Multi-range-false-target(MRFT) jamming is particularly challenging for tracking radar due to the dense clutter and the repeated multiple false targets. The conventional association-based multi-target tracking(MTT) met...Multi-range-false-target(MRFT) jamming is particularly challenging for tracking radar due to the dense clutter and the repeated multiple false targets. The conventional association-based multi-target tracking(MTT) methods suffer from high computational complexity and limited usage in the presence of MRFT jamming.In order to solve the above problems, an efficient and adaptable probability hypothesis density(PHD) filter is proposed. Based on the gating strategy, the obtained measurements are firstly classified into the generalized newborn target and the existing target measurements. The two categories of measurements are independently used in the decomposed form of the PHD filter. Meanwhile,an amplitude feature is used to suppress the dense clutter. In addition, an MRFT jamming suppression algorithm is introduced to the filter. Target amplitude information and phase quantization information are jointly used to deal with MRFT jamming and the clutter by modifying the particle weights of the generalized newborn targets. Simulations demonstrate the proposed algorithm can obtain superior correct discrimination rate of MRFT, and high-accuracy tracking performance with high computational efficiency in the presence of MRFT jamming in the dense clutter.展开更多
We have investigated the quasiparticle dynamics and collective excitations in the quasi-one-dimensional material ZrTe_(5) using ultrafast optical pump-probe spectroscopy.Our time-domain results reveal two coherent osc...We have investigated the quasiparticle dynamics and collective excitations in the quasi-one-dimensional material ZrTe_(5) using ultrafast optical pump-probe spectroscopy.Our time-domain results reveal two coherent oscillations having extremely low energies of hω_(1)~0.33 me V(0.08 THz)and hω_(2)-1.9 me V(0.45 THz),which are softened as the temperature approaches two different critical temperatures(~54 K and~135 K).We attribute these two collective excitations to the amplitude mode of photoinduced dynamic charge density waves in ZrTe_(5) with tremendously small nesting wave vectors.Furthermore,a peculiar quasiparticle decay process associated with the hω_(2) mode with a timescale of~1-2 ps is found below the transition temperature T*(~135 K).Our findings provide pivotal information for studying the fluctuating order parameters and their associated quasiparticle dynamics in various low-dimensional topological systems and other materials.展开更多
The nature of a wireless communication channel is very unpredictable. To design a good communication link, it is required to know the statistical model of the channel accurately. The average symbol error probability(A...The nature of a wireless communication channel is very unpredictable. To design a good communication link, it is required to know the statistical model of the channel accurately. The average symbol error probability(ASER) was analyzed for different modulation schemes. A unified analytical framework was presented to obtain closed-form solutions for calculating the ASER of M-ary differential phase-shift keying(M-DPSK), coherent M-ary phase-shift keying(M-PSK), and quadrature amplitude modulation(QAM) over single or multiple Nakagami-m fading channels. Moreover, the ASER was estimated and evaluated by using the maximal ratio-combining(MRC) diversity technique. Simulation results show that an error rate of the fading channel typically depends on Nakagami parameters(m), space diversity(N), and symbol rate(M). A comparison between M-PSK, M-DPSK, and M-QAM modulation schemes was shown, and the results prove that M-ary QAM(M-QAM) demonstrates better performance compared to M-DPSK and M-PSK under all fading and non-fading conditions.展开更多
Watermarking system based on quantization index modulation （QIM） is increasingly popular in high payload applications,but it is inherently fragile against amplitude scaling attacks.In order to resist desynchronizati...Watermarking system based on quantization index modulation （QIM） is increasingly popular in high payload applications,but it is inherently fragile against amplitude scaling attacks.In order to resist desynchronization attacks of QIM digital watermarking,a low density parity check （LDPC） code-aided QIM watermarking algorithm is proposed,and the performance of QIM watermarking system can be improved by incorporating LDPC code with message passing estimation/detection framework.Using the theory of iterative estimation and decoding,the watermark signal is decoded by the proposed algorithm through iterative estimation of amplitude scaling parameters and decoding of watermark.The performance of the proposed algorithm is closer to the dirty paper Shannon limit than that of repetition code aided algorithm when the algorithm is attacked by the additive white Gaussian noise.For constant amplitude scaling attacks,the proposed algorithm can obtain the accurate estimation of amplitude scaling parameters.The simulation result shows that the algorithm can obtain similar performance compared to the algorithm without desynchronization.展开更多
基金supported by the National Natural Science Foundation of China (11472214)。
文摘Multi-range-false-target(MRFT) jamming is particularly challenging for tracking radar due to the dense clutter and the repeated multiple false targets. The conventional association-based multi-target tracking(MTT) methods suffer from high computational complexity and limited usage in the presence of MRFT jamming.In order to solve the above problems, an efficient and adaptable probability hypothesis density(PHD) filter is proposed. Based on the gating strategy, the obtained measurements are firstly classified into the generalized newborn target and the existing target measurements. The two categories of measurements are independently used in the decomposed form of the PHD filter. Meanwhile,an amplitude feature is used to suppress the dense clutter. In addition, an MRFT jamming suppression algorithm is introduced to the filter. Target amplitude information and phase quantization information are jointly used to deal with MRFT jamming and the clutter by modifying the particle weights of the generalized newborn targets. Simulations demonstrate the proposed algorithm can obtain superior correct discrimination rate of MRFT, and high-accuracy tracking performance with high computational efficiency in the presence of MRFT jamming in the dense clutter.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974070,11734006,11925408,and 11921004)the Frontier Science Project of Dongguan(Grant No.2019622101004)+5 种基金the National Key R&D Program of China(Grant Nos.2016YFA0300600,and 2018YFA0305700)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000)the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)the Beijing Natural Science Foundation(Grant No.Z180008)the Beijing Municipal Science and Technology Commission(Grant No.Z191100007219013)the CAS Interdisciplinary Innovation Team。
文摘We have investigated the quasiparticle dynamics and collective excitations in the quasi-one-dimensional material ZrTe_(5) using ultrafast optical pump-probe spectroscopy.Our time-domain results reveal two coherent oscillations having extremely low energies of hω_(1)~0.33 me V(0.08 THz)and hω_(2)-1.9 me V(0.45 THz),which are softened as the temperature approaches two different critical temperatures(~54 K and~135 K).We attribute these two collective excitations to the amplitude mode of photoinduced dynamic charge density waves in ZrTe_(5) with tremendously small nesting wave vectors.Furthermore,a peculiar quasiparticle decay process associated with the hω_(2) mode with a timescale of~1-2 ps is found below the transition temperature T*(~135 K).Our findings provide pivotal information for studying the fluctuating order parameters and their associated quasiparticle dynamics in various low-dimensional topological systems and other materials.
基金Project supported by Research Fund Chosun University 2014,Korea
文摘The nature of a wireless communication channel is very unpredictable. To design a good communication link, it is required to know the statistical model of the channel accurately. The average symbol error probability(ASER) was analyzed for different modulation schemes. A unified analytical framework was presented to obtain closed-form solutions for calculating the ASER of M-ary differential phase-shift keying(M-DPSK), coherent M-ary phase-shift keying(M-PSK), and quadrature amplitude modulation(QAM) over single or multiple Nakagami-m fading channels. Moreover, the ASER was estimated and evaluated by using the maximal ratio-combining(MRC) diversity technique. Simulation results show that an error rate of the fading channel typically depends on Nakagami parameters(m), space diversity(N), and symbol rate(M). A comparison between M-PSK, M-DPSK, and M-QAM modulation schemes was shown, and the results prove that M-ary QAM(M-QAM) demonstrates better performance compared to M-DPSK and M-PSK under all fading and non-fading conditions.
基金National Natural Science Foundation of China(No.61272432)Qingdao Science and Technology Development Plan(No.12-1-4-6-(10)-jch)
文摘Watermarking system based on quantization index modulation （QIM） is increasingly popular in high payload applications,but it is inherently fragile against amplitude scaling attacks.In order to resist desynchronization attacks of QIM digital watermarking,a low density parity check （LDPC） code-aided QIM watermarking algorithm is proposed,and the performance of QIM watermarking system can be improved by incorporating LDPC code with message passing estimation/detection framework.Using the theory of iterative estimation and decoding,the watermark signal is decoded by the proposed algorithm through iterative estimation of amplitude scaling parameters and decoding of watermark.The performance of the proposed algorithm is closer to the dirty paper Shannon limit than that of repetition code aided algorithm when the algorithm is attacked by the additive white Gaussian noise.For constant amplitude scaling attacks,the proposed algorithm can obtain the accurate estimation of amplitude scaling parameters.The simulation result shows that the algorithm can obtain similar performance compared to the algorithm without desynchronization.
