Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing. The evaluation results are obtained by analyzing shut-in water hammer pre...Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing. The evaluation results are obtained by analyzing shut-in water hammer pressure signal. The field-sampled water hammer signal is often disturbed by noise interference. Noise interference exists in various pumping stages during water hammer diagnostics, with significantly different frequency range and energy distribution. Clarifying the differences in frequency range and energy distribution between effective water hammer signals and noise is the basis of setting specific filtering parameters, including filtering frequency range and energy thresholds. Filtering specifically could separate the effective signal and noise, which is the key to ensuring the accuracy of water hammer diagnosis. As an emerging technique, there is a lack of research on the frequency range and energy distribution of effective signals in water hammer diagnostics. In this paper, the frequency range and energy distribution characteristics of field-sampled water hammer signals were clarified quantitatively and qualitatively for the first time by a newly proposed comprehensive water hammer segmentation-energy analysis method. The water hammer signals were preprocessed and divided into three segments, including pre-shut-in, water hammer oscillation, and leak-off segment. Then, the three segments were analyzed by energy analysis and correlation analysis. The results indicated that, one aspect, the frequency range of water hammer oscillation spans from 0 to 0.65 Hz, considered as effective water hammer signal. The pre-shut-in and leak-off segment ranges from 0 to 0.35 Hz and 0-0.2 Hz respectively. Meanwhile, odd harmonics were manifested in water hammer oscillation segment, with the harmonic frequencies ranging approximately from 0.07 to 0.75 Hz. Whereas integer harmonics were observed in pre-shut-in segment, ranging from 6 to 40 Hz. The other aspect, the energy distribution of water hammer signals was analyzed in different frequency ranges. In 0-1 Hz, an exponential decay was observed in all three segments. In 1-100 Hz, a periodical energy distribution was observed in pre-shut-in segment, an exponential decay was observed in water hammer oscillation, and an even energy distribution was observed in leak-off segment. In 100-500 Hz, an even energy distribution was observed in those three segments, yet the highest magnitude was noted in leak-off segment. In this study, the effective frequency range and energy distribution characteristics of the field-sampled water hammer signals in different segments were sufficiently elucidated quantitatively and qualitatively for the first time, laying the groundwork for optimizing the filtering parameters of the field filtering models and advancing the accuracy of identifying downhole event locations.展开更多
Vibration detection using sensors with both wide working frequency range,good sensitivity,and other good performances is a topic of great interest in fields such as inertial navigation,deep-sea fishing boat engines co...Vibration detection using sensors with both wide working frequency range,good sensitivity,and other good performances is a topic of great interest in fields such as inertial navigation,deep-sea fishing boat engines condition monitoring,seismic monitoring,attitude,and heading reference system,etc.This paper investigates two 6H-SIC MEMS diaphragms,one triangular and the other square,used in a fiber optic Fabry–Perot(FP)accelerometer in an experimental scenario.The triangular chip shows a wide working frequency range of 630 Hz–5300 Hz,a natural frequency of 44.3 k Hz,and a mechanical sensitivity of 0.154 nm/g.An optimal structure of the square chip used in a probe such as a fiber optic FP accelerometer also shows a wide working frequency range of 120 Hz–2300 Hz;a good sensitivity of 31.5 m V/g,a resonance frequency of7873 Hz,an accuracy of 0.96%F.S.,a frequency measurement error of 1.15%,and an excellent linearity of 0.9995.展开更多
This paper reports on an evaluation of airborne sound insulation in a wider frequency range then is used in classical measurements. For analyzing sound insulation was used frequency range from 50 Hz to 10 kHz via stan...This paper reports on an evaluation of airborne sound insulation in a wider frequency range then is used in classical measurements. For analyzing sound insulation was used frequency range from 50 Hz to 10 kHz via standard range I00 Hz to 3,15 kHz. For four constructions with different structure was measured sound reduction index depend on frequency and calculated Weighted sound reduction index according to EN ISO 717-1. Then the results were compared. The measurements were made for samples of construction with different sizes. The results of measurements show how the size of sample influence on measured sound insulation. This article could be useful for specialist of architect acoustic and all who interest in sound insulation.展开更多
Two induction magnetometers have been installed at Zhongshan Station and Davis Station, Antarctica respectively. We adopt with cross-spectral analysis technique to analyze the data of the two induction magnetometers, ...Two induction magnetometers have been installed at Zhongshan Station and Davis Station, Antarctica respectively. We adopt with cross-spectral analysis technique to analyze the data of the two induction magnetometers, in June, September,December 1996 and March 1997. to investigate the Pc3 frequency range pulsation occurrence and propagation characteristics in the cusp latitudes. The results are summarized as following:At Zhongshan-Davis Stations, the Pc3 frequency range pulsations occur mainly around the local noon/ local magnetic noon and local magnetic midnight respectively. In daytime, the pulsations have a seasonal variation in amplitude, occurrence and temporal range, all of them are sma1lest in winter. But in nighttime, the pulsations have no such a variation. The pu1sation amplitude in nighttime is much larger than the one in daytime all oveI the year. The pulsation propagating direction is mainly western in daytime and irregularly in nighttime. It can be thought that the different sources of the pulsation and the ionospheric electric conductivity are mainly responsible for these characteristics.展开更多
In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a p...In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a plate-shaped absorber is given in this paper.In the example,the frequency of the full-size measurement ranges from 2.0 GHz to 2.4 GHz,the thickness of the full-size absorber is 1 mm and the scale ratio is 1/5.A two-layer scale absorber is obtained by the proposed method.The thickness values of the bottom and top layer are 0.4 mm and 0.5 mm,respectively.Furthermore,the scattering properties of a plate model and an SLICY model are studied by FEKO to verify the effectiveness of the designed scale absorber.Compared with the corresponding values from the theoretical scale model,the average values of the absolute deviations in 10 GHz～12 GHz are 0.53 d Bm^2,0.65 d Bm^2,0.76 d Bm^2 for the plate model and 0.20 d Bm^2,0.95 d Bm^2,0.77 d Bm^2 for the SLICY model while the incident angles are 0°,30°,and 60°,respectively.These deviations fall within the Radar cross section（RCS） measurement tolerance.Thus,the work in this paper has important theoretical and practical significance.展开更多
A novel toggled flip-flop（TFF） divide-by-two circuit（DTC） and its optimization method based on a large-signal analysis approach are proposed.By reducing the output RC constant in tracking mode and making it large ...A novel toggled flip-flop（TFF） divide-by-two circuit（DTC） and its optimization method based on a large-signal analysis approach are proposed.By reducing the output RC constant in tracking mode and making it large in latching mode,compressing the internal signal swing as well as compensating the current leaked in the latching mode, the operating frequency range is greatly expanded.Implemented in a SMIC 0.13μm RF CMOS process with a 1.2 V power supply,it can work under an ultra-wide frequency band ranging from 320 MHz to 29.6 GHz.Experimental results show that two phase-locked loops（PLLs） with the proposed DTC can achieve in-band phase noise of-94 dBc/Hz @ 10 kHz under 4224 MHz operating frequency and-84 dBc/Hz @ 10 kHz under 10 GHz operating frequency,respectively. The power consumption of the proposed DTC is reduced by almost 50%compared with the conventional counterparts.展开更多
An algorithm for the layout of a piezoelectric that provides the most efficient performance within a specified range of vibration frequencies is proposed in this paper.This algorithm is based on the consideration of a...An algorithm for the layout of a piezoelectric that provides the most efficient performance within a specified range of vibration frequencies is proposed in this paper.This algorithm is based on the consideration of a special parameter within the area of a piezoelectric element’s possible location.This parameter characterizes the superposition of electromechanical coupling coefficients’for all the natural vibration frequencies included in a specified frequency range.The condition for defining the best option for location of the piezoelectric element in the case of several equivalent positions is specified.The efficiency of the proposed algorithm is shown numerically.The electromechanical coupling coefficients were calculated numerically based on solution to the problem of natural vibrations for electroelastic bodies using a finite element method.The calculations were performed to define the best location for a single piezoelectric element at the surface of a thin-walled shell having a half-cylindrical shape.The results are presented for natural vibration frequencies within the frequency range from 0 up to 1100 Hz.The numerical results were obtained by solving the problem of natural vibrations with a finite element method using the ANSYS software package.展开更多
This paper considers the coupling analysis of phased antenna array designed to excite fast wave in the ion cyclotron range of frequency. The coupling of the antenna is calculated in slab geometry. The coupling code ba...This paper considers the coupling analysis of phased antenna array designed to excite fast wave in the ion cyclotron range of frequency. The coupling of the antenna is calculated in slab geometry. The coupling code based on the variational principle gives the self-consistent current flowing in the antenna, this method has been extended so that it can be applied to a phased antenna array. As an example, this paper analyses the coupling prosperities of a 2 × 2 phased antenna array. It gives the optimum geometry of antenna array. The fields excited at plasma surface are found to more or less correspond to the antenna current phasing.展开更多
-Theoretical form of equilibrium range is given on the basis of the wind wave frequency spectra proposed by Wenel al. (1988a,b,c, 1989a,b). The effects of peakness factor and water depth are discussed. In the case of ...-Theoretical form of equilibrium range is given on the basis of the wind wave frequency spectra proposed by Wenel al. (1988a,b,c, 1989a,b). The effects of peakness factor and water depth are discussed. In the case of deep water the e-quilibrium range is reduced to the form first proposed by Toba (1973) and the coefficient of the formula is shown to be the function of nondimensional fetch or peak frequency. Results of the present paper have been verified through field data.展开更多
It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of ...It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.展开更多
The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of ...The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.展开更多
Radio Frequency (RF) switch circuit is the basic part of microwave devices and systems. The non-linearity distortion figure is necessary in the field of large dynamic range of signal. This letter analyzes the basic sw...Radio Frequency (RF) switch circuit is the basic part of microwave devices and systems. The non-linearity distortion figure is necessary in the field of large dynamic range of signal. This letter analyzes the basic switch circuit and its inter-modulation, and studies in detail the measurement methods and systems of RF switch intercept point. It has provided cascaded simulation testing methods, which can accurately measure the PF switch, of which the second or third order intercept point value is above 75dB and 60dB, respectively. As the testing results are consistent with the theoretical analyses, it proves that the validity of the method satisfies the requirements of large scaled linearity measurement in engineering.展开更多
Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing.However,the interaction between different spectra and matter varies significan...Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing.However,the interaction between different spectra and matter varies significantly,making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities.We designed a modulator based on a planar nested multiscale metasurface,incorporating silicon(Si)and perovskite as control materials,to modulate both microwave and terahertz(THz)ranges.展开更多
The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effe...The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effectively resolves the three-dimensional(3D)geometry and the electromagnetic field using the finite element method.Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases,surface current density on the antenna straps,and background plasma density.Notably,the non-uniform surface current density on the antenna straps,resulting from the presence of induced currents,contributes to a reduction in coupling power within the edge plasma.Furthermore,the calculated coupling impedance increases with plasma density,corroborating well with experimental measurements.展开更多
Controlled nuclear fusion represents a significant solution for future clean energy,with ion cyclotron range of frequency(ICRF)heating emerging as one of the most promising technologies for heating the fusion plasma.T...Controlled nuclear fusion represents a significant solution for future clean energy,with ion cyclotron range of frequency(ICRF)heating emerging as one of the most promising technologies for heating the fusion plasma.This study primarily presents a self-developed 2D ion cyclotron resonance antenna electromagnetic field solver(ICRAEMS)code implemented on the MATLAB platform,which solves the electric field wave equation by using the finite element method,establishing perfectly matched layer(PML)boundary conditions,and post-processing the electromagnetic field data.This code can be utilized to facilitate the design and optimization processes of antennas for ICRF heating technology.Furthermore,this study examines the electric field distribution and power spectrum associated with various antenna phases to investigate how different antenna configurations affect the electromagnetic field propagation and coupling characteristics.展开更多
A wide range fractional-N frequency synthesizer in 0.18μm RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency ran...A wide range fractional-N frequency synthesizer in 0.18μm RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency range.A 16-bit third-order sigma-delta modulator with dither is used to randomize the fractional spur. The active area is 0.6 mm;.The experimental results show the proposed frequency synthesizer consumes 4.3 raA from a single 1.8 V supply voltage except for buffers.The frequency range is 1.44-2.11 GHz and the frequency resolution is less than 0.4 kHz.The phase noise is -94 dBc/Hz @ 100 kHz and -121 dBc/Hz @ 1 MHz at the output of the prescaler with a loop bandwidth of approximately 120 kHz.The performance meets the requirements for the multi-band and multi-mode transceiver applications.展开更多
A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses...A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission re- sponses and the Mach-Zehnder interferometers （MZIs）, this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a freauencv ranee from 0.1 to 5.3 GHz.展开更多
In this paper, a novel Voltage-Controlled Oscillator （VCO） using the harmonic control circuit based on the quad-band Composite Right/Left-Handed （CRLH） Transmission Line （TL） is presented to reduce the phase noi...In this paper, a novel Voltage-Controlled Oscillator （VCO） using the harmonic control circuit based on the quad-band Composite Right/Left-Handed （CRLH） Transmission Line （TL） is presented to reduce the phase noise without the reduction of the frequeacy tuning range and miniaturizing the circuit size. The phase noise has been reduced by the quad-band harmonic control circuit which has the short impedance for the second- and third- and fourth- and fifth-hannonic components. The CRLH TL with two Left-Handed （LH） （backward） and two Right-Handed （RH） （forward） pass bands are used to design the quad-band harmonic control circuit. The high- Q resonator has been used to reduce the phase noise, but it has the problem of the frequency timing range reduction. However, the frequency tuning range of the proposed VCO has not reduced because the phase noise has reduced without the high-Q resonator. The miniaturization of the circuit size is achieved by using the quad-band CRLH TL instead of the conventional RH TL, The phase noise of VCO is - 124.43～ - 122.67 dBc/Hz at 100 kHz in the tuning range of 5. 729 ～5.934 GHz.展开更多
Through analyzing the influence on echo signal by factors of kinematical parameters of airborne SAR platform and radar antenna direction, this letter, on the basis of classical SAR echo signal analogue algorithm, puts...Through analyzing the influence on echo signal by factors of kinematical parameters of airborne SAR platform and radar antenna direction, this letter, on the basis of classical SAR echo signal analogue algorithm, puts forward certain airborne SAR echo signal analogue algorithm of distance directional frequency domain pulse coherent accumulation, and goes through simulation. The simulation results have proved the effectiveness of this algorithm.展开更多
基金support from the National Natural Science Foundation of China(No.52374019).
文摘Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing. The evaluation results are obtained by analyzing shut-in water hammer pressure signal. The field-sampled water hammer signal is often disturbed by noise interference. Noise interference exists in various pumping stages during water hammer diagnostics, with significantly different frequency range and energy distribution. Clarifying the differences in frequency range and energy distribution between effective water hammer signals and noise is the basis of setting specific filtering parameters, including filtering frequency range and energy thresholds. Filtering specifically could separate the effective signal and noise, which is the key to ensuring the accuracy of water hammer diagnosis. As an emerging technique, there is a lack of research on the frequency range and energy distribution of effective signals in water hammer diagnostics. In this paper, the frequency range and energy distribution characteristics of field-sampled water hammer signals were clarified quantitatively and qualitatively for the first time by a newly proposed comprehensive water hammer segmentation-energy analysis method. The water hammer signals were preprocessed and divided into three segments, including pre-shut-in, water hammer oscillation, and leak-off segment. Then, the three segments were analyzed by energy analysis and correlation analysis. The results indicated that, one aspect, the frequency range of water hammer oscillation spans from 0 to 0.65 Hz, considered as effective water hammer signal. The pre-shut-in and leak-off segment ranges from 0 to 0.35 Hz and 0-0.2 Hz respectively. Meanwhile, odd harmonics were manifested in water hammer oscillation segment, with the harmonic frequencies ranging approximately from 0.07 to 0.75 Hz. Whereas integer harmonics were observed in pre-shut-in segment, ranging from 6 to 40 Hz. The other aspect, the energy distribution of water hammer signals was analyzed in different frequency ranges. In 0-1 Hz, an exponential decay was observed in all three segments. In 1-100 Hz, a periodical energy distribution was observed in pre-shut-in segment, an exponential decay was observed in water hammer oscillation, and an even energy distribution was observed in leak-off segment. In 100-500 Hz, an even energy distribution was observed in those three segments, yet the highest magnitude was noted in leak-off segment. In this study, the effective frequency range and energy distribution characteristics of the field-sampled water hammer signals in different segments were sufficiently elucidated quantitatively and qualitatively for the first time, laying the groundwork for optimizing the filtering parameters of the field filtering models and advancing the accuracy of identifying downhole event locations.
基金Project supported by the National Natural Science Foundation of China(Grant No.32473216)Ningbo Youth Science and Technology Innovation Leading Talent Project(Grant No.2023QL004)。
文摘Vibration detection using sensors with both wide working frequency range,good sensitivity,and other good performances is a topic of great interest in fields such as inertial navigation,deep-sea fishing boat engines condition monitoring,seismic monitoring,attitude,and heading reference system,etc.This paper investigates two 6H-SIC MEMS diaphragms,one triangular and the other square,used in a fiber optic Fabry–Perot(FP)accelerometer in an experimental scenario.The triangular chip shows a wide working frequency range of 630 Hz–5300 Hz,a natural frequency of 44.3 k Hz,and a mechanical sensitivity of 0.154 nm/g.An optimal structure of the square chip used in a probe such as a fiber optic FP accelerometer also shows a wide working frequency range of 120 Hz–2300 Hz;a good sensitivity of 31.5 m V/g,a resonance frequency of7873 Hz,an accuracy of 0.96%F.S.,a frequency measurement error of 1.15%,and an excellent linearity of 0.9995.
文摘This paper reports on an evaluation of airborne sound insulation in a wider frequency range then is used in classical measurements. For analyzing sound insulation was used frequency range from 50 Hz to 10 kHz via standard range I00 Hz to 3,15 kHz. For four constructions with different structure was measured sound reduction index depend on frequency and calculated Weighted sound reduction index according to EN ISO 717-1. Then the results were compared. The measurements were made for samples of construction with different sizes. The results of measurements show how the size of sample influence on measured sound insulation. This article could be useful for specialist of architect acoustic and all who interest in sound insulation.
文摘Two induction magnetometers have been installed at Zhongshan Station and Davis Station, Antarctica respectively. We adopt with cross-spectral analysis technique to analyze the data of the two induction magnetometers, in June, September,December 1996 and March 1997. to investigate the Pc3 frequency range pulsation occurrence and propagation characteristics in the cusp latitudes. The results are summarized as following:At Zhongshan-Davis Stations, the Pc3 frequency range pulsations occur mainly around the local noon/ local magnetic noon and local magnetic midnight respectively. In daytime, the pulsations have a seasonal variation in amplitude, occurrence and temporal range, all of them are sma1lest in winter. But in nighttime, the pulsations have no such a variation. The pu1sation amplitude in nighttime is much larger than the one in daytime all oveI the year. The pulsation propagating direction is mainly western in daytime and irregularly in nighttime. It can be thought that the different sources of the pulsation and the ionospheric electric conductivity are mainly responsible for these characteristics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61601299 and 11404213)the Shanghai Municipal Science and Technology Commission,China(Grant Nos.17210730900 and 15ZR1439600)the Defense Industrial Technology,China(Grant No.B2120132001)
文摘In order to design the scale model in a wide frequency range,a method based on the reflective loss is proposed according to the high-frequency approximation algorithm,and an example of designing the scale model of a plate-shaped absorber is given in this paper.In the example,the frequency of the full-size measurement ranges from 2.0 GHz to 2.4 GHz,the thickness of the full-size absorber is 1 mm and the scale ratio is 1/5.A two-layer scale absorber is obtained by the proposed method.The thickness values of the bottom and top layer are 0.4 mm and 0.5 mm,respectively.Furthermore,the scattering properties of a plate model and an SLICY model are studied by FEKO to verify the effectiveness of the designed scale absorber.Compared with the corresponding values from the theoretical scale model,the average values of the absolute deviations in 10 GHz～12 GHz are 0.53 d Bm^2,0.65 d Bm^2,0.76 d Bm^2 for the plate model and 0.20 d Bm^2,0.95 d Bm^2,0.77 d Bm^2 for the SLICY model while the incident angles are 0°,30°,and 60°,respectively.These deviations fall within the Radar cross section（RCS） measurement tolerance.Thus,the work in this paper has important theoretical and practical significance.
基金Project supported by the National High Technology Research and Development Program of China(No.SQ2008AA01Z4473469)
文摘A novel toggled flip-flop（TFF） divide-by-two circuit（DTC） and its optimization method based on a large-signal analysis approach are proposed.By reducing the output RC constant in tracking mode and making it large in latching mode,compressing the internal signal swing as well as compensating the current leaked in the latching mode, the operating frequency range is greatly expanded.Implemented in a SMIC 0.13μm RF CMOS process with a 1.2 V power supply,it can work under an ultra-wide frequency band ranging from 320 MHz to 29.6 GHz.Experimental results show that two phase-locked loops（PLLs） with the proposed DTC can achieve in-band phase noise of-94 dBc/Hz @ 10 kHz under 4224 MHz operating frequency and-84 dBc/Hz @ 10 kHz under 10 GHz operating frequency,respectively. The power consumption of the proposed DTC is reduced by almost 50%compared with the conventional counterparts.
基金supported by the Russian Foundation for Basic Research[18-31-00080 mol_a].
文摘An algorithm for the layout of a piezoelectric that provides the most efficient performance within a specified range of vibration frequencies is proposed in this paper.This algorithm is based on the consideration of a special parameter within the area of a piezoelectric element’s possible location.This parameter characterizes the superposition of electromechanical coupling coefficients’for all the natural vibration frequencies included in a specified frequency range.The condition for defining the best option for location of the piezoelectric element in the case of several equivalent positions is specified.The efficiency of the proposed algorithm is shown numerically.The electromechanical coupling coefficients were calculated numerically based on solution to the problem of natural vibrations for electroelastic bodies using a finite element method.The calculations were performed to define the best location for a single piezoelectric element at the surface of a thin-walled shell having a half-cylindrical shape.The results are presented for natural vibration frequencies within the frequency range from 0 up to 1100 Hz.The numerical results were obtained by solving the problem of natural vibrations with a finite element method using the ANSYS software package.
文摘This paper considers the coupling analysis of phased antenna array designed to excite fast wave in the ion cyclotron range of frequency. The coupling of the antenna is calculated in slab geometry. The coupling code based on the variational principle gives the self-consistent current flowing in the antenna, this method has been extended so that it can be applied to a phased antenna array. As an example, this paper analyses the coupling prosperities of a 2 × 2 phased antenna array. It gives the optimum geometry of antenna array. The fields excited at plasma surface are found to more or less correspond to the antenna current phasing.
文摘-Theoretical form of equilibrium range is given on the basis of the wind wave frequency spectra proposed by Wenel al. (1988a,b,c, 1989a,b). The effects of peakness factor and water depth are discussed. In the case of deep water the e-quilibrium range is reduced to the form first proposed by Toba (1973) and the coefficient of the formula is shown to be the function of nondimensional fetch or peak frequency. Results of the present paper have been verified through field data.
基金supported by the Wuhan Applied Basic Research Project,China(Grant No.20140101010009)the National Natural Science Foundation of China(Grant Nos.61405063,61475054,11574105,and 61177095)+1 种基金the Hubei Science and Technology Agency Project,China(Grant No.2015BCE052)the Fundamental Research Funds for the Central Universities,China(Grant No.2017KFYXJJ029)
文摘It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.
基金supported by the National Natural Science Foundation of China(Nos.61179018,61102165,61002006,61102167)Aeronautical Science Foundation of China(No.20115584006)Special Foundation Program for Mountain Tai Scholars
文摘The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.
文摘Radio Frequency (RF) switch circuit is the basic part of microwave devices and systems. The non-linearity distortion figure is necessary in the field of large dynamic range of signal. This letter analyzes the basic switch circuit and its inter-modulation, and studies in detail the measurement methods and systems of RF switch intercept point. It has provided cascaded simulation testing methods, which can accurately measure the PF switch, of which the second or third order intercept point value is above 75dB and 60dB, respectively. As the testing results are consistent with the theoretical analyses, it proves that the validity of the method satisfies the requirements of large scaled linearity measurement in engineering.
基金National Natural Science Foundation of China(61975046,62375068)。
文摘Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing.However,the interaction between different spectra and matter varies significantly,making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities.We designed a modulator based on a planar nested multiscale metasurface,incorporating silicon(Si)and perovskite as control materials,to modulate both microwave and terahertz(THz)ranges.
基金Project supported by the National MCF Energy Research and Development Program(Grant No.2022YFE03190100)the National Natural Science Foundation of China(Grant Nos.12422513,12105035,and U21A20438)the Xiaomi Young Talents Program。
文摘The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effectively resolves the three-dimensional(3D)geometry and the electromagnetic field using the finite element method.Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases,surface current density on the antenna straps,and background plasma density.Notably,the non-uniform surface current density on the antenna straps,resulting from the presence of induced currents,contributes to a reduction in coupling power within the edge plasma.Furthermore,the calculated coupling impedance increases with plasma density,corroborating well with experimental measurements.
基金Project supported by the National MCF Energy R&D Program(Grant No.2022YFE03190100)the National Natural Science Foundation of China(Grant Nos.12422513,12105035,and U21A20438)the Xiaomi Young Talents Program.
文摘Controlled nuclear fusion represents a significant solution for future clean energy,with ion cyclotron range of frequency(ICRF)heating emerging as one of the most promising technologies for heating the fusion plasma.This study primarily presents a self-developed 2D ion cyclotron resonance antenna electromagnetic field solver(ICRAEMS)code implemented on the MATLAB platform,which solves the electric field wave equation by using the finite element method,establishing perfectly matched layer(PML)boundary conditions,and post-processing the electromagnetic field data.This code can be utilized to facilitate the design and optimization processes of antennas for ICRF heating technology.Furthermore,this study examines the electric field distribution and power spectrum associated with various antenna phases to investigate how different antenna configurations affect the electromagnetic field propagation and coupling characteristics.
文摘A wide range fractional-N frequency synthesizer in 0.18μm RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency range.A 16-bit third-order sigma-delta modulator with dither is used to randomize the fractional spur. The active area is 0.6 mm;.The experimental results show the proposed frequency synthesizer consumes 4.3 raA from a single 1.8 V supply voltage except for buffers.The frequency range is 1.44-2.11 GHz and the frequency resolution is less than 0.4 kHz.The phase noise is -94 dBc/Hz @ 100 kHz and -121 dBc/Hz @ 1 MHz at the output of the prescaler with a loop bandwidth of approximately 120 kHz.The performance meets the requirements for the multi-band and multi-mode transceiver applications.
基金supported by the National "973" Program of China(No.2012CB315705)the National "863" Program of China(No.2011AA010306)+2 种基金the National Natural Science Foundation of China(Nos.61107058,61120106001,60932004,61001121,and 60837004)the Beijing Excellent Doctoral Thesis Project(No.YB20101001301)the Cooperation Project between the Province and Ministries(No.2011A090200025)
文摘A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmis- sion responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission re- sponses and the Mach-Zehnder interferometers （MZIs）, this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a freauencv ranee from 0.1 to 5.3 GHz.
文摘In this paper, a novel Voltage-Controlled Oscillator （VCO） using the harmonic control circuit based on the quad-band Composite Right/Left-Handed （CRLH） Transmission Line （TL） is presented to reduce the phase noise without the reduction of the frequeacy tuning range and miniaturizing the circuit size. The phase noise has been reduced by the quad-band harmonic control circuit which has the short impedance for the second- and third- and fourth- and fifth-hannonic components. The CRLH TL with two Left-Handed （LH） （backward） and two Right-Handed （RH） （forward） pass bands are used to design the quad-band harmonic control circuit. The high- Q resonator has been used to reduce the phase noise, but it has the problem of the frequency timing range reduction. However, the frequency tuning range of the proposed VCO has not reduced because the phase noise has reduced without the high-Q resonator. The miniaturization of the circuit size is achieved by using the quad-band CRLH TL instead of the conventional RH TL, The phase noise of VCO is - 124.43～ - 122.67 dBc/Hz at 100 kHz in the tuning range of 5. 729 ～5.934 GHz.
文摘Through analyzing the influence on echo signal by factors of kinematical parameters of airborne SAR platform and radar antenna direction, this letter, on the basis of classical SAR echo signal analogue algorithm, puts forward certain airborne SAR echo signal analogue algorithm of distance directional frequency domain pulse coherent accumulation, and goes through simulation. The simulation results have proved the effectiveness of this algorithm.
