A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the C...A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the CR-TR-UWB system detects the band of PU,and then sends prolate spheroidal wave functions（PSWF） pulses with the same limited band as PU＇s to reduce interference with PU.The receiver uses a notch filter before autocorrelation to eliminate NBI from PU.The simulation results show that the bit error rate（BER） performance of the CR-TR-UWB system is close to that of TR-UWB systems without NBI when the system is interfered by single or double NBIs with a signal to interference ratio（SIR） of 0 dB,and if the signal to noise ratio（SNR） is 10 dB and the SIR varies from-20 to 10 dB,BER performance varies no more than an order of magnitude.The system has excellent resistance to NBI,strong robustness BER performance at different SNRs,and smaller interference with the same frequency band PU.展开更多
The schemes and effects of electronically jamming GPS’s C/A code receivers are studied by using CW as the narrow band jamming signal and BPSK signal modulated by Gold code which is incoherent to that adopted by GPS ...The schemes and effects of electronically jamming GPS’s C/A code receivers are studied by using CW as the narrow band jamming signal and BPSK signal modulated by Gold code which is incoherent to that adopted by GPS as the wide band one. By simulating with Monte Carlo method and programming in Matlab language, the various jamming results in terms of bit error rate under several jamming scenarios are obtained. Through analyzing the simulation results and quantitative dependences of jamming effects on the distance from jammer to GPS receiver and the jammer’s height over ground, it is concluded that jamming with wide band jammer is much more effective than that with narrow band one.展开更多
The echo-enabled harmonic generation （EEHG） scheme holds promising prospects for efficiently generat- ing intense coherent radiation at very high harmonics of the initial seed laser. In this paper, we study the feas...The echo-enabled harmonic generation （EEHG） scheme holds promising prospects for efficiently generat- ing intense coherent radiation at very high harmonics of the initial seed laser. In this paper, we study the feasibility of operating the Shanghai X-ray free-electron laser test facility with a single stage EEHG setup. With a combina- tion of existing numerical codes, start-to-end simulations considering various three-dimensional effects have been carried out to show the possible performance of the EEHG FEL. Simulation results demonstrate that a single stage EEHG can generate high power soft X-ray radiation pulses with narrow bandwidth directly from UV seed lasers. With the help of the harmonic lasing technique or upgraded linac, we also show the possibility of generating coherent soft X-ray radiation in the ＂water window＂ with a single stage EEHG.展开更多
基金The National Research and Development Program of China(863 Program)(No.2007AA12Z238)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No. 12KJD510008)
文摘A cognitive radio transmitted reference ultra-wideband（CR-TR-UWB） system is proposed to improve the performance of TR-UWB systems with narrowband interference（NBI） from primary users（PU）.The transmitter of the CR-TR-UWB system detects the band of PU,and then sends prolate spheroidal wave functions（PSWF） pulses with the same limited band as PU＇s to reduce interference with PU.The receiver uses a notch filter before autocorrelation to eliminate NBI from PU.The simulation results show that the bit error rate（BER） performance of the CR-TR-UWB system is close to that of TR-UWB systems without NBI when the system is interfered by single or double NBIs with a signal to interference ratio（SIR） of 0 dB,and if the signal to noise ratio（SNR） is 10 dB and the SIR varies from-20 to 10 dB,BER performance varies no more than an order of magnitude.The system has excellent resistance to NBI,strong robustness BER performance at different SNRs,and smaller interference with the same frequency band PU.
文摘The schemes and effects of electronically jamming GPS’s C/A code receivers are studied by using CW as the narrow band jamming signal and BPSK signal modulated by Gold code which is incoherent to that adopted by GPS as the wide band one. By simulating with Monte Carlo method and programming in Matlab language, the various jamming results in terms of bit error rate under several jamming scenarios are obtained. Through analyzing the simulation results and quantitative dependences of jamming effects on the distance from jammer to GPS receiver and the jammer’s height over ground, it is concluded that jamming with wide band jammer is much more effective than that with narrow band one.
基金This work was partially supported by the National Development and Reform Commission （[201312347）, the National Natural Science Foundation of China （11475250, 11175240, 11275253 and 11322550） and the National Basic Research Program of China （2015CB859700）.
文摘The echo-enabled harmonic generation （EEHG） scheme holds promising prospects for efficiently generat- ing intense coherent radiation at very high harmonics of the initial seed laser. In this paper, we study the feasibility of operating the Shanghai X-ray free-electron laser test facility with a single stage EEHG setup. With a combina- tion of existing numerical codes, start-to-end simulations considering various three-dimensional effects have been carried out to show the possible performance of the EEHG FEL. Simulation results demonstrate that a single stage EEHG can generate high power soft X-ray radiation pulses with narrow bandwidth directly from UV seed lasers. With the help of the harmonic lasing technique or upgraded linac, we also show the possibility of generating coherent soft X-ray radiation in the ＂water window＂ with a single stage EEHG.
