A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a s...A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a set of fractional frequencies to create multiple measuring rulers with different metric ranges to determine the values of the tens,ones,tenths,and hundredths digits of the distance.Among these rulers,the one with the lowest frequency determines the maximum metric range,while the one with the highest frequency decides the highest achievable accuracy of the position system.For all rulers,the metric accuracy is uniquely determined by the phase accuracy of the detected PIM signals.With the all-phase Fourier transform method,the phases of the PIM signals at all fractional frequencies maintain almost the same accuracy,approximately 1°(about 1/360 wavelength in the positioning accuracy)at the signal-to-noise ratio(SNR)of 10 d B.Numerical simulations verify the effectiveness of the proposed method,improving the positioning accuracy of the cable PIM up to a millimeter level with the highest fractional frequency operating at 200 MHz.展开更多
With a pair of antennas spaced apart, an airborne passive location system measures phase differences of emitting signals. Regarded as cyclic ambiguities, the moduli of the measurements traditionally are resolved by ad...With a pair of antennas spaced apart, an airborne passive location system measures phase differences of emitting signals. Regarded as cyclic ambiguities, the moduli of the measurements traditionally are resolved by adding more antenna elements. This paper models the cyclic ambiguity as a component of the system state, of which the observability is analyzed and compared to that of the bear- ings-only passive location system. It is shown that the necessary and sufficient observability condition for the bearings-only passive location system is only the necessary observability condition for the passive location system with phase difference measurements, and that when the system state is observable, the cyclic ambiguities can be estimated by accumulating the phase difference measurements, thereby making the observer able to locate the emitter with high-precision.展开更多
In order to improve the performance of the traditional hybrid time-of-arrival（TOA）/angle-of-arrival（AOA）location algorithm in non-line-of-sight（NLOS）environments,a new hybrid TOA/AOA location estimation algorith...In order to improve the performance of the traditional hybrid time-of-arrival（TOA）/angle-of-arrival（AOA）location algorithm in non-line-of-sight（NLOS）environments,a new hybrid TOA/AOA location estimation algorithm by utilizing scatterer information is proposed.The linearized region of the mobile station（MS）is obtained according to the base station（BS）coordinates and the TOA measurements.The candidate points（CPs）of the MS are generated from this region.Then,using the measured TOA and AOA measurements,the radius of each scatterer is computed.Compared with the prior scatterer information,true CPs are obtained among all the CPs.The adaptive fuzzy clustering（AFC）technology is adopted to estimate the position of the MS with true CPs.Finally,simulations are conducted to evaluate the performance of the algorithm.The results demonstrate that the proposed location algorithm can significantly mitigate the NLOS effect and efficiently estimate the MS position.展开更多
This paper investigates the problem of target position estimation with a single-observer passive coherent location（PCL） system. An approach that combines angle with time difference of arrival（ATDOA） is used to est...This paper investigates the problem of target position estimation with a single-observer passive coherent location（PCL） system. An approach that combines angle with time difference of arrival（ATDOA） is used to estimate the location of a target. Compared with the TDOA-only method which needs two steps, the proposed method estimates the target position more directly. The constrained total least squares（CTLS） technique is applied in this approach. It achieves the Cramer–Rao lower bound（CRLB） when the parameter measurements are subject to small Gaussian-distributed errors. Performance analysis and the CRLB of this approach are also studied. Theory verifies that the ATDOA method gets a lower CRLB than the TDOA-only method with the same TDOA measuring error. It can also be seen that the position of the target affects estimating precision.At the same time, the locations of transmitters affect the precision and its gradient direction.Compared with the TDOA, the ATDOA method can obtain more precise target position estimation.Furthermore, the proposed method accomplishes target position estimation with a single transmitter,while the TDOA-only method needs at least four transmitters to get the target position. Furthermore,the transmitters＇ position errors also affect precision of estimation regularly.展开更多
This paper formulates a new framework to estimate the target position by adopting cuckoo search(CS)positioning algorithm. Addressing the nonlinear optimization problem is a crucial spot in the location system of time ...This paper formulates a new framework to estimate the target position by adopting cuckoo search(CS)positioning algorithm. Addressing the nonlinear optimization problem is a crucial spot in the location system of time difference of arrival(TDOA). With the application of the Levy flight mechanism, the preferential selection mechanism and the elimination mechanism, the proposed approach prevents positioning results from falling into local optimum. These intelligent mechanisms are useful to ensure the population diversity and improve the convergence speed. Simulation results demonstrate that the cuckoo localization algorithm has higher locating precision and better performance than the conventional methods. Compared with particle swarm optimization(PSO) algorithm and Newton iteration algorithm, the proposed method can obtain the Cram′er-Rao lower bound(CRLB) and quickly achieve the global optimal solutions.展开更多
Technology of passive location has broad prospects inapplications. In this paper, the sin- gle observer passive locationmethod using phase rate of change is introduced based on existingmeth- ods. This new method can o...Technology of passive location has broad prospects inapplications. In this paper, the sin- gle observer passive locationmethod using phase rate of change is introduced based on existingmeth- ods. This new method can obtain the direction of he target withphase information of two orthogonal interferometers on the observerand the radial distance with the corresponding phase rate of change.Then the target can be located with high speed and precision. Somelocating expressions are given When the flying posture of theobserver is change. Simulations show that this method is effective.展开更多
The conventional mono-station passive location techniques of direction finding are low in speed and accuracy, due to the little information available. In this paper, a novel measurement-rate (derivative) of phase diff...The conventional mono-station passive location techniques of direction finding are low in speed and accuracy, due to the little information available. In this paper, a novel measurement-rate (derivative) of phase difference from a two-element antenna array (interferometer) is introduced, accuracy of a passive location system with this measurement and directions of arrival (DOA) is analyzed, and the Cramer-Rao bound of location error of this system for 3D location is examined by simulations.展开更多
Under the scenario of dense targets in clutter, a multi-layer optimal data correlation algorithm is proposed. This algorithm eliminates a large number of false location points from the assignment process by rough corr...Under the scenario of dense targets in clutter, a multi-layer optimal data correlation algorithm is proposed. This algorithm eliminates a large number of false location points from the assignment process by rough correlations before we calculate the correlation cost, so it avoids the operations for the target state estimate and the calculation of the correlation cost for the false correlation sets. In the meantime, with the elimination of these points in the rough correlation, the disturbance from the false correlations in the assignment process is decreased, so the data correlation accuracy is improved correspondingly. Complexity analyses of the new multi-layer optimal algorithm and the traditional optimal assignment algorithm are given. Simulation results show that the new algorithm is feasible and effective.展开更多
Musculoskeletal pain is common. Because pain is subjective, objectively describing it is crucial. However, pain assessment may cause distress in patients;therefore, physical therapists (PTs) should conduct these tests...Musculoskeletal pain is common. Because pain is subjective, objectively describing it is crucial. However, pain assessment may cause distress in patients;therefore, physical therapists (PTs) should conduct these tests quickly and accurately. Simple and clear instructions are recommended for pain assessment. However, few studies have provided evidence to support this hypothesis. Correspondingly, this study aimed to confirm the effectiveness of specific verbal instructions for pain location during five consecutive Passive Straight Leg Raise (PSLR) tests. The 28 asymptomatic participants (age 27.4 ± 9.6 years) who provided informed consent received five consecutive PSLR tests: three without and two with specific verbal instructions to ascertain pain intensity, quality, and location. The participants drew pain locations on a body chart and described the pain intensity and quality after each test. All participants were interviewed regarding the differences they noted in the presence and absence of specific verbal instructions. Each pain location was classified into one of ten areas for statistical analysis. The proportion of participants who changed the pain location was compared between the tests using McNemar’s test, and the kappa coefficient was confirmed for consistency of pain location. There was a significant difference in the proportion of participants who changed their pain location between the second and third tests and from the third to the fourth test (McNemar’s test: p = 0.003). Kappa coefficients had low consistency (κ = 0.28) just after receiving the specific verbal instructions in the fourth test compared to the third test. Consistency improved in the fifth test (κ = 0.57);93% of the participants answered that the pain location had become clearer. This study revealed the effects of specific verbal instructions in identifying pain locations. This detailed information may help PTs provide appropriate treatment and contribute to reducing pain in clinical settings.展开更多
To solve the problem of multiple moving sources passive location, a novel blind source separa- tion （BSS） algorithm based on the muhiset canonical correlation analysis （MCCA） is presented by exploiting the differe...To solve the problem of multiple moving sources passive location, a novel blind source separa- tion （BSS） algorithm based on the muhiset canonical correlation analysis （MCCA） is presented by exploiting the different temporal structure of uncorrelated source signals first, and then on the basis of this algorithm, a novel multiple moving sources passive location method is proposed using time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements. The key technique of this location method is TDOA and FDOA joint estimation, which is based on BSS. By blindly separating mixed signals from multiple moving sources, the multiple sources location problem can be translated to each source location in turn, and the effect of interference and noise can also he removed. The simulation results illustrate that the performance of the MCCA algorithm is very good with relatively light computation burden, and the location algorithm is relatively simple and effective.展开更多
Technology of passive location has broad prospects in applications. In this paper, the method using the phase rate of change for the single observer passive location is introduced based on existing methods. One can ob...Technology of passive location has broad prospects in applications. In this paper, the method using the phase rate of change for the single observer passive location is introduced based on existing methods. One can obtain the direction of the target with phase information of two orthogonal interferometers on the observer and the radial distance with the corresponding phase rate of change. Then the target can be located with high speed and precision. A locating approach is given when the flying posture of t...展开更多
The two-station positioning system based on time difference and azimuth measurement has measurement redundancy. Therefore, not only can a positioning solution which is completely independent of the baseline length bet...The two-station positioning system based on time difference and azimuth measurement has measurement redundancy. Therefore, not only can a positioning solution which is completely independent of the baseline length between two stations be derived, but also the baseline length can be solved as an unknown quantity. These findings not only enhance the performance of the two-station positioning system, but also provide a design basis for the construction of a self-organizing dynamic intelligent positioning system.展开更多
This paper proposes a fingerprint matching method integrating transfer learning and online learning to tackle the challenges of environmental adaptability and dynamic interference resistance in photovoltaic(PV)array D...This paper proposes a fingerprint matching method integrating transfer learning and online learning to tackle the challenges of environmental adaptability and dynamic interference resistance in photovoltaic(PV)array DC arc fault location methods based on electromagnetic radiation(EMR)signals.Initially,a comprehensive analysis of the time–frequency characteristics of series arc EMR signals is carried out to pinpoint effective data sources that reflect fault features.Subsequently,a multi-kernel domain-adversarial neural network(MKDANN)is introduced to extract domain-invariant features,and a feature extractor designed specifically for fingerprint matching is devised.To reduce inter-domain distribution differences,a multi-kernel maximum mean discrepancy(MK-MMD)is integrated into the adaptation layer.Moreover,to deal with dynamic environmental changes in real-world situations,the support-class passive aggressive(SPA)algorithm is utilized to adjust model parameters in real time.Finally,MKDANN and SPA technologies are smoothly combined to build a fully operational fault location model.Experimental results indicate that the proposed method attains an overall fault location accuracy of at least 95%,showing strong adaptability to environmental changes and robust interference resistance while maintaining excellent online learning capabilities during model migration.展开更多
Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signal...Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.展开更多
For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved pe...For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.展开更多
Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location ...Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.展开更多
In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive inter...In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive intermodulation(PIM)interference may become an important factor limiting the system’s SNR.Whether it is a base station,an indoor distributed antenna system,or a satellite system,there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks.Especially for systems of high power and wide bandwidth such as 5G wireless communication,PIM interference is even more serious.Due to the complexity and uncertainty of PIM,measurement is the most important means to study and evaluate the PIM performance of wireless communication systems.In this review,the current main PIM measurement methods recommended by International Electrotechnical Commission(IEC)and other standard organizations are introduced,and several key challenges in PIM measurement and their solutions(including the design of PIM tester,the location of the PIM sources,the design of compact PIM anechoic chambers,and the evaluation methods of PIM anechoic chambers)are highlighted.These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.展开更多
文摘A novel method is developed by utilizing the fractional frequency based multirange rulers to precisely position the passive inter-modulation(PIM)sources within radio frequency(RF)cables.The proposed method employs a set of fractional frequencies to create multiple measuring rulers with different metric ranges to determine the values of the tens,ones,tenths,and hundredths digits of the distance.Among these rulers,the one with the lowest frequency determines the maximum metric range,while the one with the highest frequency decides the highest achievable accuracy of the position system.For all rulers,the metric accuracy is uniquely determined by the phase accuracy of the detected PIM signals.With the all-phase Fourier transform method,the phases of the PIM signals at all fractional frequencies maintain almost the same accuracy,approximately 1°(about 1/360 wavelength in the positioning accuracy)at the signal-to-noise ratio(SNR)of 10 d B.Numerical simulations verify the effectiveness of the proposed method,improving the positioning accuracy of the cable PIM up to a millimeter level with the highest fractional frequency operating at 200 MHz.
文摘With a pair of antennas spaced apart, an airborne passive location system measures phase differences of emitting signals. Regarded as cyclic ambiguities, the moduli of the measurements traditionally are resolved by adding more antenna elements. This paper models the cyclic ambiguity as a component of the system state, of which the observability is analyzed and compared to that of the bear- ings-only passive location system. It is shown that the necessary and sufficient observability condition for the bearings-only passive location system is only the necessary observability condition for the passive location system with phase difference measurements, and that when the system state is observable, the cyclic ambiguities can be estimated by accumulating the phase difference measurements, thereby making the observer able to locate the emitter with high-precision.
基金The National High Technology Research and Development Program of China(863Program)(No.2008AA01Z227)the National Natural Science Foundation of China(No.60872075)
文摘In order to improve the performance of the traditional hybrid time-of-arrival（TOA）/angle-of-arrival（AOA）location algorithm in non-line-of-sight（NLOS）environments,a new hybrid TOA/AOA location estimation algorithm by utilizing scatterer information is proposed.The linearized region of the mobile station（MS）is obtained according to the base station（BS）coordinates and the TOA measurements.The candidate points（CPs）of the MS are generated from this region.Then,using the measured TOA and AOA measurements,the radius of each scatterer is computed.Compared with the prior scatterer information,true CPs are obtained among all the CPs.The adaptive fuzzy clustering（AFC）technology is adopted to estimate the position of the MS with true CPs.Finally,simulations are conducted to evaluate the performance of the algorithm.The results demonstrate that the proposed location algorithm can significantly mitigate the NLOS effect and efficiently estimate the MS position.
基金supported by the National High Technology Research and Development Program of China(863 Program)(No.2012AA7031015)
文摘This paper investigates the problem of target position estimation with a single-observer passive coherent location（PCL） system. An approach that combines angle with time difference of arrival（ATDOA） is used to estimate the location of a target. Compared with the TDOA-only method which needs two steps, the proposed method estimates the target position more directly. The constrained total least squares（CTLS） technique is applied in this approach. It achieves the Cramer–Rao lower bound（CRLB） when the parameter measurements are subject to small Gaussian-distributed errors. Performance analysis and the CRLB of this approach are also studied. Theory verifies that the ATDOA method gets a lower CRLB than the TDOA-only method with the same TDOA measuring error. It can also be seen that the position of the target affects estimating precision.At the same time, the locations of transmitters affect the precision and its gradient direction.Compared with the TDOA, the ATDOA method can obtain more precise target position estimation.Furthermore, the proposed method accomplishes target position estimation with a single transmitter,while the TDOA-only method needs at least four transmitters to get the target position. Furthermore,the transmitters＇ position errors also affect precision of estimation regularly.
基金the National Natural Science Foundation of China(No.61571146)the Fundamental Research Funds for the Central Universities of China(No.HEUCFP201769)
文摘This paper formulates a new framework to estimate the target position by adopting cuckoo search(CS)positioning algorithm. Addressing the nonlinear optimization problem is a crucial spot in the location system of time difference of arrival(TDOA). With the application of the Levy flight mechanism, the preferential selection mechanism and the elimination mechanism, the proposed approach prevents positioning results from falling into local optimum. These intelligent mechanisms are useful to ensure the population diversity and improve the convergence speed. Simulation results demonstrate that the cuckoo localization algorithm has higher locating precision and better performance than the conventional methods. Compared with particle swarm optimization(PSO) algorithm and Newton iteration algorithm, the proposed method can obtain the Cram′er-Rao lower bound(CRLB) and quickly achieve the global optimal solutions.
文摘Technology of passive location has broad prospects inapplications. In this paper, the sin- gle observer passive locationmethod using phase rate of change is introduced based on existingmeth- ods. This new method can obtain the direction of he target withphase information of two orthogonal interferometers on the observerand the radial distance with the corresponding phase rate of change.Then the target can be located with high speed and precision. Somelocating expressions are given When the flying posture of theobserver is change. Simulations show that this method is effective.
文摘The conventional mono-station passive location techniques of direction finding are low in speed and accuracy, due to the little information available. In this paper, a novel measurement-rate (derivative) of phase difference from a two-element antenna array (interferometer) is introduced, accuracy of a passive location system with this measurement and directions of arrival (DOA) is analyzed, and the Cramer-Rao bound of location error of this system for 3D location is examined by simulations.
基金This project was supported by the National Natural Science Foundation of China (60672139, 60672140)the Excellent Ph.D. Paper Author Foundation of China (200237)the Natural Science Foundation of Shandong (2005ZX01).
文摘Under the scenario of dense targets in clutter, a multi-layer optimal data correlation algorithm is proposed. This algorithm eliminates a large number of false location points from the assignment process by rough correlations before we calculate the correlation cost, so it avoids the operations for the target state estimate and the calculation of the correlation cost for the false correlation sets. In the meantime, with the elimination of these points in the rough correlation, the disturbance from the false correlations in the assignment process is decreased, so the data correlation accuracy is improved correspondingly. Complexity analyses of the new multi-layer optimal algorithm and the traditional optimal assignment algorithm are given. Simulation results show that the new algorithm is feasible and effective.
文摘Musculoskeletal pain is common. Because pain is subjective, objectively describing it is crucial. However, pain assessment may cause distress in patients;therefore, physical therapists (PTs) should conduct these tests quickly and accurately. Simple and clear instructions are recommended for pain assessment. However, few studies have provided evidence to support this hypothesis. Correspondingly, this study aimed to confirm the effectiveness of specific verbal instructions for pain location during five consecutive Passive Straight Leg Raise (PSLR) tests. The 28 asymptomatic participants (age 27.4 ± 9.6 years) who provided informed consent received five consecutive PSLR tests: three without and two with specific verbal instructions to ascertain pain intensity, quality, and location. The participants drew pain locations on a body chart and described the pain intensity and quality after each test. All participants were interviewed regarding the differences they noted in the presence and absence of specific verbal instructions. Each pain location was classified into one of ten areas for statistical analysis. The proportion of participants who changed the pain location was compared between the tests using McNemar’s test, and the kappa coefficient was confirmed for consistency of pain location. There was a significant difference in the proportion of participants who changed their pain location between the second and third tests and from the third to the fourth test (McNemar’s test: p = 0.003). Kappa coefficients had low consistency (κ = 0.28) just after receiving the specific verbal instructions in the fourth test compared to the third test. Consistency improved in the fifth test (κ = 0.57);93% of the participants answered that the pain location had become clearer. This study revealed the effects of specific verbal instructions in identifying pain locations. This detailed information may help PTs provide appropriate treatment and contribute to reducing pain in clinical settings.
基金Supported by the National High Technology Research and Development Program of China(No.2009AAJ116,2009AAJ208,2010AA7010422)the National Science Foundation for Post-Doctoral Scientists of China(No.20080431379,200902671)the Hubei Natural Science Foundation(No.2009CDB031)
文摘To solve the problem of multiple moving sources passive location, a novel blind source separa- tion （BSS） algorithm based on the muhiset canonical correlation analysis （MCCA） is presented by exploiting the different temporal structure of uncorrelated source signals first, and then on the basis of this algorithm, a novel multiple moving sources passive location method is proposed using time difference of arrival （TDOA） and frequency difference of arrival （FDOA） measurements. The key technique of this location method is TDOA and FDOA joint estimation, which is based on BSS. By blindly separating mixed signals from multiple moving sources, the multiple sources location problem can be translated to each source location in turn, and the effect of interference and noise can also he removed. The simulation results illustrate that the performance of the MCCA algorithm is very good with relatively light computation burden, and the location algorithm is relatively simple and effective.
文摘Technology of passive location has broad prospects in applications. In this paper, the method using the phase rate of change for the single observer passive location is introduced based on existing methods. One can obtain the direction of the target with phase information of two orthogonal interferometers on the observer and the radial distance with the corresponding phase rate of change. Then the target can be located with high speed and precision. A locating approach is given when the flying posture of t...
文摘The two-station positioning system based on time difference and azimuth measurement has measurement redundancy. Therefore, not only can a positioning solution which is completely independent of the baseline length between two stations be derived, but also the baseline length can be solved as an unknown quantity. These findings not only enhance the performance of the two-station positioning system, but also provide a design basis for the construction of a self-organizing dynamic intelligent positioning system.
基金financially supported in part by the Natural Science Foundation of Fujian,China,under Grant 2021J01633.
文摘This paper proposes a fingerprint matching method integrating transfer learning and online learning to tackle the challenges of environmental adaptability and dynamic interference resistance in photovoltaic(PV)array DC arc fault location methods based on electromagnetic radiation(EMR)signals.Initially,a comprehensive analysis of the time–frequency characteristics of series arc EMR signals is carried out to pinpoint effective data sources that reflect fault features.Subsequently,a multi-kernel domain-adversarial neural network(MKDANN)is introduced to extract domain-invariant features,and a feature extractor designed specifically for fingerprint matching is devised.To reduce inter-domain distribution differences,a multi-kernel maximum mean discrepancy(MK-MMD)is integrated into the adaptation layer.Moreover,to deal with dynamic environmental changes in real-world situations,the support-class passive aggressive(SPA)algorithm is utilized to adjust model parameters in real time.Finally,MKDANN and SPA technologies are smoothly combined to build a fully operational fault location model.Experimental results indicate that the proposed method attains an overall fault location accuracy of at least 95%,showing strong adaptability to environmental changes and robust interference resistance while maintaining excellent online learning capabilities during model migration.
文摘Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.
基金supported by the National Natural Science Foundation of China(6107210761271300)+4 种基金the Shaanxi Industry Surmount Foundation(2012K06-12)the Arm and Equipment Pre-research Foundationthe Fundamental Research Funds for the Central Universities of China(K0551302006K5051202045K50511020024)
文摘For the joint time difference of arrival（TDOA） and angle of arrival（AOA） location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.
基金supported by the National Natural Science Foundation of China(6140236561271300)the 13th Five-Year Weaponry PreResearch Project。
文摘Based on the time differences of arrival(TDOA) and frequency differences of arrival(FDOA) measurements of the given planar stationary radiation source, the joint TDOA/FDOA location algorithm which solves the location of the target directly is proposed. Compared with weighted least squares(WLS) methods,the proposed algorithm is also suitable for well-posed conditions,and gets rid of the dependence on the constraints of Earth's surface. First of all, the solution formulas are expressed by the radial range. Then substitute it into the equation of the radial range to figure out the radial range between the target and the reference station. Finally use the solution expression of the target location to estimate the location of the target accurately. The proposed algorithm solves the problem that WLS methods have a large positioning error when the number of observation stations is not over-determined. Simulation results show the effectiveness of the proposed algorithm, including effectively increasing the positioning accuracy and reducing the number of observatories.
文摘In modern wireless communication systems,the signal-to-noise ratio(SNR)is one of the most important performance indicators.When the other radio frequency(RF)performance of the components is well designed,passive intermodulation(PIM)interference may become an important factor limiting the system’s SNR.Whether it is a base station,an indoor distributed antenna system,or a satellite system,there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks.Especially for systems of high power and wide bandwidth such as 5G wireless communication,PIM interference is even more serious.Due to the complexity and uncertainty of PIM,measurement is the most important means to study and evaluate the PIM performance of wireless communication systems.In this review,the current main PIM measurement methods recommended by International Electrotechnical Commission(IEC)and other standard organizations are introduced,and several key challenges in PIM measurement and their solutions(including the design of PIM tester,the location of the PIM sources,the design of compact PIM anechoic chambers,and the evaluation methods of PIM anechoic chambers)are highlighted.These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.
