Aiming at the application background of sliding spotlight mode Synthetic Aperture Radar (SAR) ima... more Aiming at the application background of sliding spotlight mode Synthetic Aperture Radar (SAR) imaging processing, this paper builds a System-on-a-Programmable-Chip-based (SoPC-based) sliding spotlight mode SAR imaging verification system, which uses software and hardware collaborative design method to complete algorithm-to-hardware mapping and can quickly and truly perform in FPGA or ASIC. Finally, we analyzed the implementation of the imaging prototype system and the imaging results. For the generation of correlation factors, this paper hierarchically decomposes the factor generation operation to realize the time division multiplexing of the operation unit, in order to reduce resource consumption. At the same time, a variable point Fast Fourier Transformation (FFT) processor based on a variable radix-23 multiplexing butterfly unit is designed and implemented. Combining these two parts with other modules enables the entire sliding spotlight mode imaging process. On the basis of keeping the error of the result small, the overall resource consumption is greatly reduced. The 1024~32768 point FFT is implemented by the top-level configurable method, and the operation delay is reduced by more than 20% compared with the Xilinx FFT IP core. The final imaging time is reduced to seconds, and the imaging results meet the requirements. Subsequent compatibility design for other SAR imaging modes also can be achieved.
For the chirp scaling algorithm of synthetic aperture radar imaging, an efficient transmission of... more For the chirp scaling algorithm of synthetic aperture radar imaging, an efficient transmission of a large volume of data is indispensable. Prior to imaging, there is a requirement for appropriate pre-processing of the echo signal by digital down conversion (DDC). The DDC module has to remove the carrier, having an appropriate filtering processing and down-sampling processing. No matter what imaging mode is chosen, such as the stripmap mode, spotlight mode, and sliding spotlight, the needs of the whole imaging system are matched by setting a series of configurations about this pre-processing module and this transmission module. The system-on-a-programmable-chip constituted by the Advanced RISC Machine and field programmable gate array (FPGA) is the perfect experimental platform to test the performance of this system. Some of the algorithms, which are more feasible for this specific project for pre-processing in Maltab, were transplanted to FPGA using the VHSIC Hardware Description Language for functional verification. Finally, the processing results in Matlab were compared with this system to find the difference. At the same time, the time that elapsed from the 2 GB original data entering the system to the time the processed results were completely returned to the PC was also counted.
Medical & Biological Engineering & Computing, Jul 11, 2017
Recovery of heart rate variability after treadmill exercise analyzed by lagged Recovery of heart ... more Recovery of heart rate variability after treadmill exercise analyzed by lagged Recovery of heart rate variability after treadmill exercise analyzed by lagged Poincaré plot and spectral characteristics Poincaré plot and spectral characteristics PLEASE CITE THE PUBLISHED VERSION
Journal of the University of Shanghai for Science and Technology, 2008
Under two body-postures (supine and 45° reclining) the blood pulse signal on toe was detected via... more Under two body-postures (supine and 45° reclining) the blood pulse signal on toe was detected via non-invasive photoplethysmography technique while the lower limb was passively raised in different height. The regulations of blood pulse volume and lower limb height were found and their relation was described through curves in figures.
Monitoring of mixed venous oxygen saturation (SvO(2)) is currently performed using invasive fibre... more Monitoring of mixed venous oxygen saturation (SvO(2)) is currently performed using invasive fibre-optic catheters. This procedure is not without risk as complications may arise from catheterization. This paper describes an alternative, non-invasive method of monitoring peripheral venous oxygen saturation (SxvO(2)) which, although it cannot replace pulmonary artery catheters, can serve as an adjunct/early warning indicator of when there is an imbalance in oxygen supply and demand. The technique requires the generation of an artificial venous pulse at the finger, thereby causing modulation of the venous blood volume within the digit. The blood volume changes are monitored using an optical sensor. Just as pulse oximetry utilizes the natural arterial pulse to perform a spectrophotometric analysis of the peripheral blood in order to estimate the arterial blood oxygen saturation, the proposed venous oximetry technique uses the artificially generated venous pulse to estimate SxvO(2). A prototype device was tested in a pilot study with patients undergoing heart surgery. Data from this study support the notion that the method is capable of tracking haemodynamic changes and suggests the technique is worthy of further development and evaluation.
2019 IEEE International Conference on Signal, Information and Data Processing (ICSIDP), Dec 1, 2019
In the multi-mode SAR imaging processing targeted in this paper, the FFT requirement granularity ... more In the multi-mode SAR imaging processing targeted in this paper, the FFT requirement granularity ranges from 1024 to 32768. Therefore, this paper mainly describes the method of implementing reconfigurable and variable-level FFT units using radix-2k, By analyzing and comparing the radix 2k algorithm, the radix-23 is selected as the basis of the single-channel FFT butterfly, and the range of the point representation is extended by the butterfly transformation downward compatible with the radix-22/radix-2. This paper realizes an architecture of the single channel delay feedback variable-point, high precision FFT processor.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
We study the dependence of total secondary electron yield (SEY) of micro-porous silver surface on... more We study the dependence of total secondary electron yield (SEY) of micro-porous silver surface on incident angle of primary electron. First, we produce regular and random micro-porous surfaces on silver plated aluminium samples by photolithography pattern process and direct chemical etching method, respectively. Second, we study the dependence of the SEY characteristics of these surfaces on the primary electron incident angle from 0° to 60°. The experimental results show that micro-porous surface with large porosity can suppress SEY effectively either for normal incidence or oblique incidence. The maximum SEY of the directly chemical etched sample can reach a 45% reduction relative to the original flat sample. We also show the anomalous experimental phenomenon that the SEY of directly chemical etched sample with large porosity does not increase with incident angle. Third, we explain the complicated SEY dependence on incident angle qualitatively by the secondary electron trapping effect in micro-pores as well as the Monte Carlo simulation based on phenomenological model of secondary electron emission. Finally, we suggest a third order polynomial formula to describe the SEY dependence on incident angle which will be useful in particle simulation. In total, we demonstrate that micro-porous surface with large porosity is effective in SEY suppression under both normal and oblique incidence and thus the proposed direct chemical etching method is prospective in related areas such as multipactor improvement.
A little explored area of human activity recognition (HAR) is in people operating in relation to ... more A little explored area of human activity recognition (HAR) is in people operating in relation to extreme environments, e.g., mountaineers. In these contexts, the ability to accurately identify activities, alongside other data streams, has the potential to prevent death and serious negative health events to the operators. This study aimed to address this user group and investigate factors associated with the placement, number, and combination of accelerometer sensors. Eight participants (age = 25.0 ± 7 years) wore 17 accelerometers simultaneously during lab-based simulated mountaineering activities, under a range of equipment and loading conditions. Initially, a selection of machine learning techniques was tested. Secondly, a comprehensive analysis of all possible combinations of the 17 accelerometers was performed to identify the optimum number of sensors, and their respective body locations. Finally, the impact of activity-specific equipment on the classifier accuracy was explored....
2022 IEEE International Conference on E-health Networking, Application & Services (HealthCom)
Quality photoplethysmographic (PPG) signals are essential for accurate physiological assessment. ... more Quality photoplethysmographic (PPG) signals are essential for accurate physiological assessment. However, the PPG acquisition process is often accompanied by spurious motion artefacts (MAs), especially during medium-high intensity physical activity. This study proposes a generative adversarial network (PPG-GAN) to create de-noised versions of measure PPG signals. The Adaptive Notch Filtration (ANF) algorithm, which enables the extraction of accurate heart rates (HR) and respiration rates (RR) from PPG signals, is used as the approximate reference signal to train the PPG-GAN. The generated PPG signals from test inputs provide a heart rate (HR) with a mean absolute error of 1.68 bpm for the IEEE-SPC dataset. A comparison with goldstandard HR and RR measurements, for our in-house dataset, show the errors in absolute value of less than 5%. The generated PPG signals, for the test clips, show a very strong correlation with their reference values, R ≈ 0.98. The results suggest that PPG-GAN could be a paradigm for MA-free PPG signal processing specifically for personal healthcare, even during high intensity activity.
Optical Diagnostics and Sensing XVIII: Toward Point-of-Care Diagnostics, Feb 20, 2018
To effectively capture human vital signs, a multi-wavelength optoelectronic patch sensor (MOEPS),... more To effectively capture human vital signs, a multi-wavelength optoelectronic patch sensor (MOEPS), together with a schematic architecture of electronics, was developed to overcome the drawbacks of present photoplethysmographic (PPG) sensors. To obtain a better performance of in vivo physiological measurement, the optimal illuminations, i.e., light emitting diodes (LEDs) in the MOEPS, whose wavelength is automatically adjusted to each specific subject, were selected to capture better PPG signals. A multiplexed electronic architecture has been well established to properly drive the MOEPS and effectively capture pulsatile waveforms at rest. The protocol was designed to investigate its performance with the participation of 11 healthy subjects aged between 18 and 30. The signals obtained from green (525nm) and orange (595nm) illuminations were used to extract heart rate (HR) and oxygen saturation (SpO 2 %). These results were compared with data, simultaneously acquired, from a commercial ECG and a pulse oximeter. Considering the difficulty for current devices to attain the SpO 2 %, a new computing method, to obtain the value of SpO 2 %, is proposed depended on the green and orange wavelength illuminations. The values of SpO 2 % between the MOEPS and the commercial Pulse Oximeter devics showed that the results were in good agreement. The values of HR showed close correlation between commercial devices and the MOEPS (HR: r 1 =0.994(Green); r 2 =0.992(Orange); r 3 =0.975(Red); r 4 =0.990(IR)).
Biophotonics: Photonic Solutions for Better Health Care V, 2016
Non-contact imaging photoplethysmography (iPPG) to detect pulsatile blood microcirculation in tis... more Non-contact imaging photoplethysmography (iPPG) to detect pulsatile blood microcirculation in tissue has been selected as a successor to low spatial resolution and slow scanning blood perfusion techniques currently employed by clinicians. The proposed iPPG system employs a novel illumination source constructed of multiple high power LEDs with narrow spectral emission, which are temporally modulated and synchronised with a high performance sCMOS sensor. To ensure spectrum stability and prevent thermal wavelength drift due to junction temperature variations, each LED features a custom-designed thermal management system to effectively dissipate generated heat and auto-adjust current flow. The use of a multi-wavelength approach has resulted in simultaneous microvascular perfusion monitoring at various tissue depths, which is an added benefit for specific clinical applications. A synchronous detection algorithm to extract weak photoplethysmographic pulse-waveforms demonstrated robustness and high efficiency when applied to even small regions of 5 mm 2. The experimental results showed evidences that the proposed system could achieve noticeable accuracy in blood perfusion monitoring by creating complex amplitude and phase maps for the tissue under examination.
We study secondary electron yield (SEY) suppression for metal materials using a roughened surface... more We study secondary electron yield (SEY) suppression for metal materials using a roughened surface with a micro-porous array. First, we perform a Monte Carlo simulation of the electron trajectory in a single cylindrical well using a phenomenological model of secondary electron emission and the SEY suppression efficiency of a micro-porous array. The simulation results show that the SEY of a roughened surface is affected significantly by the aspect ratio of the micro-pores and the surface porosity of the metal plate. Then, to verify the simulation results, we produce a micro-porous array on metal plates using photolithography and measure their SEYs. We show that the micro-porous array structure can efficiently suppress the SEY of metal materials, and the measurements agree quantitatively with the corresponding simulation results. Finally, we derive an analytical formula to evaluate easily the SEY suppression efficiency of the Ag micro-porous array. In total, the micro-porous array prop...
Aiming at the application background of sliding spotlight mode Synthetic Aperture Radar (SAR) ima... more Aiming at the application background of sliding spotlight mode Synthetic Aperture Radar (SAR) imaging processing, this paper builds a System-on-a-Programmable-Chip-based (SoPC-based) sliding spotlight mode SAR imaging verification system, which uses software and hardware collaborative design method to complete algorithm-to-hardware mapping and can quickly and truly perform in FPGA or ASIC. Finally, we analyzed the implementation of the imaging prototype system and the imaging results. For the generation of correlation factors, this paper hierarchically decomposes the factor generation operation to realize the time division multiplexing of the operation unit, in order to reduce resource consumption. At the same time, a variable point Fast Fourier Transformation (FFT) processor based on a variable radix-23 multiplexing butterfly unit is designed and implemented. Combining these two parts with other modules enables the entire sliding spotlight mode imaging process. On the basis of keeping the error of the result small, the overall resource consumption is greatly reduced. The 1024~32768 point FFT is implemented by the top-level configurable method, and the operation delay is reduced by more than 20% compared with the Xilinx FFT IP core. The final imaging time is reduced to seconds, and the imaging results meet the requirements. Subsequent compatibility design for other SAR imaging modes also can be achieved.
For the chirp scaling algorithm of synthetic aperture radar imaging, an efficient transmission of... more For the chirp scaling algorithm of synthetic aperture radar imaging, an efficient transmission of a large volume of data is indispensable. Prior to imaging, there is a requirement for appropriate pre-processing of the echo signal by digital down conversion (DDC). The DDC module has to remove the carrier, having an appropriate filtering processing and down-sampling processing. No matter what imaging mode is chosen, such as the stripmap mode, spotlight mode, and sliding spotlight, the needs of the whole imaging system are matched by setting a series of configurations about this pre-processing module and this transmission module. The system-on-a-programmable-chip constituted by the Advanced RISC Machine and field programmable gate array (FPGA) is the perfect experimental platform to test the performance of this system. Some of the algorithms, which are more feasible for this specific project for pre-processing in Maltab, were transplanted to FPGA using the VHSIC Hardware Description Language for functional verification. Finally, the processing results in Matlab were compared with this system to find the difference. At the same time, the time that elapsed from the 2 GB original data entering the system to the time the processed results were completely returned to the PC was also counted.
Medical & Biological Engineering & Computing, Jul 11, 2017
Recovery of heart rate variability after treadmill exercise analyzed by lagged Recovery of heart ... more Recovery of heart rate variability after treadmill exercise analyzed by lagged Recovery of heart rate variability after treadmill exercise analyzed by lagged Poincaré plot and spectral characteristics Poincaré plot and spectral characteristics PLEASE CITE THE PUBLISHED VERSION
Journal of the University of Shanghai for Science and Technology, 2008
Under two body-postures (supine and 45° reclining) the blood pulse signal on toe was detected via... more Under two body-postures (supine and 45° reclining) the blood pulse signal on toe was detected via non-invasive photoplethysmography technique while the lower limb was passively raised in different height. The regulations of blood pulse volume and lower limb height were found and their relation was described through curves in figures.
Monitoring of mixed venous oxygen saturation (SvO(2)) is currently performed using invasive fibre... more Monitoring of mixed venous oxygen saturation (SvO(2)) is currently performed using invasive fibre-optic catheters. This procedure is not without risk as complications may arise from catheterization. This paper describes an alternative, non-invasive method of monitoring peripheral venous oxygen saturation (SxvO(2)) which, although it cannot replace pulmonary artery catheters, can serve as an adjunct/early warning indicator of when there is an imbalance in oxygen supply and demand. The technique requires the generation of an artificial venous pulse at the finger, thereby causing modulation of the venous blood volume within the digit. The blood volume changes are monitored using an optical sensor. Just as pulse oximetry utilizes the natural arterial pulse to perform a spectrophotometric analysis of the peripheral blood in order to estimate the arterial blood oxygen saturation, the proposed venous oximetry technique uses the artificially generated venous pulse to estimate SxvO(2). A prototype device was tested in a pilot study with patients undergoing heart surgery. Data from this study support the notion that the method is capable of tracking haemodynamic changes and suggests the technique is worthy of further development and evaluation.
2019 IEEE International Conference on Signal, Information and Data Processing (ICSIDP), Dec 1, 2019
In the multi-mode SAR imaging processing targeted in this paper, the FFT requirement granularity ... more In the multi-mode SAR imaging processing targeted in this paper, the FFT requirement granularity ranges from 1024 to 32768. Therefore, this paper mainly describes the method of implementing reconfigurable and variable-level FFT units using radix-2k, By analyzing and comparing the radix 2k algorithm, the radix-23 is selected as the basis of the single-channel FFT butterfly, and the range of the point representation is extended by the butterfly transformation downward compatible with the radix-22/radix-2. This paper realizes an architecture of the single channel delay feedback variable-point, high precision FFT processor.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
We study the dependence of total secondary electron yield (SEY) of micro-porous silver surface on... more We study the dependence of total secondary electron yield (SEY) of micro-porous silver surface on incident angle of primary electron. First, we produce regular and random micro-porous surfaces on silver plated aluminium samples by photolithography pattern process and direct chemical etching method, respectively. Second, we study the dependence of the SEY characteristics of these surfaces on the primary electron incident angle from 0° to 60°. The experimental results show that micro-porous surface with large porosity can suppress SEY effectively either for normal incidence or oblique incidence. The maximum SEY of the directly chemical etched sample can reach a 45% reduction relative to the original flat sample. We also show the anomalous experimental phenomenon that the SEY of directly chemical etched sample with large porosity does not increase with incident angle. Third, we explain the complicated SEY dependence on incident angle qualitatively by the secondary electron trapping effect in micro-pores as well as the Monte Carlo simulation based on phenomenological model of secondary electron emission. Finally, we suggest a third order polynomial formula to describe the SEY dependence on incident angle which will be useful in particle simulation. In total, we demonstrate that micro-porous surface with large porosity is effective in SEY suppression under both normal and oblique incidence and thus the proposed direct chemical etching method is prospective in related areas such as multipactor improvement.
A little explored area of human activity recognition (HAR) is in people operating in relation to ... more A little explored area of human activity recognition (HAR) is in people operating in relation to extreme environments, e.g., mountaineers. In these contexts, the ability to accurately identify activities, alongside other data streams, has the potential to prevent death and serious negative health events to the operators. This study aimed to address this user group and investigate factors associated with the placement, number, and combination of accelerometer sensors. Eight participants (age = 25.0 ± 7 years) wore 17 accelerometers simultaneously during lab-based simulated mountaineering activities, under a range of equipment and loading conditions. Initially, a selection of machine learning techniques was tested. Secondly, a comprehensive analysis of all possible combinations of the 17 accelerometers was performed to identify the optimum number of sensors, and their respective body locations. Finally, the impact of activity-specific equipment on the classifier accuracy was explored....
2022 IEEE International Conference on E-health Networking, Application & Services (HealthCom)
Quality photoplethysmographic (PPG) signals are essential for accurate physiological assessment. ... more Quality photoplethysmographic (PPG) signals are essential for accurate physiological assessment. However, the PPG acquisition process is often accompanied by spurious motion artefacts (MAs), especially during medium-high intensity physical activity. This study proposes a generative adversarial network (PPG-GAN) to create de-noised versions of measure PPG signals. The Adaptive Notch Filtration (ANF) algorithm, which enables the extraction of accurate heart rates (HR) and respiration rates (RR) from PPG signals, is used as the approximate reference signal to train the PPG-GAN. The generated PPG signals from test inputs provide a heart rate (HR) with a mean absolute error of 1.68 bpm for the IEEE-SPC dataset. A comparison with goldstandard HR and RR measurements, for our in-house dataset, show the errors in absolute value of less than 5%. The generated PPG signals, for the test clips, show a very strong correlation with their reference values, R ≈ 0.98. The results suggest that PPG-GAN could be a paradigm for MA-free PPG signal processing specifically for personal healthcare, even during high intensity activity.
Optical Diagnostics and Sensing XVIII: Toward Point-of-Care Diagnostics, Feb 20, 2018
To effectively capture human vital signs, a multi-wavelength optoelectronic patch sensor (MOEPS),... more To effectively capture human vital signs, a multi-wavelength optoelectronic patch sensor (MOEPS), together with a schematic architecture of electronics, was developed to overcome the drawbacks of present photoplethysmographic (PPG) sensors. To obtain a better performance of in vivo physiological measurement, the optimal illuminations, i.e., light emitting diodes (LEDs) in the MOEPS, whose wavelength is automatically adjusted to each specific subject, were selected to capture better PPG signals. A multiplexed electronic architecture has been well established to properly drive the MOEPS and effectively capture pulsatile waveforms at rest. The protocol was designed to investigate its performance with the participation of 11 healthy subjects aged between 18 and 30. The signals obtained from green (525nm) and orange (595nm) illuminations were used to extract heart rate (HR) and oxygen saturation (SpO 2 %). These results were compared with data, simultaneously acquired, from a commercial ECG and a pulse oximeter. Considering the difficulty for current devices to attain the SpO 2 %, a new computing method, to obtain the value of SpO 2 %, is proposed depended on the green and orange wavelength illuminations. The values of SpO 2 % between the MOEPS and the commercial Pulse Oximeter devics showed that the results were in good agreement. The values of HR showed close correlation between commercial devices and the MOEPS (HR: r 1 =0.994(Green); r 2 =0.992(Orange); r 3 =0.975(Red); r 4 =0.990(IR)).
Biophotonics: Photonic Solutions for Better Health Care V, 2016
Non-contact imaging photoplethysmography (iPPG) to detect pulsatile blood microcirculation in tis... more Non-contact imaging photoplethysmography (iPPG) to detect pulsatile blood microcirculation in tissue has been selected as a successor to low spatial resolution and slow scanning blood perfusion techniques currently employed by clinicians. The proposed iPPG system employs a novel illumination source constructed of multiple high power LEDs with narrow spectral emission, which are temporally modulated and synchronised with a high performance sCMOS sensor. To ensure spectrum stability and prevent thermal wavelength drift due to junction temperature variations, each LED features a custom-designed thermal management system to effectively dissipate generated heat and auto-adjust current flow. The use of a multi-wavelength approach has resulted in simultaneous microvascular perfusion monitoring at various tissue depths, which is an added benefit for specific clinical applications. A synchronous detection algorithm to extract weak photoplethysmographic pulse-waveforms demonstrated robustness and high efficiency when applied to even small regions of 5 mm 2. The experimental results showed evidences that the proposed system could achieve noticeable accuracy in blood perfusion monitoring by creating complex amplitude and phase maps for the tissue under examination.
We study secondary electron yield (SEY) suppression for metal materials using a roughened surface... more We study secondary electron yield (SEY) suppression for metal materials using a roughened surface with a micro-porous array. First, we perform a Monte Carlo simulation of the electron trajectory in a single cylindrical well using a phenomenological model of secondary electron emission and the SEY suppression efficiency of a micro-porous array. The simulation results show that the SEY of a roughened surface is affected significantly by the aspect ratio of the micro-pores and the surface porosity of the metal plate. Then, to verify the simulation results, we produce a micro-porous array on metal plates using photolithography and measure their SEYs. We show that the micro-porous array structure can efficiently suppress the SEY of metal materials, and the measurements agree quantitatively with the corresponding simulation results. Finally, we derive an analytical formula to evaluate easily the SEY suppression efficiency of the Ag micro-porous array. In total, the micro-porous array prop...
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