The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the ph...The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the phase offsets due to frequency shift are linear. Based on this premise, the compensation processes are： firstly, the phase offsets between the baseband neighbor-symbols after clock recovery is unbiasedly estimated among the reference symbols; then, the receiving signals symbols are adjusted by the phase estimation value; finally, the phase offsets after adjusting are compensated by the least mean squares （LMS） algorithm. In order to express the compensation processes and ability clearly, the quadrature phase shift keying （QPSK） modulation signals are regarded as examples for Matlab simulation. BER simulations are carried out using the Monte-Carlo method. The learning curves are obtained to study the algorithm＇s convergence ability. The constellation figures are also simulated to observe the compensation results directly.展开更多
In recent years,thin-film lithium niobate(TFLN)electro-optic(EO)modulators have developed rapidly and are the core solution for the next generation of microwave photonics(MWP)problems.We designed and fabricated a dual...In recent years,thin-film lithium niobate(TFLN)electro-optic(EO)modulators have developed rapidly and are the core solution for the next generation of microwave photonics(MWP)problems.We designed and fabricated a dual-parallel Mach-Zehnder modulator(DPMZM)based on TFLN,achieving a 3 dB electro-electro(EE)bandwidth of 29 GHz and a low drive voltage(Vπ=6 V).The device we manufactured is metal-encapsulated.It is noteworthy that we proposed a single-channel Doppler frequency shift(DFS)measurement system based on this device and conducted verification experiments.We coupled light from an external laser into the chip and passed it through each of the two sub-MZMs of the DPMZM.These lights were modulated by echo signals and reference signals.By measuring the frequency of the output signal,we can obtain a DFS value without directional ambiguity.The success of this experiment marks a key step in the practical application of TFLN modulators in MWP.展开更多
The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This...The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.展开更多
A method is presented for near-Earth spacecraft or aviation vehicle's attitude rate estimation by using relative Doppler frequency shift; of the Global Positioning System (GPS) carrier. It comprises two GPS receiv...A method is presented for near-Earth spacecraft or aviation vehicle's attitude rate estimation by using relative Doppler frequency shift; of the Global Positioning System (GPS) carrier. It comprises two GPS receiving antennas, a signal processing circuit and an algorithm. The whole system is relatively simple, the cost and weight, as well as power consumption, are very low.展开更多
The Directions of Arrivals （DOAs）, speeds and distances of targets are all required for array signal processing. Based on the periodic phase shift of coherent pulse sequence waveform, a new estimation of multi-targ...The Directions of Arrivals （DOAs）, speeds and distances of targets are all required for array signal processing. Based on the periodic phase shift of coherent pulse sequence waveform, a new estimation of multi-targets＇ 2-Dimentional （2-D） DOA angle, Doppler frequency shift and relative time-delay is proposed. Based on a virtual sensor array constructed by pulse cumulating, the estinaations of azimuth, elevation, Doppler frequency shift and time-delay can be obtained simultaneously, and the least number of pulses could be two. This method is computationally efficient even in heavier noised environment, and all estimations are automatically paired in calculation process with no used to any plane sensor array and deal with many spectrum searching. Further more, this algorithm can be targets at the same time only by few sensors. The targets number that can deal with simultaneously is several times to the sensor number, which is the upper limit for normal algorithms such as ESPRIT and MUSIC. These characteristics would be very useful, especially, for aerial systems. Simulations demonstrate the capabilities of this method efficiently.展开更多
Code delay and Doppler shifted frequency could not be captured by using the conventional GPS receiver in strong interference environments because the received GPS signals which traveled a long distance are very weak. ...Code delay and Doppler shifted frequency could not be captured by using the conventional GPS receiver in strong interference environments because the received GPS signals which traveled a long distance are very weak. An anti-jamming GPS receiver is proposed. The interferences in the received signals are can- celled by using subspace projecting technique, and the resulting interference-free signals are processed by a weight vector which maximizes the signal-to-noise ratio. Simulation is conducted, and the results show that the method is valid.展开更多
Train-to-train(T2T)communication can provide protection for existing train-to-ground private network communication,and its channel characteristics directly affect the application of upper-layer communication technolog...Train-to-train(T2T)communication can provide protection for existing train-to-ground private network communication,and its channel characteristics directly affect the application of upper-layer communication technologies.In this study,based on the spatial distribution structure of railway operation scenarios and Fresnel zone theory,we propose a frequency allocation scheme for direct communication between tracking trains in flatland and long straight tunnel scenario.Then we use the estimation method of radio wave attenuation caused by rainfall to analyze the large-scale path loss fading of multi-band wireless channels.Furthermore,we derive the calculation equation of max Doppler frequency shift suitable for T2T communication and describe the multipath wave in the tunnel by ray tracing method to analyze small-scale fading.Simulation analysis shows that the Doppler shift value of T2T communication low frequency band is significantly lower than the frequency shift value of the train-to-ground communication under the same speed conditions.展开更多
To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its math...To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.展开更多
This poper presents a new method of estimating and correcting Doppler frequency shift in anM-ary (D)PSK receiver. The performance is discussed. Analytical and simulation results are presentedand the error probability ...This poper presents a new method of estimating and correcting Doppler frequency shift in anM-ary (D)PSK receiver. The performance is discussed. Analytical and simulation results are presentedand the error probability performance of the (D)PSK receiver is evaluated in the presence of the Doppler correction. It is shown from analytical and simulation results for constant Doppler shift that the methodperforms excellently.展开更多
There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood...There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.展开更多
An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and c...An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and cross correlation sequence between weak signals and strong signal can be computed,further modifying the local generate C/A code to drive the cross correlation to zero. The advantage of this method is that it does not require estimation of the strong signal amplitude and it partially independent of the data bit value.Simulation result shows it can eliminate the interference of 75%,and this method is at the cost of sensitivity loss of 0.28dB.展开更多
The basic principle ,optical system and measured results of the laser Doppler shift method for measuring slider flying characteristics are presented in this paper.
To estimate the motion parameters of a moving target before its passing by the closest point of approach （CPA） point in a low frequency analyzing and recording （LOFAR） field, an error-free theoretical method based...To estimate the motion parameters of a moving target before its passing by the closest point of approach （CPA） point in a low frequency analyzing and recording （LOFAR） field, an error-free theoretical method based on the joint measurement of target radiated noise＇s amplitude and frequency was presented. First, the error-free theoretical equations for target characteristic frequency, absolute velocity, the CPA, and amplitude of the radiation noise were derived by three equal interval measured values of the target amplitude and frequency. Then, the method to improve the calculation accuracy was given. Finally, the simulation and experiments were conducted in the air and showed the correctness of this method. By using one single piece of LOFAR, this method can calculate four target parameters and the relative error of each estimated parameter is less than 10%.展开更多
The output of each individual channel in multi-carrier system can be processed to detect moving targets by the approach used in tradition narrowband pulse Doppler（PD） radar and then using non-coherent integration to...The output of each individual channel in multi-carrier system can be processed to detect moving targets by the approach used in tradition narrowband pulse Doppler（PD） radar and then using non-coherent integration to promote signal noise ratio（SNR）. However, due to the difference of Doppler on sub-carriers, there occurs Doppler dispersion during non-coherent integration, which causes attenuation and extension on target＇s amplitude. Especially, it can deteriorate performance of target detection under wideband multicarrier system or fast-moving target scene. In this paper, a modified Fourier transform kernel is proposed to solve Doppler dispersion for multi-carrier chirp signal. It can achieve accumulation at the same frequency point for the target＇s Doppler of each subcarrier. The simulation results indicate that this method can effectively eliminate the integral loss caused by Doppler dispersion.展开更多
基金supported by the National Natural Science Foundation of China(60532030)
文摘The novel compensating method directly demodulates the signals without the carrier recovery processes, in which the carrier with original modulation frequency is used as the local coherent carrier. In this way, the phase offsets due to frequency shift are linear. Based on this premise, the compensation processes are： firstly, the phase offsets between the baseband neighbor-symbols after clock recovery is unbiasedly estimated among the reference symbols; then, the receiving signals symbols are adjusted by the phase estimation value; finally, the phase offsets after adjusting are compensated by the least mean squares （LMS） algorithm. In order to express the compensation processes and ability clearly, the quadrature phase shift keying （QPSK） modulation signals are regarded as examples for Matlab simulation. BER simulations are carried out using the Monte-Carlo method. The learning curves are obtained to study the algorithm＇s convergence ability. The constellation figures are also simulated to observe the compensation results directly.
基金supported by the National Natural Science Foundation of China(No.61727815)and the National Key Research and Development Program of China(No.2022YFB2803200).
文摘In recent years,thin-film lithium niobate(TFLN)electro-optic(EO)modulators have developed rapidly and are the core solution for the next generation of microwave photonics(MWP)problems.We designed and fabricated a dual-parallel Mach-Zehnder modulator(DPMZM)based on TFLN,achieving a 3 dB electro-electro(EE)bandwidth of 29 GHz and a low drive voltage(Vπ=6 V).The device we manufactured is metal-encapsulated.It is noteworthy that we proposed a single-channel Doppler frequency shift(DFS)measurement system based on this device and conducted verification experiments.We coupled light from an external laser into the chip and passed it through each of the two sub-MZMs of the DPMZM.These lights were modulated by echo signals and reference signals.By measuring the frequency of the output signal,we can obtain a DFS value without directional ambiguity.The success of this experiment marks a key step in the practical application of TFLN modulators in MWP.
文摘The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.
基金Supported by the National Aeronautics and Space Administration(NASA),Goddard Space Flight Center,USA,under Contract AN13709
文摘A method is presented for near-Earth spacecraft or aviation vehicle's attitude rate estimation by using relative Doppler frequency shift; of the Global Positioning System (GPS) carrier. It comprises two GPS receiving antennas, a signal processing circuit and an algorithm. The whole system is relatively simple, the cost and weight, as well as power consumption, are very low.
基金Supported by the NWPU Graduate Innovation Lab Cen-ter of China (No.04029)
文摘The Directions of Arrivals （DOAs）, speeds and distances of targets are all required for array signal processing. Based on the periodic phase shift of coherent pulse sequence waveform, a new estimation of multi-targets＇ 2-Dimentional （2-D） DOA angle, Doppler frequency shift and relative time-delay is proposed. Based on a virtual sensor array constructed by pulse cumulating, the estinaations of azimuth, elevation, Doppler frequency shift and time-delay can be obtained simultaneously, and the least number of pulses could be two. This method is computationally efficient even in heavier noised environment, and all estimations are automatically paired in calculation process with no used to any plane sensor array and deal with many spectrum searching. Further more, this algorithm can be targets at the same time only by few sensors. The targets number that can deal with simultaneously is several times to the sensor number, which is the upper limit for normal algorithms such as ESPRIT and MUSIC. These characteristics would be very useful, especially, for aerial systems. Simulations demonstrate the capabilities of this method efficiently.
基金supported by the National Natural Science Foundation of China (60472052 10577007)+1 种基金the Program for New Century Excellent Talents in University (2004)the National Key Lab Foundation of National Anti-Interference Communication Technology Laboratory
文摘Code delay and Doppler shifted frequency could not be captured by using the conventional GPS receiver in strong interference environments because the received GPS signals which traveled a long distance are very weak. An anti-jamming GPS receiver is proposed. The interferences in the received signals are can- celled by using subspace projecting technique, and the resulting interference-free signals are processed by a weight vector which maximizes the signal-to-noise ratio. Simulation is conducted, and the results show that the method is valid.
基金National Natural Science Foundation of China(No.61763023)Lanzhou Jiaotong University-Tianjin University Innovation Fund(No.20180519)。
文摘Train-to-train(T2T)communication can provide protection for existing train-to-ground private network communication,and its channel characteristics directly affect the application of upper-layer communication technologies.In this study,based on the spatial distribution structure of railway operation scenarios and Fresnel zone theory,we propose a frequency allocation scheme for direct communication between tracking trains in flatland and long straight tunnel scenario.Then we use the estimation method of radio wave attenuation caused by rainfall to analyze the large-scale path loss fading of multi-band wireless channels.Furthermore,we derive the calculation equation of max Doppler frequency shift suitable for T2T communication and describe the multipath wave in the tunnel by ray tracing method to analyze small-scale fading.Simulation analysis shows that the Doppler shift value of T2T communication low frequency band is significantly lower than the frequency shift value of the train-to-ground communication under the same speed conditions.
基金supported by the National Natural Science Foundation of China (Grant No.60872114)
文摘To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.
文摘This poper presents a new method of estimating and correcting Doppler frequency shift in anM-ary (D)PSK receiver. The performance is discussed. Analytical and simulation results are presentedand the error probability performance of the (D)PSK receiver is evaluated in the presence of the Doppler correction. It is shown from analytical and simulation results for constant Doppler shift that the methodperforms excellently.
文摘There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.
文摘An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and cross correlation sequence between weak signals and strong signal can be computed,further modifying the local generate C/A code to drive the cross correlation to zero. The advantage of this method is that it does not require estimation of the strong signal amplitude and it partially independent of the data bit value.Simulation result shows it can eliminate the interference of 75%,and this method is at the cost of sensitivity loss of 0.28dB.
文摘The basic principle ,optical system and measured results of the laser Doppler shift method for measuring slider flying characteristics are presented in this paper.
基金Project supported by the National Natural Science Foundation of China （No. 51209173）
文摘To estimate the motion parameters of a moving target before its passing by the closest point of approach （CPA） point in a low frequency analyzing and recording （LOFAR） field, an error-free theoretical method based on the joint measurement of target radiated noise＇s amplitude and frequency was presented. First, the error-free theoretical equations for target characteristic frequency, absolute velocity, the CPA, and amplitude of the radiation noise were derived by three equal interval measured values of the target amplitude and frequency. Then, the method to improve the calculation accuracy was given. Finally, the simulation and experiments were conducted in the air and showed the correctness of this method. By using one single piece of LOFAR, this method can calculate four target parameters and the relative error of each estimated parameter is less than 10%.
基金supported by the National Natural Science Foundation of China (61371107, 61362006)the Foundation of Key Lab. of Guangxi Broadband Wireless Communication & Signal Processing (GXKL061501)+1 种基金the Guangxi Natural Science Foundation (2014GXNSFBA118288)the Science and Technology on Information Transmission and Dissemination in Communication Networks Lab
文摘The output of each individual channel in multi-carrier system can be processed to detect moving targets by the approach used in tradition narrowband pulse Doppler（PD） radar and then using non-coherent integration to promote signal noise ratio（SNR）. However, due to the difference of Doppler on sub-carriers, there occurs Doppler dispersion during non-coherent integration, which causes attenuation and extension on target＇s amplitude. Especially, it can deteriorate performance of target detection under wideband multicarrier system or fast-moving target scene. In this paper, a modified Fourier transform kernel is proposed to solve Doppler dispersion for multi-carrier chirp signal. It can achieve accumulation at the same frequency point for the target＇s Doppler of each subcarrier. The simulation results indicate that this method can effectively eliminate the integral loss caused by Doppler dispersion.
