Low-frequency signals have been proven valuable in the fields of target detection and geological exploration.Nevertheless,the practical implementation of these signals is hindered by large antenna diameters,limiting t...Low-frequency signals have been proven valuable in the fields of target detection and geological exploration.Nevertheless,the practical implementation of these signals is hindered by large antenna diameters,limiting their potential applications.Therefore,it is imperative to study the creation of lowfrequency signals using antennas with suitable dimensions.In contrast to conventional mechanical antenna techniques,our study generates low-frequency signals in the spatial domain utilizing the principle of the Doppler effect.We also defines the antenna array architecture,the timing sequency,and the radiating element signal waveform,and provides experimental prototypes including 8/64 antennas based on earlier research.In the conducted experiments,121 MHz,40 MHz,and 10 kHz composite signals are generated by 156 MHz radiating element signals.The composite signal spectrum matches the simulations,proving our low-frequency signal generating method works.This holds significant implications for research on generating low-frequency signals with small-sized antennas.展开更多
Recent experimental results of the Doppler effect formula verification are reported. The moving emitters are hydrogen atoms in the excited state. The results of the work corroborate the classical not the relativistic,...Recent experimental results of the Doppler effect formula verification are reported. The moving emitters are hydrogen atoms in the excited state. The results of the work corroborate the classical not the relativistic,formula for the Doppler effect.展开更多
The effect of range-Doppler coupling caused by aircraft moving at very high speed makes trouble on selection of waveform parameters by using frequency-modulated interrupted continuous wave (FMICW) or frequency-coded p...The effect of range-Doppler coupling caused by aircraft moving at very high speed makes trouble on selection of waveform parameters by using frequency-modulated interrupted continuous wave (FMICW) or frequency-coded pulse (FCP). It also limits the increasing of coherent integration time. In this paper, application of coherent phase-coded pulse train (CPCPT) solves range-Doppler coupling well. Relevant processing of CPCPT consists of three parts: Doppler preprocessing, pulse compression, and Doppler post-processing. The velocity information obtained by Doppler preprocessing is used for better pulse compression and range tracking. Doppler post-processing with range tracking could make longer coherent accumulation for better detection of target and higher velocity resolution. Finally, examples of data simulation are given to demonstrate the achievements mentioned above.展开更多
Spatial precession is a special micro-motion of the spinning-directional target, and the micro-Doppler signature of the cone-shaped target with precession is studied. The micro-motion model of precession is built firs...Spatial precession is a special micro-motion of the spinning-directional target, and the micro-Doppler signature of the cone-shaped target with precession is studied. The micro-motion model of precession is built first, and then the micro-Doppler model is developed based on the proposed concept of micro-motion ma- trix, by which the theoretical formula of micro-Doppler signature of precession is derived. In order to further approach to the actual case, the occlusion effect is firstly considered in micro-Doppler, and the simulated result with occlusion effect is well in accordance with the measured result in microwave anechoic chamber, which suggests that the micro-motion model and micro-Doppler model of precession are both valid.展开更多
Target micromotion not only plays an important role in target recognition but also leads to esoteric characteristics in synthetic aperture radar （SAR） imaging. This paper finds out an interesting phenomenon, i.e. th...Target micromotion not only plays an important role in target recognition but also leads to esoteric characteristics in synthetic aperture radar （SAR） imaging. This paper finds out an interesting phenomenon, i.e. the angular extent effect, in micro-motion target images formulated by the polar format algorithm. A micromotion target takes on multiple pairs of paired echoes （PEs） around the true point, and each PE extends for an angle which is exactly equal to the angular extent of the synthetic aperture, regardless of the micromotion frequency. The effect is derived and interpreted by using the characteristics of Bessel functions. Then it is demonstrated by simulation experiments of a target with different micromotion frequencies. The revelation and interpretation of the effect is highly beneficial to micromotion-target SAR image understanding as wel as target recognition.展开更多
基金Science and Technology Project of Aerospace Information Research Institute,Chinese Academy of Sciences(Y910340Z2F)Science and Technology Project of BBEF(E3E2010201)。
文摘Low-frequency signals have been proven valuable in the fields of target detection and geological exploration.Nevertheless,the practical implementation of these signals is hindered by large antenna diameters,limiting their potential applications.Therefore,it is imperative to study the creation of lowfrequency signals using antennas with suitable dimensions.In contrast to conventional mechanical antenna techniques,our study generates low-frequency signals in the spatial domain utilizing the principle of the Doppler effect.We also defines the antenna array architecture,the timing sequency,and the radiating element signal waveform,and provides experimental prototypes including 8/64 antennas based on earlier research.In the conducted experiments,121 MHz,40 MHz,and 10 kHz composite signals are generated by 156 MHz radiating element signals.The composite signal spectrum matches the simulations,proving our low-frequency signal generating method works.This holds significant implications for research on generating low-frequency signals with small-sized antennas.
文摘Recent experimental results of the Doppler effect formula verification are reported. The moving emitters are hydrogen atoms in the excited state. The results of the work corroborate the classical not the relativistic,formula for the Doppler effect.
文摘The effect of range-Doppler coupling caused by aircraft moving at very high speed makes trouble on selection of waveform parameters by using frequency-modulated interrupted continuous wave (FMICW) or frequency-coded pulse (FCP). It also limits the increasing of coherent integration time. In this paper, application of coherent phase-coded pulse train (CPCPT) solves range-Doppler coupling well. Relevant processing of CPCPT consists of three parts: Doppler preprocessing, pulse compression, and Doppler post-processing. The velocity information obtained by Doppler preprocessing is used for better pulse compression and range tracking. Doppler post-processing with range tracking could make longer coherent accumulation for better detection of target and higher velocity resolution. Finally, examples of data simulation are given to demonstrate the achievements mentioned above.
文摘Spatial precession is a special micro-motion of the spinning-directional target, and the micro-Doppler signature of the cone-shaped target with precession is studied. The micro-motion model of precession is built first, and then the micro-Doppler model is developed based on the proposed concept of micro-motion ma- trix, by which the theoretical formula of micro-Doppler signature of precession is derived. In order to further approach to the actual case, the occlusion effect is firstly considered in micro-Doppler, and the simulated result with occlusion effect is well in accordance with the measured result in microwave anechoic chamber, which suggests that the micro-motion model and micro-Doppler model of precession are both valid.
基金supported by the National Natural Science Foundationof China(6130214861101182)
文摘Target micromotion not only plays an important role in target recognition but also leads to esoteric characteristics in synthetic aperture radar （SAR） imaging. This paper finds out an interesting phenomenon, i.e. the angular extent effect, in micro-motion target images formulated by the polar format algorithm. A micromotion target takes on multiple pairs of paired echoes （PEs） around the true point, and each PE extends for an angle which is exactly equal to the angular extent of the synthetic aperture, regardless of the micromotion frequency. The effect is derived and interpreted by using the characteristics of Bessel functions. Then it is demonstrated by simulation experiments of a target with different micromotion frequencies. The revelation and interpretation of the effect is highly beneficial to micromotion-target SAR image understanding as wel as target recognition.
