Ultrahigh resolution synthetic aperture radar(SAR)imaging for ship targets is significant in SAR imaging,but it suffers from high frequency vibration of the platform,which will induce defocus into SAR imaging results....Ultrahigh resolution synthetic aperture radar(SAR)imaging for ship targets is significant in SAR imaging,but it suffers from high frequency vibration of the platform,which will induce defocus into SAR imaging results.In this paper,a novel compensation method based on the sinusoidal frequency modulation Fourier-Bessel transform(SFMFBT)is proposed,it can estimate the vibration errors,and the phase shift ambiguity can be avoided via extracting the time frequency ridge consequently.By constructing the corresponding compensation function and combined with the inverse SAR(ISAR)technique,well-focused imaging results can be obtained.The simulation imaging results of ship targets demonstrate the validity of the proposed approach.展开更多
By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulati...By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulation （UDFSPWM） respectively, the performances of the two modulation strategies are analyzed in detail. The circuit parameters, used in this paper, are fixed. When the systems, modulated by BSPWM and UDFSPWM, have the same switching frequency, the stabil- ity boundaries of the two systems are the same. However, when the equivalent switching frequencies of the two systems are the same, the BSPWM modulated system is more stable than the UDFSPWM modulated system. In addition, a convenient method of establishing the discrete-time model of piecewise smooth system is presented. Finally, the analytical results are confirmed by circuit simulations and experimental measurements.展开更多
This article proposed a new methodology and the principle of sinusoid modulated pulse MIG welding, and systematically established the universal mathematical model of computation of the parameters of the sinusoid modul...This article proposed a new methodology and the principle of sinusoid modulated pulse MIG welding, and systematically established the universal mathematical model of computation of the parameters of the sinusoid modulation pulse, achieving that the welding energy input can be effectively controlled and precisely regulated, the transition of pulse change is smooth and the welding process is stable and reliable. With the characteristics of sinusoidal waveform, such as infinite derivative continuity, eternal periodicity and limited control parameters, this article established the theoretical foundation for choiceness, unification and optimization of the parameters during the new sinusoid modulated pulse MIG welding. Bead-on-plate overlay welding is carried out on the pure aluminum sheet test sample for the test. The result indicated that during the welding process, the real-time current waveform is stable and clear; both the corresponding voltage and the instant welding energy waveform are very stable; the repeatability of the U-I graph plotted is high; its family of lines is clear, neat, and its distribution is concentrated showing that the welding process is stable and the neat and high quality ripple weld seam may be produced.展开更多
Sine Non-linear Chirp Keying(SNCK) is a kind of high-efficient modulation scheme, which provides a potential new beamforming method in communication and radar systems. It has been proved to have advantages in some par...Sine Non-linear Chirp Keying(SNCK) is a kind of high-efficient modulation scheme, which provides a potential new beamforming method in communication and radar systems. It has been proved to have advantages in some parameter estimation issues over conventional modulation schemes. In this paper, a novel transform termed as Discrete Sinusoidal Frequency Modulation transform(DSFMT) is proposed. Then, the DSFMT of SNCK signal is deduced and classified into three types, based on which, the time-bandwidth product is estimated by the proposed algorithm. Simulation results show that the noise has a signifi cant impact on the localization of the peak value and the time-bandwidth product can be estimated by using local ratio values when.展开更多
In this paper, we propose a method for characterizing a musical signal by extracting a set of harmonic descriptors reflecting the maximum information contained in this signal. We focus our study on a signal of orienta...In this paper, we propose a method for characterizing a musical signal by extracting a set of harmonic descriptors reflecting the maximum information contained in this signal. We focus our study on a signal of oriental music characterized by its richness in tone that can be extended to 1/4 tone, taking into account the frequency and time characteristics of this type of music. To do so, the original signal is slotted and analyzed on a window of short duration. This signal is viewed as the result of a combined modulation of amplitude and frequency. For this result, we apply short-term the non-stationary sinusoidal modeling technique. In each segment, the signal is represented by a set of sinusoids characterized by their intrinsic parameters: amplitudes, frequencies and phases. The modeling approach adopted is closely related to the slot window;therefore great importance is devoted to the study and the choice of the kind of the window and its width. It must be of variable length in order to get better results in the practical implementation of our method. For this purpose, evaluation tests were carried out by synthesizing the signal from the estimated parameters. Interesting results have been identified concerning the comparison of the synthesized signal with the original signal.展开更多
In this Letter,vortex phase and sinusoidal phase modulations of Hermite-Gaussian beams are studied theoretically and experimentally.The coding method of the experiment is introduced in detail,and the evolution law of ...In this Letter,vortex phase and sinusoidal phase modulations of Hermite-Gaussian beams are studied theoretically and experimentally.The coding method of the experiment is introduced in detail,and the evolution law of focus under different beam order(m,n)and topological charge(l)is given.In order to verify the accuracy of the generation experiment,the optical field distribution under sinusoidal vortex modulation is analyzed deeply.The relevant analysis and methods provided in this Letter have certain practical significance for the development of laser mode analysis,optical communication,and other fields.展开更多
基金supported by the National Natural Science Foundation of China(61871146)the Fundamental Research Funds for the Central Universities(FRFCU5710093720)。
文摘Ultrahigh resolution synthetic aperture radar(SAR)imaging for ship targets is significant in SAR imaging,but it suffers from high frequency vibration of the platform,which will induce defocus into SAR imaging results.In this paper,a novel compensation method based on the sinusoidal frequency modulation Fourier-Bessel transform(SFMFBT)is proposed,it can estimate the vibration errors,and the phase shift ambiguity can be avoided via extracting the time frequency ridge consequently.By constructing the corresponding compensation function and combined with the inverse SAR(ISAR)technique,well-focused imaging results can be obtained.The simulation imaging results of ship targets demonstrate the validity of the proposed approach.
基金supported by the National Natural Science Foundation of China (Grant No. 51277146)the Foundation of Delta Science,Technologythe Education Development Program for Power Electronics (Grant No. DREG2011003)
文摘By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulation （UDFSPWM） respectively, the performances of the two modulation strategies are analyzed in detail. The circuit parameters, used in this paper, are fixed. When the systems, modulated by BSPWM and UDFSPWM, have the same switching frequency, the stabil- ity boundaries of the two systems are the same. However, when the equivalent switching frequencies of the two systems are the same, the BSPWM modulated system is more stable than the UDFSPWM modulated system. In addition, a convenient method of establishing the discrete-time model of piecewise smooth system is presented. Finally, the analytical results are confirmed by circuit simulations and experimental measurements.
基金National Natural Science Foundation Project （50875088） Guangdong Province Science and Technology Research Project （2010B010700001）+1 种基金 Huangpu District Science and Technology Research Project （1021） Panyu District Science and Technology Research Project （2010-Z-22-1）.
文摘This article proposed a new methodology and the principle of sinusoid modulated pulse MIG welding, and systematically established the universal mathematical model of computation of the parameters of the sinusoid modulation pulse, achieving that the welding energy input can be effectively controlled and precisely regulated, the transition of pulse change is smooth and the welding process is stable and reliable. With the characteristics of sinusoidal waveform, such as infinite derivative continuity, eternal periodicity and limited control parameters, this article established the theoretical foundation for choiceness, unification and optimization of the parameters during the new sinusoid modulated pulse MIG welding. Bead-on-plate overlay welding is carried out on the pure aluminum sheet test sample for the test. The result indicated that during the welding process, the real-time current waveform is stable and clear; both the corresponding voltage and the instant welding energy waveform are very stable; the repeatability of the U-I graph plotted is high; its family of lines is clear, neat, and its distribution is concentrated showing that the welding process is stable and the neat and high quality ripple weld seam may be produced.
基金supported by Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory(KX152600015/ITD-U15006)National Natural Science Foundation of China(No.61401196)
文摘Sine Non-linear Chirp Keying(SNCK) is a kind of high-efficient modulation scheme, which provides a potential new beamforming method in communication and radar systems. It has been proved to have advantages in some parameter estimation issues over conventional modulation schemes. In this paper, a novel transform termed as Discrete Sinusoidal Frequency Modulation transform(DSFMT) is proposed. Then, the DSFMT of SNCK signal is deduced and classified into three types, based on which, the time-bandwidth product is estimated by the proposed algorithm. Simulation results show that the noise has a signifi cant impact on the localization of the peak value and the time-bandwidth product can be estimated by using local ratio values when.
文摘In this paper, we propose a method for characterizing a musical signal by extracting a set of harmonic descriptors reflecting the maximum information contained in this signal. We focus our study on a signal of oriental music characterized by its richness in tone that can be extended to 1/4 tone, taking into account the frequency and time characteristics of this type of music. To do so, the original signal is slotted and analyzed on a window of short duration. This signal is viewed as the result of a combined modulation of amplitude and frequency. For this result, we apply short-term the non-stationary sinusoidal modeling technique. In each segment, the signal is represented by a set of sinusoids characterized by their intrinsic parameters: amplitudes, frequencies and phases. The modeling approach adopted is closely related to the slot window;therefore great importance is devoted to the study and the choice of the kind of the window and its width. It must be of variable length in order to get better results in the practical implementation of our method. For this purpose, evaluation tests were carried out by synthesizing the signal from the estimated parameters. Interesting results have been identified concerning the comparison of the synthesized signal with the original signal.
文摘In this Letter,vortex phase and sinusoidal phase modulations of Hermite-Gaussian beams are studied theoretically and experimentally.The coding method of the experiment is introduced in detail,and the evolution law of focus under different beam order(m,n)and topological charge(l)is given.In order to verify the accuracy of the generation experiment,the optical field distribution under sinusoidal vortex modulation is analyzed deeply.The relevant analysis and methods provided in this Letter have certain practical significance for the development of laser mode analysis,optical communication,and other fields.
