Paraelectric Doping Simultaneously Improves the Field Frequency Adaptability and Dielectric Properties of Ferroelectric Materials:A Phase-Field Study

Recent years,the polarization response of ferroelectrics has been entirely studied.However,it is found that the polarization may disappear gradually with the continually applied of electric field.In this paper,taking K0.48Na0.52NbO3(KNN)as an example,it was demonstrated that the residual polarization began to decrease when the electric field frequency increased to a certain extent using a phase-field methods.The results showed that the content of out-of-plane domains increased first and then decreased with the increase of applied electric field frequency,the maximum polarization disappeared at high frequencies,and the hysteresis loop became elliptical.In order to further study the abnormal changes of hysteresis loops of ferroelectrics under high electric field frequency,we analyzed the hysteresis loop and dielectric response of solid solution 0.1SrTiO_(3)-0.9K_(0.48)Na_(0.52)NbO_(3).It was found that the doped hysteresis loop maintained its shape at higher frequency and the dielectric constant increased.This kind of doping has a higher field frequency adaptability,which has a key guiding role in improving the dielectric properties of ferroelectric thin films and expanding the frequency application range of ferroelectric nano memory。

Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift

A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.

Phase field model for electric-thermal coupled discharge breakdown of polyimide nanocomposites under high frequency electrical stress

In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of Polyimide(PI) composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of Joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.

Fast-Lock Low-Jitter PLL with a Simple Phase-Frequency Detector

A fast-locking, low-jitter, phase-locked loop （PLL） with a simple phase-frequency detector is proposed. The phase-frequency detector is composed of only two XOR gates. It simultaneously achieves low jitter and short locking time. The voltage-controlled oscillator within the PLL consists of four-stage ring oscillators which are coupled to each other and oscillate with the same frequency and a phase shift of 45. The PLL is fabricated in 0. 1Stem CMOS technology. The measured phase noise of the PLL output at 500kHz offset from the 5GHz center frequency is - 102.6dBc/Hz. The circuit exhibits a capture range of 280MHz and a low RMS jitter of 2.06ps. The power dissipation excluding the output buffers is only 21.6roW at a 1.8V supply.

Coherent optical frequency transfer via 972-km fiber link

We demonstrate coherent optical frequency dissemination over a distance of 972 km by cascading two spans where the phase noise is passively compensated for.Instead of employing a phase discriminator and a phase locking loop in the conventional active phase control scheme,the passive phase noise cancellation is realized by feeding double-trip beat-note frequency to the driver of the acoustic optical modulator at the local site.This passive scheme exhibits fine robustness and reliability,making it suitable for long-distance and noisy fiber links.An optical regeneration station is used in the link for signal amplification and cascaded transmission.The phase noise cancellation and transfer instability of the 972-km link is investigated,and transfer instability of 1.1×10^(-19)at 10^(4)s is achieved.This work provides a promising method for realizing optical frequency distribution over thousands of kilometers by using fiber links.

Robust CMOS phase frequency detector for high speed and low jitter charge pump PLL

In order to improve the performance of the existing phase frequency detectors （PFDs）, a systematical analysis of the existing PFDs is presented. Based on the circuit architecture, both classifications and comparisons are made. A new robust CMOS phase frequency detector for a high speed and low jitter charge pump phrase-locked loop （PLL） is designed. The proposed PFD consists of two rising-edge triggered dynamic D flip-flops, two positive-edge detectors and delaying units and two OR gates. It adopts two reset mechanisms to avoid the LIP and DN signals to be logic-1 simultaneously. Thus, any current mismatch of the charge pump circuit will not worsen the performance of the PLL. Furthermore, it has hardly any dead-zone phenomenon in phase characteristic. Simulations with ADS are performed based on a TSMC 0. 18-μm CMOS process with a 1.8-V supply voltage. According to the theoretical analyses and simulation results, the proposed PFD shows a satisfactory performance with a high operation frequency （≈ 1 GHz）, a wide phase-detection range [ ± 2π], a near zero dead-zone （ 〈 0. 1 ps）, high reliability, low phase jitter, low power consumption （ ≈100 μW） and small circuit complexity.

Modulation Recognition with Frequency Offset and Phase Offset over Multipath Channels

Modulation recognition becomes unreliable at low signal-to-noise ratio(SNR)over fading channel.A novel method is proposed to recognize the digital modulated signals with frequency and phase offsets over multi-path fading channels in this paper.This method can overcome the effects of phase offset,Gaussian noise and multi-path fading.To achieve this,firstly,the characteristic parameters search is constructed based on the cyclostationarity of received signals,to overcome the phase offset,Gaussian white noise,and influence caused by multi-path fading.Then,the carrier frequency of the received signal is estimated,and the maximum characteristic parameter is searched around the integer multiple carriers and their vicinities.Finally,the modulation types of the received signal with frequency and phase offsets are classified using decision thresholds.Simulation results demonstrate that the performance of the proposed method is better than the traditional methods when SNR is over 5dB,and that the proposed method is robust to frequency and phase offsets over multipath channels.

Design of 0.5V low-voltage phase and frequency detector for frequency synthesizer in wireless sensor networks

Based on 0.13μm complementary metal-oxide-semiconductor（CMOS） technology,a phase and frequency detector（PFD） is designed with a low supply voltage of 0.5V for frequency synthesizers used in wireless sensor networks（WSNs）.The PFD can compare the frequency and phase differences of input signals and deliver a signal voltage proportional to the difference.Low threshold transistors are used in the circuits since a power supply of 0.5V is adopted.A pulse latched structure is also used in the circuits in order to increase both the detection range of phase errors and the maximum operation frequency.In experiments,a phase error with a range from-358° to 358° is measured when the input signal frequency is 2MHz.The PFD has a faster acquisition speed compared with conventional digital PFDs.When the input signals are at a frequency of 2MHz with zero phase error,the circuits have a power consumption of 1.8[KG＊8]μW,and the maximum operation frequency is 1.25GHz.

A Low-Power High-Frequency CMOS Peak Detector

A low-power,high-frequency CMOS peak detector is proposed. This detector can detect RF signal and base-band signal peaks. The circuit is designed using SMIC 0.35μm standard CMOS technology. Both theoretical calculations and post simulations show that the detection error is no more than 2% for various temperatures and processes when the input amplitude is larger than 400mV. The detection bandwidth is up to 10GHz, and its static current dissipation is less than 20μA.

A wideband low-phase-noise LC VCO for DRM/DAB frequency synthesizer

The wideband CMOS voltage-controlled oscillator（VCO）with low phase noise and low power consumption is presented for a DRM/DAB（digital radio mondiale and digital audio broadcasting）frequency synthesizer.In order to obtain a wide band and a large tuning range,a parallel switched capacitor bank is added in the LC tank.The proposed VCO is implemented in SMIC 0.18-μm RF CMOS technology and the chip area is 750 μm×560 μm,including the test buffer circuit and the pads.Measured results show that the tuning range is 44.6%;i.e.,the frequency turning range is from 2.27 to 3.57 GHz.The measured phase noise is-122.22 dBc/Hz at a 1 MHz offset from the carrier.The maximum power consumption of the core part is 6.16 mW at a 1.8 V power supply.

A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals

A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.

Adaptive compensating method for Doppler frequency shift using LMS and phase estimation

The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the phase offsets due to frequency shift are linear. Based on this premise, the compensation processes are： firstly, the phase offsets between the baseband neighbor-symbols after clock recovery is unbiasedly estimated among the reference symbols; then, the receiving signals symbols are adjusted by the phase estimation value; finally, the phase offsets after adjusting are compensated by the least mean squares （LMS） algorithm. In order to express the compensation processes and ability clearly, the quadrature phase shift keying （QPSK） modulation signals are regarded as examples for Matlab simulation. BER simulations are carried out using the Monte-Carlo method. The learning curves are obtained to study the algorithm＇s convergence ability. The constellation figures are also simulated to observe the compensation results directly.

Discrimination of Motor Imagery Patterns by Electroencephalogram Phase Synchronization Combined With Frequency Band Energy

Central nerve signal evoked by thoughts can be directly used to control a robot or prosthetic devices without the involvement of the peripheral nerve and muscles.This is a new strategy of human-computer interaction.A method of electroencephalogram(EEG) phase synchronization combined with band energy was proposed to construct a feature vector for pattern recognition of brain-computer interaction based on EEG induced by motor imagery in this paper,rhythm and beta rhythm were first extracted from EEG by band pass filter and then the frequency band energy was calculated by the sliding time window;the instantaneous phase values were obtained using Hilbert transform and then the phase synchronization feature was calculated by the phase locking value(PLV) and the best time interval for extracting the phase synchronization feature was searched by the distribution of the PLV value in the time domain.Finally,discrimination of motor imagery patterns was performed by the support vector machine(SVM).The results showed that the phase synchronization feature more effective in4s-7s and the correct classification rate was 91.4%.Compared with the results achieved by a single EEG feature related to motor imagery,the correct classification rate was improved by 3.5 and4.3 percentage points by combining phase synchronization with band energy.These indicate that the proposed method is effective and it is expected that the study provides a way to improve the performance of the online real-time brain-computer interaction control system based on EEG related to motor imagery.

Cognitive anti-jamming receiver under phase noise in high frequency bands

This paper investigates the jamming sensing performance of the simultaneous transmit and receive based cognitive anti-jamming(SCAJ) receiver impaired by phase noise in local oscillators(LO) over fading channels. Firstly, energy detection(ED)based on the jamming to noise ratio(JNR) of the high frequency bands SCAJ receiver with phase noise under different channels is analyzed. Then, the probabilities of jamming detection and false alarm in closed-form for the SCAJ receiver are derived. Finally,the modified Bayesian Cramer-Rao bound(BCRB) of jamming sensing for the SCAJ receiver is presented. Simulation results show that the performance degradation of the SCAJ system due to phase noise is more severe than that due to the channel fading in the circumstances where the signal bandwidth(BW) is kept a constant. Moreover, the signal BW has an effect on the phase noise in LO, and the jamming detection probability of the wideband SCAJ receiver with lower phase noise outperforms that of the narrowband receiver using the same center frequency. Furthermore,an accurate phase noise estimation and compensation scheme can improve the jamming detection capability of the SCAJ receiver in high frequency bands and approach to the upper bound.

Microwave frequency transfer over a 112-km urban fiber link based on electronic phase compensation

We demonstrate the transmission of a microwave frequency signal at 10 GHz over a 112-km urban fiber link based on a novel simple-architecture electronic phase compensation system.The key element of the system is the low noise frequency divider by 4 to differentiate the frequency of the forward signal from that of the backward one,thus suppressing the effect of Brillouin backscattering and parasitic reflection along the link.In terms of overlapping Allan deviation,the frequency transfer instability of 4.2×10-15 at 1-s integration time and 1.6×10-18 at one-day integration time was achieved.In addition,its sensitivity to the polarization mode dispersion in fiber is analyzed by comparing the results with and without laser polarization scrambling.Generally,with simplicity and robustness,the system can offer great potentials in constructing cascaded frequency transfer system and facilitate the building of fiber-based microwave transfer network.

An improved frequency shift method for ATI-SAR flat earth phase removal

An improved frequency shift method is proposed to remove the flat earth phase in ATI-SAR ocean surface motion detection in this study. First, two conventional flat earth effect removal methods(i.e., the frequency shift method and the orbital parameter method) are introduced and compared. Then, two improvements to frequency shift method are suggested. In the first improvement, the phase diagram is divided into several sub-blocks to calculate the phase fringe frequency. In the second improvement, a function between the phase of land regions and position is fitted to correct the residual flat earth phase based on the phase of the land regions that tend toward zero in an along-track interferogram. It is found that the improved frequency shift method is greatly improved;and it agrees well with the orbital parameter method, and achieves similar accuracy.

Joint Estimation of Carrier Frequency and Phase Offset Based on Pilot Symbols in Quasi-Constant Envelope OFDM Satellite Systems

Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high spectral efficiency and low peak-to-average power ratio(PAPR). Therefore, the QCE-OFDM technique is considered as a promising candidate multi-carrier technique for satellite systems. However, the Doppler effect will cause the carrier frequency offset(CFO), and the non-ideal oscillator will cause the carrier phase offset(CPO) in satellite systems. The CFO and CPO will further result in the bit-error-rate(BER) performance degradation. Hence, it is important to estimate and compensate the CFO and CPO. This paper analyzes the effects of both CFO and CPO in QCE-OFDM satellite systems. Furthermore, we propose a joint CFO and CPO estimation method based on the pilot symbols in the frequency domain. In addition, the optimal pilot symbol structure with different pilot overheads is designed according to the minimum Cramer-Rao bound(CRB) criterion. Simulation results show that the estimation accuracy of the proposed method is close to the CRB.

OSCILLATION FREQUENCY THEORY OF A PIEZOELECTRIC SENSOR INLIQUID PHASE WITH TWO SEPARATED－ELECTRODES

In this paper, an oscillation frequency equation for a pizoelectric sensor with two separated-electrodes is theoretically derived and experimentally verified. The correlatione of the oscillation frequency and the liquid properties are investigated.

Continuous frequency and phase spectrograms: a study of their 2D and 3D capabilities and application to musical signal analysis

A new lighting and enlargement on phase spectrogram （PS） and frequency spectrogram （FS） is presented in this paper. These representations result from the coupling of power spectrogram and short time Fourier transform （STFT）. The main contribution is the construction of the 3D phase spectrogram （3DPS） and the 3D frequency spectrogram （3DFS）. These new tools allow such specific test signals as small slope linear chirp, phase jump case of musical signal analysis is reported. The main objective is to and small frequency jump to be analyzed. An application detect small frequency and phase variations in order to characterize each type of sound attack without losing the amplitude information given by power spectrogram

Frequency Domain Filtering SAR Interferometric Phase Noise Using the Amended Matrix Pencil Model

Interferometric phase filtering is one of the key steps in interferometricsynthetic aperture radar (InSAR/SAR). However, the ideal filtering results are difficult toobtain due to dense fringe and low coherence regions. Moreover, the InSAR/SAR datarange is relatively large, so the efficiency of interferential phase filtering is one of themajor problems. In this letter, we proposed an interferometric phase filtering methodbased on an amended matrix pencil and linear window mean filter. The combination ofthe matrix pencil and the linear mean filter are introduced to the interferometric phasefiltering for the first time. First, the interferometric signal is analyzed, and theinterferometric phase filtering is transformed into a local frequency estimation problem.Then, the local frequency is estimated using an amended matrix pencil at a window. Thelocal frequency can represent terrain changes, thus suggesting that the frequency can beaccurately estimated even in dense fringe regions. Finally, the local frequency is filteredby using a linear window mean filter, and the filtered phase is recovered. The proposedmethod is calculated by some matrices. Therefore, the computational complexity isreduced, and the efficiency of the interferometric phase filtering is improved.Experiments are conducted with simulated and real InSAR data. The proposed methodexhibits a better filtering effect and an ideal efficiency as compared with the traditionalfiltering method.