The nomaal moveout correction is important to long-offset observations, especially deep layers. For isotropic media, the conventional two-term approximation of the normal moveout function assumes a small offset-to-dep...The nomaal moveout correction is important to long-offset observations, especially deep layers. For isotropic media, the conventional two-term approximation of the normal moveout function assumes a small offset-to-depth ratio and thus fails at large offset-to-depth ratios. We approximate the long-offset moveout using the Pade approximation. This method is superior to typical methods and flattens the seismic gathers over a wide range of offsets in multilayered media. For a four-layer model, traditional methods show traveltime errors of about 5 ms for offset-to-depth ratio of 2 and greater than 10 ms for offset-to-depth ratio of 3; in contrast, the maximum traveltime error for the [3, 3]-order Pade approximation is no more than 5 ms at offset-to-depth ratio of 3. For the Cooper Basin model, the maximum oft＇set-to-depth ratio for the [3, 3]-order Pade approximation is typically double of those in typical methods. The [7, 7]-order Pade approximation performs better than the [3.3]-order Pade armroximation.展开更多
This study investigates how frequency offsets of multitone jamming affect the fast frequencyhopped binary frequency shift keying （FFH/BFSK） self-normalizing （SNZ） receiver under additive white Gaussian noise （AWG...This study investigates how frequency offsets of multitone jamming affect the fast frequencyhopped binary frequency shift keying （FFH/BFSK） self-normalizing （SNZ） receiver under additive white Gaussian noise （AWGN）. The average bit-error-rate （BER） expressions of the FFH/BFSK SNZ receiver and the average BER expressions of an FFH/BFSK spread-spectrum （SS） communication system with frequency offsets of multitone jamming for the sake of understanding the simulation results better. Simulation results show that BER performance of the FFH/BFSK SNZ receiver with diversity under the worst case multitone jamming （MTJ） and AWGN suffers from multitone jamming＇s frequency offsets when the jamming power is moderate, which is validated by several simulations with different frequency offsets configured in multitone jamming. Therefore, an FFH/BFSK SNZ receiver under multitone jamming can be combated with the help of frequency offsets of multitone jamming.展开更多
This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmi...This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmitters and the uplink receiver will destroy orthogonality among different subcarriers, hence resulting in inter-carrier interference and multiuser interference. A two-stage frequency offset estimation algorithm based on subspace processing is proposed. The main advantage of the proposed method is that it can obtain the CFOs of all users simultaneously using only one OFDMA block. Compared with the previously known methods, it not only has a relatively low implementation complexity but is also suitable for random subchannel assignment.展开更多
提出一种双自调谐二阶广义积分器锁频环(frequency-locked loop based on double self-tuning second ordergeneralized integrator,DSSOGI-FLL)同步方法,该方法将自调谐滤波器(self-tuning filter)与优化的SOGI两种结构相级联,构成一...提出一种双自调谐二阶广义积分器锁频环(frequency-locked loop based on double self-tuning second ordergeneralized integrator,DSSOGI-FLL)同步方法,该方法将自调谐滤波器(self-tuning filter)与优化的SOGI两种结构相级联,构成一种双自调谐二阶广义积分器(self-tuning second order generalized integrator,SSOGI),该结构具有较SOGI更佳的滤波能力;同时,通过引入求差节点和一阶高通滤波器,使其具备了消除直流分量的能力;最后,应用幅值归一化算法对锁频环(FLL)结构进行参数设计,达到易于数字化实现的效果。仿真与实验结果验证文中所提DSSOGI-FLL方法的可行性与有效性。展开更多
基金supported by the National Natural Science Foundation of China(Nos.41130418 and 41374061)the National Major Project of China(No.2011ZX05008-006)and the Youth Innovation Promotion Association CAS(No.2012054)
文摘The nomaal moveout correction is important to long-offset observations, especially deep layers. For isotropic media, the conventional two-term approximation of the normal moveout function assumes a small offset-to-depth ratio and thus fails at large offset-to-depth ratios. We approximate the long-offset moveout using the Pade approximation. This method is superior to typical methods and flattens the seismic gathers over a wide range of offsets in multilayered media. For a four-layer model, traditional methods show traveltime errors of about 5 ms for offset-to-depth ratio of 2 and greater than 10 ms for offset-to-depth ratio of 3; in contrast, the maximum traveltime error for the [3, 3]-order Pade approximation is no more than 5 ms at offset-to-depth ratio of 3. For the Cooper Basin model, the maximum oft＇set-to-depth ratio for the [3, 3]-order Pade approximation is typically double of those in typical methods. The [7, 7]-order Pade approximation performs better than the [3.3]-order Pade armroximation.
基金supported by the National Natural Science Foundation of China under Grant No. 60502010the National Basic Research Program of China under Grant No. A1420080150the Science Foundation of National Defense Key Laboratory under Grant No.9140C0204010703
文摘This study investigates how frequency offsets of multitone jamming affect the fast frequencyhopped binary frequency shift keying （FFH/BFSK） self-normalizing （SNZ） receiver under additive white Gaussian noise （AWGN）. The average bit-error-rate （BER） expressions of the FFH/BFSK SNZ receiver and the average BER expressions of an FFH/BFSK spread-spectrum （SS） communication system with frequency offsets of multitone jamming for the sake of understanding the simulation results better. Simulation results show that BER performance of the FFH/BFSK SNZ receiver with diversity under the worst case multitone jamming （MTJ） and AWGN suffers from multitone jamming＇s frequency offsets when the jamming power is moderate, which is validated by several simulations with different frequency offsets configured in multitone jamming. Therefore, an FFH/BFSK SNZ receiver under multitone jamming can be combated with the help of frequency offsets of multitone jamming.
基金the Specialized Research Fund for the Doctoral Program of Higher Education, China Ministry of Education (No.20030003039).
文摘This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmitters and the uplink receiver will destroy orthogonality among different subcarriers, hence resulting in inter-carrier interference and multiuser interference. A two-stage frequency offset estimation algorithm based on subspace processing is proposed. The main advantage of the proposed method is that it can obtain the CFOs of all users simultaneously using only one OFDMA block. Compared with the previously known methods, it not only has a relatively low implementation complexity but is also suitable for random subchannel assignment.
文摘提出一种双自调谐二阶广义积分器锁频环(frequency-locked loop based on double self-tuning second ordergeneralized integrator,DSSOGI-FLL)同步方法,该方法将自调谐滤波器(self-tuning filter)与优化的SOGI两种结构相级联,构成一种双自调谐二阶广义积分器(self-tuning second order generalized integrator,SSOGI),该结构具有较SOGI更佳的滤波能力;同时,通过引入求差节点和一阶高通滤波器,使其具备了消除直流分量的能力;最后,应用幅值归一化算法对锁频环(FLL)结构进行参数设计,达到易于数字化实现的效果。仿真与实验结果验证文中所提DSSOGI-FLL方法的可行性与有效性。
