-suppressed harmonic single-sideband modulation of a radio frequency carrier and carrier-suppressed DSB modulation of a baseband single-chirped waveform at two orthogonal polarization states. After photoelectronic conversion, dual-band bandwidth-quadrupling dual-chirp waveforms are generated. Moreover, different from traditional DSB-based dual-chirp signal generation, the generated dual-chirp microwave waveforms can be transmitted over fiber without power fading, which is significant in dual-band radars for one to multiple base station transmissions.