A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new ...A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new demodulation method can complete the demodulation of the FSK signals only with the carrier frequency and without any carrier phase information. The simulation results show that the performance of anti-noise of the new method is better than that of the incoherent demodulation method and the fluctuation of the carrier phase has little effect on the new method. So the new demodulation method has a fine prospect in the practical applications.展开更多
The real-time monitoring of fracture propagation during hydraulic fracturing is crucial for obtaining a deeper understanding of fracture morphology and optimizing hydraulic fracture designs.Accurate measurements of ke...The real-time monitoring of fracture propagation during hydraulic fracturing is crucial for obtaining a deeper understanding of fracture morphology and optimizing hydraulic fracture designs.Accurate measurements of key fracture parameters,such as the fracture height and width,are particularly important to ensure efficient oilfield development and precise fracture diagnosis.This study utilized the optical frequency domain reflectometer(OFDR)technique in physical simulation experiments to monitor fractures during indoor true triaxial hydraulic fracturing experiments.The results indicate that the distributed fiber optic strain monitoring technology can efficiently capture the initiation and expansion of fractures.In horizontal well monitoring,the fiber strain waterfall plot can be used to interpret the fracture width,initiation location,and expansion speed.The fiber response can be divided into three stages:strain contraction convergence,strain band formation,and postshutdown strain rate reversal.When the fracture does not contact the fiber,a dual peak strain phenomenon occurs in the fiber and gradually converges as the fracture approaches.During vertical well monitoring in adjacent wells,within the effective monitoring range of the fiber,the axial strain produced by the fiber can represent the fracture height with an accuracy of 95.6%relative to the actual fracture height.This study provides a new perspective on real-time fracture monitoring.The response patterns of fiber-induced strain due to fractures can help us better understand and assess the dynamic fracture behavior,offering significant value for the optimization of oilfield development and fracture diagnostic techniques.展开更多
This paper presents a compact ultra-low-power phase-locked loop (PLL) based binary phase-shift keying(BPSK)demodulator. The loop-filter-less(LPF-less) PLL is proposed to make phase of PLL output carrier signal track t...This paper presents a compact ultra-low-power phase-locked loop (PLL) based binary phase-shift keying(BPSK)demodulator. The loop-filter-less(LPF-less) PLL is proposed to make phase of PLL output carrier signal track the phase of BPSK signal in real time. Thus, the maximum date rate can be significantly extended to the half of the carrier frequency(f_(carrier)) with a very compact size compared to prior PLL-based BPSK demodulators. Furthermore, eliminating all the static power in our LPF-less PLL, the energy efficiency is obviously improved. Fabricated in a 40-nm CMOS process, our prototype occupies 0.0012-mm^(2)core active area, and achieves the maximum data rate of 6.78 Mb/s (f_(carrier)/2) at f_(carrier)of 13.56 MHz. The power consumption and energy efficiency is 4.47 μW and 0.66 pJ/bit at 6.78-Mb/s data rate, respectively.展开更多
Aiming at the problem that the bit error rate(BER)of asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)space optical communication system is significantly affected by different turbule...Aiming at the problem that the bit error rate(BER)of asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)space optical communication system is significantly affected by different turbulence intensities,the deep learning technique is proposed to the polarization code decoding in ACO-OFDM space optical communication system.Moreover,this system realizes the polarization code decoding and signal demodulation without frequency conduction with superior performance and robustness compared with the performance of traditional decoder.Simulations under different turbulence intensities as well as different mapping orders show that the convolutional neural network(CNN)decoder trained under weak-medium-strong turbulence atmospheric channels achieves a performance improvement of about 10^(2)compared to the conventional decoder at 4-quadrature amplitude modulation(4QAM),and the BERs for both 16QAM and 64QAM are in between those of the conventional decoder.展开更多
The principle of optical time-domain reflection localization limits the sensing spatial resolution of Raman distributed optical fiber sensing.We provide a solution for a Raman distributed optical fiber sensing system ...The principle of optical time-domain reflection localization limits the sensing spatial resolution of Raman distributed optical fiber sensing.We provide a solution for a Raman distributed optical fiber sensing system with kilometer-level sensing distance and submeter spatial resolution.Based on this,we propose a Raman distributed optical fiber sensing scheme based on chaotic pulse cluster demodulation.Chaotic pulse clusters are used as the probe signal,in preference to conventional pulsed or chaotic single-pulse lasers.Furthermore,the accurate positioning of the temperature variety region along the sensing fiber can be realized using chaotic pulse clusters.The proposed demodulation scheme can enhance the signal-to-noise ratio by improving the correlation between the chaotic reference and the chaotic Raman anti-Stokes scattering signals.The experiment achieved a sensing spatial resolution of 30 cm at a distributed temperature-sensing distance of∼6.0 km.Furthermore,we explored the influence of chaotic pulse width and detector bandwidth on the sensing spatial resolution.In addition,the theoretical experiments proved that the sensing spatial resolution in the proposed scheme was independent of the pulse width and sensing distance.展开更多
Recently, the rapid progress of quantum sensing research reveals that Rydberg atoms have great potential in becoming high-precision centimeter-scale antennas for low-frequency fields. In order to facilitate efficient ...Recently, the rapid progress of quantum sensing research reveals that Rydberg atoms have great potential in becoming high-precision centimeter-scale antennas for low-frequency fields. In order to facilitate efficient and reliable detection of low-frequency fields via Rydberg atoms, we designed and implemented a heterodyne method based on the linear response to external signals under the condition of Rydberg electromagnetically induced transparency(EIT). Instead of relying on observing changes in the absorption of light by Rydberg atoms, our method focuses on the phase modulation effect on the probe laser induced by low-frequency fields via the Rydberg EIT mechanism and utilizes a special demodulation process to accurately retrieve signals including both amplitude and phase. The general principles of our method apply to both electric and magnetic fields, and it is even possible to realize a combination of both functionalities in the same apparatus. In particular, we experimentally demonstrate the full cycle of operations with respect to both cases. In measuring low-frequency electric fields,we discover that the Rydberg dipole–dipole interaction among atoms induces a linear superposition of Rydberg states with different angular momentum, generating a first-order response corresponding to the signature of the linear Stark effect. As Rydberg atoms have excellent coupling strengths with electric fields, our results indicate that our method can hopefully achieve high-precision performance for practical tasks in the future.展开更多
This paper introduces a novel digital transceiver for the cordless telephone zero （CT0） standard,which uses a digital modulation and demodulation technique to handle the signal instead of the traditional analog meth...This paper introduces a novel digital transceiver for the cordless telephone zero （CT0） standard,which uses a digital modulation and demodulation technique to handle the signal instead of the traditional analog meth-od. In the transmitter,a fractional-N phase locked loop （PLL） is utilized to realize the continuous phase frequency shift key （CPFSK） modulation,and a 2 Ts raised cosine （2RC） shaping technique is used to reduce the occupied bandwidth. In the receiver,a novel digital method is proposed to demodulate the 2RC CPFSK signal. This chip is fabricated using an SMIC 0.35μm mixed signal CMOS process with a die size of 2mm × 2mm. With an external low noise amplifier （LNA）,the sensitivity of the chip is better than -103dBm.展开更多
We report a low power ASK IF receiver for short-range wireless systems,which includes an AGC loop that compensates the channel attenuation and an ASK detector. A novel current-limited transconductor and feed-forward d...We report a low power ASK IF receiver for short-range wireless systems,which includes an AGC loop that compensates the channel attenuation and an ASK detector. A novel current-limited transconductor and feed-forward differential peak detector have been designed to maintain a high compression ratio and fast response for the AGC with lower power consumption. A storage unit with a zero and a feed-forward structure have been introduced into the peak detector to control the damping characteristic of the AGC loop. A rectifier and low-pass filter included in the ASK detector have been integrated into a more compact structure to further lower the power consumption. The simulation results show the feasibility of the proposed technique.展开更多
A hardwale demodulation method for 2-D edge detection is proposed. The filtering step and the differential step are implemented by using the hardware circuit. This demodulation circuit simplifies the edgefinder and re...A hardwale demodulation method for 2-D edge detection is proposed. The filtering step and the differential step are implemented by using the hardware circuit. This demodulation circuit simplifies the edgefinder and reduces the measuring cycle. The calibration method of scale setting is also presented,and bymeasuring some calibrated objects,the demodulation errors and the error correction table is obtained.展开更多
A single-chip DVB-C quadrature amplitude modulation（QAM） demodulator is proposed,which integrates a 3.3V 10bit 40MSPS analog-to-digital converter and a forward error correction decoder. The demodulator chip can supp...A single-chip DVB-C quadrature amplitude modulation（QAM） demodulator is proposed,which integrates a 3.3V 10bit 40MSPS analog-to-digital converter and a forward error correction decoder. The demodulator chip can support 4-256 QAM with variable bit rate up to 80Mbps. It features a wide carrier offset acquisition range,optimal demodulation algorithm,and small circuit area. The chip is implemented in SMIC 0.25μm 1P5M mixed-signal CMOS technology with a die size of 3.5mm×3. 5mm. The maximum power consumption is 447mW.展开更多
A nondestructive continuous instrumented wheelset design is proposed based on strain gauges placing inside of the wheel web and wireless telemetry system. The signal feature analysis including frequency contents and h...A nondestructive continuous instrumented wheelset design is proposed based on strain gauges placing inside of the wheel web and wireless telemetry system. The signal feature analysis including frequency contents and high order harmonic ripples is also carried out. The strain gradient decoupling method for vertical and lateral force identification is proposed based on the strain distributions under respective loads. The method implements minimum crosstalk effects and insensitive to the varying contact points. The KMT telemetry system is adopted for wireless inductive powering and signal transferring. The drilling holes on the wheel and axles are avoidable to ensure the integrity and long-term using of the wheelset. Bridging and demodulating schemes for lateral and vertical force are designed respectively as they have dramatic differences at the dynamic signal features. High order harmonic ripple analysis and error estimation are gotten by independent waveforms. Based on the data form calibration test rig, it is indicated that the high order ripple amplitudes are below 10% of the demodulation amplitudes and fulfill designed requirements.展开更多
Phase-sensitive optical time-domain reflectometry(Φ-OTDR)has attracted numerous attention due to its superior performance in detecting the weak perturbations along the fiber.Relying on the ultra-sensitivity of light ...Phase-sensitive optical time-domain reflectometry(Φ-OTDR)has attracted numerous attention due to its superior performance in detecting the weak perturbations along the fiber.Relying on the ultra-sensitivity of light phase to the tiny deformation of optical fiber,Φ-OTDR has been treated as a powerful technique with a wide range of applications.It is fundamental to extract the phase of scattering light wave accurately and the methods include coherent detection,I/Q demodulation,3 by 3 coupler,dual probe pulses,and so on.Meanwhile,researchers have also made great efforts to improve the performance ofΦ-OTDR.The frequency response range,the measurement accuracy,the sensing distance,the spatial resolution,and the accuracy of event discrimination,all have been enhanced by various techniques.Furthermore,lots of researches on the applications in various kinds of fields have been carried out,where certain modifications and techniques have been developed.Therefore,Φ-OTDR remains as a booming technique in both researches and applications.展开更多
To increase the storage capacity in holographic data storage(HDS),the information to be stored is encoded into a complex amplitude.Fast and accurate retrieval of amplitude and phase from the reconstructed beam is nece...To increase the storage capacity in holographic data storage(HDS),the information to be stored is encoded into a complex amplitude.Fast and accurate retrieval of amplitude and phase from the reconstructed beam is necessary during data readout in HDS.In this study,we proposed a complex amplitude demodulation method based on deep learning from a single-shot diffraction intensity image and verified it by a non-interferometric lensless experiment demodulating four-level amplitude and four-level phase.By analyzing the correlation between the diffraction intensity features and the amplitude and phase encoding data pages,the inverse problem was decomposed into two backward operators denoted by two convolutional neural networks(CNNs)to demodulate amplitude and phase respectively.The experimental system is simple,stable,and robust,and it only needs a single diffraction image to realize the direct demodulation of both amplitude and phase.To our investigation,this is the first time in HDS that multilevel complex amplitude demodulation is achieved experimentally from one diffraction intensity image without iterations.展开更多
It is a challenging issue to detect bearing fault under nonstationary conditions and gear noise interferences. Meanwhile, the application of the traditional methods is limited by their deficiencies in the aspect of co...It is a challenging issue to detect bearing fault under nonstationary conditions and gear noise interferences. Meanwhile, the application of the traditional methods is limited by their deficiencies in the aspect of computational accuracy and e ciency, or dependence on the tachometer. Hence, a new fault diagnosis strategy is proposed to remove gear interferences and spectrum smearing phenomenon without the tachometer and angular resampling technique. In this method, the instantaneous dominant meshing multiple(IDMM) is firstly extracted from the time-frequency representation(TFR) of the raw signal, which can be used to calculate the phase functions(PF) and the frequency points(FP). Next, the resonance frequency band excited by the faulty bearing is obtained by the band-pass filter. Furthermore, based on the PFs, the generalized demodulation transform(GDT) is applied to the envelope of the filtered signal. Finally, the target bearing is diagnosed by matching the peaks in the spectra of demodulated signals with the theoretical FPs. The analysis results of simulated and experimental signal demonstrate that the proposed method is an e ective and reliable tool for bearing fault diagnosis without the tachometer and the angular resampling.展开更多
Condition monitoring and fault diagnosis of gearboxes play an important role in the maintenance of mechanical systems.The vibration signal of gearboxes is characterized by complex spectral structure and strong time va...Condition monitoring and fault diagnosis of gearboxes play an important role in the maintenance of mechanical systems.The vibration signal of gearboxes is characterized by complex spectral structure and strong time variability,which brings challenges to fault feature extraction.To address this issue,a new demodulation technique,based on the Fourier decomposition method and resonance demodulation,is proposed to extract fault-related information.First,the Fourier decomposition method decomposes the vibration signal into Fourier intrinsic band functions(FIBFs)adaptively in the frequency domain.Then,the original signal is segmented into short-time vectors to construct double-row matrices and the maximum singular value ratio method is employed to estimate the resonance frequency.Then,the resonance frequency is used as a criterion to guide the selection of the most relevant FIBF for demodulation analysis.Finally,for the optimal FIBF,envelope demodulation is conducted to identify the fault characteristic frequency.The main contributions are that the proposed method describes how to obtain the resonance frequency effectively and how to select the optimal FIBF after decomposition in order to extract the fault characteristic frequency.Both numerical and experimental studies are conducted to investigate the performance of the proposed method.It is demonstrated that the proposed method can effectively demodulate the fault information from the original signal.展开更多
A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with saw...A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm-1 575 nm,and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.展开更多
Although envelope spectrum does not involve complicated sideband,thus has a much simpler structure than the common Fourier spectrum,it is still subject to the efect of planets passing or time variant vibration transfe...Although envelope spectrum does not involve complicated sideband,thus has a much simpler structure than the common Fourier spectrum,it is still subject to the efect of planets passing or time variant vibration transfer pams.The presence of planets passing frequency,sun gear rotating frequency,or planet carrier rotating frequency in the envelope spectrum may confuse the analysis in fault diagnosis.Therefore,it is important to look for an approach to remove the interferences caused by the efect of planets passing or time variant vibration transfer paths.展开更多
A displacement sensor based on the fiber Fabry-Perot (F-P) cavity was proposed in this paper. Theoretical and experimental analyses were presented. Displacement resolution was demonstrated by spectrum-domain experimen...A displacement sensor based on the fiber Fabry-Perot (F-P) cavity was proposed in this paper. Theoretical and experimental analyses were presented. Displacement resolution was demonstrated by spectrum-domain experiments to obtain the dynamic range of the F-P sensor, and a piezoelectric crystal unit (PZT) was used as the driver. The output signal was modulated by a piezoelectric ceramic ring and demodulated by a phase-locked oscillator. The experimental results show that the displacement resolution of the F-P sensor is less than 5 nm and the dynamic range is more than 100 μm. As acceleration is the second-order differential of displacement, an accelerometer model was proposed using the finite element method (FEM) nd ANSYS software.展开更多
基金the National Natural Science Foundation of China (60272077) the Science Foundation of Aeronautics (02F53030).
文摘A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new demodulation method can complete the demodulation of the FSK signals only with the carrier frequency and without any carrier phase information. The simulation results show that the performance of anti-noise of the new method is better than that of the incoherent demodulation method and the fluctuation of the carrier phase has little effect on the new method. So the new demodulation method has a fine prospect in the practical applications.
基金supported by the National Natural Science Foundation of China(Grant No.52104060)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2021QE015).
文摘The real-time monitoring of fracture propagation during hydraulic fracturing is crucial for obtaining a deeper understanding of fracture morphology and optimizing hydraulic fracture designs.Accurate measurements of key fracture parameters,such as the fracture height and width,are particularly important to ensure efficient oilfield development and precise fracture diagnosis.This study utilized the optical frequency domain reflectometer(OFDR)technique in physical simulation experiments to monitor fractures during indoor true triaxial hydraulic fracturing experiments.The results indicate that the distributed fiber optic strain monitoring technology can efficiently capture the initiation and expansion of fractures.In horizontal well monitoring,the fiber strain waterfall plot can be used to interpret the fracture width,initiation location,and expansion speed.The fiber response can be divided into three stages:strain contraction convergence,strain band formation,and postshutdown strain rate reversal.When the fracture does not contact the fiber,a dual peak strain phenomenon occurs in the fiber and gradually converges as the fracture approaches.During vertical well monitoring in adjacent wells,within the effective monitoring range of the fiber,the axial strain produced by the fiber can represent the fracture height with an accuracy of 95.6%relative to the actual fracture height.This study provides a new perspective on real-time fracture monitoring.The response patterns of fiber-induced strain due to fractures can help us better understand and assess the dynamic fracture behavior,offering significant value for the optimization of oilfield development and fracture diagnostic techniques.
基金supported by the National Natural Science Foundation of China under grant 62222409 and 62174153by Key Research Program of Frontier Sciences, CAS, under grant ZDBS-LY-JSC008。
文摘This paper presents a compact ultra-low-power phase-locked loop (PLL) based binary phase-shift keying(BPSK)demodulator. The loop-filter-less(LPF-less) PLL is proposed to make phase of PLL output carrier signal track the phase of BPSK signal in real time. Thus, the maximum date rate can be significantly extended to the half of the carrier frequency(f_(carrier)) with a very compact size compared to prior PLL-based BPSK demodulators. Furthermore, eliminating all the static power in our LPF-less PLL, the energy efficiency is obviously improved. Fabricated in a 40-nm CMOS process, our prototype occupies 0.0012-mm^(2)core active area, and achieves the maximum data rate of 6.78 Mb/s (f_(carrier)/2) at f_(carrier)of 13.56 MHz. The power consumption and energy efficiency is 4.47 μW and 0.66 pJ/bit at 6.78-Mb/s data rate, respectively.
基金supported by the National Natural Science Foundation of China(No.12104141).
文摘Aiming at the problem that the bit error rate(BER)of asymmetrically clipped optical orthogonal frequency division multiplexing(ACO-OFDM)space optical communication system is significantly affected by different turbulence intensities,the deep learning technique is proposed to the polarization code decoding in ACO-OFDM space optical communication system.Moreover,this system realizes the polarization code decoding and signal demodulation without frequency conduction with superior performance and robustness compared with the performance of traditional decoder.Simulations under different turbulence intensities as well as different mapping orders show that the convolutional neural network(CNN)decoder trained under weak-medium-strong turbulence atmospheric channels achieves a performance improvement of about 10^(2)compared to the conventional decoder at 4-quadrature amplitude modulation(4QAM),and the BERs for both 16QAM and 64QAM are in between those of the conventional decoder.
基金supported by the National Natural Science Foundation of China(Grant Nos.U23A20375 and 62075151)the National Key Research and Development Program of China(Grant No.202103021223042).
文摘The principle of optical time-domain reflection localization limits the sensing spatial resolution of Raman distributed optical fiber sensing.We provide a solution for a Raman distributed optical fiber sensing system with kilometer-level sensing distance and submeter spatial resolution.Based on this,we propose a Raman distributed optical fiber sensing scheme based on chaotic pulse cluster demodulation.Chaotic pulse clusters are used as the probe signal,in preference to conventional pulsed or chaotic single-pulse lasers.Furthermore,the accurate positioning of the temperature variety region along the sensing fiber can be realized using chaotic pulse clusters.The proposed demodulation scheme can enhance the signal-to-noise ratio by improving the correlation between the chaotic reference and the chaotic Raman anti-Stokes scattering signals.The experiment achieved a sensing spatial resolution of 30 cm at a distributed temperature-sensing distance of∼6.0 km.Furthermore,we explored the influence of chaotic pulse width and detector bandwidth on the sensing spatial resolution.In addition,the theoretical experiments proved that the sensing spatial resolution in the proposed scheme was independent of the pulse width and sensing distance.
基金supported by the Science and Technology Commission of Shanghai Municipality (Grant No.24DP2600202)the National Key R&D Program of China (Grant No.2024YFB4504002)+2 种基金Industrial Technology Development Research Program of Shanghai Institute of Optics and Fine Mechanicsthe National Natural Science Foundation of China (Grant No.92165107)the China Postdoctoral Science Foundation (Grant Nos.2024M753359 for S.J.and2022M723270 for X.W.)。
文摘Recently, the rapid progress of quantum sensing research reveals that Rydberg atoms have great potential in becoming high-precision centimeter-scale antennas for low-frequency fields. In order to facilitate efficient and reliable detection of low-frequency fields via Rydberg atoms, we designed and implemented a heterodyne method based on the linear response to external signals under the condition of Rydberg electromagnetically induced transparency(EIT). Instead of relying on observing changes in the absorption of light by Rydberg atoms, our method focuses on the phase modulation effect on the probe laser induced by low-frequency fields via the Rydberg EIT mechanism and utilizes a special demodulation process to accurately retrieve signals including both amplitude and phase. The general principles of our method apply to both electric and magnetic fields, and it is even possible to realize a combination of both functionalities in the same apparatus. In particular, we experimentally demonstrate the full cycle of operations with respect to both cases. In measuring low-frequency electric fields,we discover that the Rydberg dipole–dipole interaction among atoms induces a linear superposition of Rydberg states with different angular momentum, generating a first-order response corresponding to the signature of the linear Stark effect. As Rydberg atoms have excellent coupling strengths with electric fields, our results indicate that our method can hopefully achieve high-precision performance for practical tasks in the future.
文摘This paper introduces a novel digital transceiver for the cordless telephone zero （CT0） standard,which uses a digital modulation and demodulation technique to handle the signal instead of the traditional analog meth-od. In the transmitter,a fractional-N phase locked loop （PLL） is utilized to realize the continuous phase frequency shift key （CPFSK） modulation,and a 2 Ts raised cosine （2RC） shaping technique is used to reduce the occupied bandwidth. In the receiver,a novel digital method is proposed to demodulate the 2RC CPFSK signal. This chip is fabricated using an SMIC 0.35μm mixed signal CMOS process with a die size of 2mm × 2mm. With an external low noise amplifier （LNA）,the sensitivity of the chip is better than -103dBm.
文摘We report a low power ASK IF receiver for short-range wireless systems,which includes an AGC loop that compensates the channel attenuation and an ASK detector. A novel current-limited transconductor and feed-forward differential peak detector have been designed to maintain a high compression ratio and fast response for the AGC with lower power consumption. A storage unit with a zero and a feed-forward structure have been introduced into the peak detector to control the damping characteristic of the AGC loop. A rectifier and low-pass filter included in the ASK detector have been integrated into a more compact structure to further lower the power consumption. The simulation results show the feasibility of the proposed technique.
文摘A hardwale demodulation method for 2-D edge detection is proposed. The filtering step and the differential step are implemented by using the hardware circuit. This demodulation circuit simplifies the edgefinder and reduces the measuring cycle. The calibration method of scale setting is also presented,and bymeasuring some calibrated objects,the demodulation errors and the error correction table is obtained.
文摘A single-chip DVB-C quadrature amplitude modulation（QAM） demodulator is proposed,which integrates a 3.3V 10bit 40MSPS analog-to-digital converter and a forward error correction decoder. The demodulator chip can support 4-256 QAM with variable bit rate up to 80Mbps. It features a wide carrier offset acquisition range,optimal demodulation algorithm,and small circuit area. The chip is implemented in SMIC 0.25μm 1P5M mixed-signal CMOS technology with a die size of 3.5mm×3. 5mm. The maximum power consumption is 447mW.
文摘A nondestructive continuous instrumented wheelset design is proposed based on strain gauges placing inside of the wheel web and wireless telemetry system. The signal feature analysis including frequency contents and high order harmonic ripples is also carried out. The strain gradient decoupling method for vertical and lateral force identification is proposed based on the strain distributions under respective loads. The method implements minimum crosstalk effects and insensitive to the varying contact points. The KMT telemetry system is adopted for wireless inductive powering and signal transferring. The drilling holes on the wheel and axles are avoidable to ensure the integrity and long-term using of the wheelset. Bridging and demodulating schemes for lateral and vertical force are designed respectively as they have dramatic differences at the dynamic signal features. High order harmonic ripple analysis and error estimation are gotten by independent waveforms. Based on the data form calibration test rig, it is indicated that the high order ripple amplitudes are below 10% of the demodulation amplitudes and fulfill designed requirements.
基金supported in part by the Startup Fund from Southern University of Science and Technology and Shenzhen government under Grant No.Y01236128by the National Natural Science Foundation of China(NSFC)under Grant Nos.61627816 and 61975076by the Qing Lan Project of Jiangsu Province。
文摘Phase-sensitive optical time-domain reflectometry(Φ-OTDR)has attracted numerous attention due to its superior performance in detecting the weak perturbations along the fiber.Relying on the ultra-sensitivity of light phase to the tiny deformation of optical fiber,Φ-OTDR has been treated as a powerful technique with a wide range of applications.It is fundamental to extract the phase of scattering light wave accurately and the methods include coherent detection,I/Q demodulation,3 by 3 coupler,dual probe pulses,and so on.Meanwhile,researchers have also made great efforts to improve the performance ofΦ-OTDR.The frequency response range,the measurement accuracy,the sensing distance,the spatial resolution,and the accuracy of event discrimination,all have been enhanced by various techniques.Furthermore,lots of researches on the applications in various kinds of fields have been carried out,where certain modifications and techniques have been developed.Therefore,Φ-OTDR remains as a booming technique in both researches and applications.
基金We are grateful for financial supports from National Key Research and Development Program of China(2018YFA0701800)Project of Fujian Province Major Science and Technology(2020HZ01012)+1 种基金Natural Science Foundation of Fujian Province(2021J01160)National Natural Science Foundation of China(62061136005).
文摘To increase the storage capacity in holographic data storage(HDS),the information to be stored is encoded into a complex amplitude.Fast and accurate retrieval of amplitude and phase from the reconstructed beam is necessary during data readout in HDS.In this study,we proposed a complex amplitude demodulation method based on deep learning from a single-shot diffraction intensity image and verified it by a non-interferometric lensless experiment demodulating four-level amplitude and four-level phase.By analyzing the correlation between the diffraction intensity features and the amplitude and phase encoding data pages,the inverse problem was decomposed into two backward operators denoted by two convolutional neural networks(CNNs)to demodulate amplitude and phase respectively.The experimental system is simple,stable,and robust,and it only needs a single diffraction image to realize the direct demodulation of both amplitude and phase.To our investigation,this is the first time in HDS that multilevel complex amplitude demodulation is achieved experimentally from one diffraction intensity image without iterations.
基金Supported by National Natural Science Foundation of China(Grant Nos.51335006 and 51605244)
文摘It is a challenging issue to detect bearing fault under nonstationary conditions and gear noise interferences. Meanwhile, the application of the traditional methods is limited by their deficiencies in the aspect of computational accuracy and e ciency, or dependence on the tachometer. Hence, a new fault diagnosis strategy is proposed to remove gear interferences and spectrum smearing phenomenon without the tachometer and angular resampling technique. In this method, the instantaneous dominant meshing multiple(IDMM) is firstly extracted from the time-frequency representation(TFR) of the raw signal, which can be used to calculate the phase functions(PF) and the frequency points(FP). Next, the resonance frequency band excited by the faulty bearing is obtained by the band-pass filter. Furthermore, based on the PFs, the generalized demodulation transform(GDT) is applied to the envelope of the filtered signal. Finally, the target bearing is diagnosed by matching the peaks in the spectra of demodulated signals with the theoretical FPs. The analysis results of simulated and experimental signal demonstrate that the proposed method is an e ective and reliable tool for bearing fault diagnosis without the tachometer and the angular resampling.
基金supported by the National Key R&D Program of China(No.2019YFB2004604)the National Natural Science Foundation of China(No.52075477)the Key R&D Program of Zhejiang Province(No.2021C01139),China。
文摘Condition monitoring and fault diagnosis of gearboxes play an important role in the maintenance of mechanical systems.The vibration signal of gearboxes is characterized by complex spectral structure and strong time variability,which brings challenges to fault feature extraction.To address this issue,a new demodulation technique,based on the Fourier decomposition method and resonance demodulation,is proposed to extract fault-related information.First,the Fourier decomposition method decomposes the vibration signal into Fourier intrinsic band functions(FIBFs)adaptively in the frequency domain.Then,the original signal is segmented into short-time vectors to construct double-row matrices and the maximum singular value ratio method is employed to estimate the resonance frequency.Then,the resonance frequency is used as a criterion to guide the selection of the most relevant FIBF for demodulation analysis.Finally,for the optimal FIBF,envelope demodulation is conducted to identify the fault characteristic frequency.The main contributions are that the proposed method describes how to obtain the resonance frequency effectively and how to select the optimal FIBF after decomposition in order to extract the fault characteristic frequency.Both numerical and experimental studies are conducted to investigate the performance of the proposed method.It is demonstrated that the proposed method can effectively demodulate the fault information from the original signal.
基金Doctoral Foundation of Ministry of Education of China (No. 20040056008)
文摘A discrimination measurement method and demodulation technique for fiber Bragg grating (FBG) sensors were presented using digital filtering technique. The system can control a tunable fiber Fabry-Perot filter with sawtooth wave voltage generated by digital clock to interrogate FBG sensors. Using the analogue digital converter (ADC), the reflected FBG signals were sampled with synchronous digital clock. With the aid of digital matched filtering technique, the sampled FBG signals were processed to obtain the maximum signal-to-noise ratio (SNR) and the Bragg wavelength shift from the FBG signals was recovered. The results demonstrate that this system has a scanning range of 1 520 nm-1 575 nm,and the wavelength detection accuracy is less than 2 pm with 1.5 Hz scanning frequency.
文摘Although envelope spectrum does not involve complicated sideband,thus has a much simpler structure than the common Fourier spectrum,it is still subject to the efect of planets passing or time variant vibration transfer pams.The presence of planets passing frequency,sun gear rotating frequency,or planet carrier rotating frequency in the envelope spectrum may confuse the analysis in fault diagnosis.Therefore,it is important to look for an approach to remove the interferences caused by the efect of planets passing or time variant vibration transfer paths.
基金Project (No. 111303-8112D2) supported by the National DefenseResearch Foundation of Zhejiang University, China
文摘A displacement sensor based on the fiber Fabry-Perot (F-P) cavity was proposed in this paper. Theoretical and experimental analyses were presented. Displacement resolution was demonstrated by spectrum-domain experiments to obtain the dynamic range of the F-P sensor, and a piezoelectric crystal unit (PZT) was used as the driver. The output signal was modulated by a piezoelectric ceramic ring and demodulated by a phase-locked oscillator. The experimental results show that the displacement resolution of the F-P sensor is less than 5 nm and the dynamic range is more than 100 μm. As acceleration is the second-order differential of displacement, an accelerometer model was proposed using the finite element method (FEM) nd ANSYS software.
