摘要 :
Frequency-swept interferometry (FSI) is intrinsically suitable for static ranging. For dynamic targets, its ranging accuracy is deteriorated by the Doppler phenomenon, and its measurement rate is restricted by the frequency sweep ...
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Frequency-swept interferometry (FSI) is intrinsically suitable for static ranging. For dynamic targets, its ranging accuracy is deteriorated by the Doppler phenomenon, and its measurement rate is restricted by the frequency sweep rate (usually kHz level), which prevents the acquisition of accurate time-varying distance details. To solve the problems, a novel microwave-photonic dynamic FSI (MP-DFSI) for fast ranging is proposed in this paper, which uses a single-frequency laser and an electro-optic modulator (EOM) to constitute a dual-sweep laser to provide two ideal mirrored laser sweeps. The instantaneous phases of the MP-DFSI signals are modulated by both the target distance and velocity in measurement, we investigate and model the modulation relationship, present a new data fusion demodulation method for high-accuracy fast ranging, which can effectively eliminate the Doppler error and recover the continuously-varying distance at each sampling point during a whole frequency-sweep cycle. Numerical verifications demonstrate that the measurement rate of the proposed MP-DFSI can reach 10 MHz with 1 urn ranging accuracy, showing the MP-DFSI has the ability of high-accuracy fast-ranging for dynamic targets.
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摘要 :
The inverse synthetic aperture radar (ISAR) imaging of non-uniformly rotating target and maneuvering target is a complicated task and the conventional range-Doppler (RD) ISAR technique does not work properly in this case. A novel ...
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The inverse synthetic aperture radar (ISAR) imaging of non-uniformly rotating target and maneuvering target is a complicated task and the conventional range-Doppler (RD) ISAR technique does not work properly in this case. A novel ISAR technique, named range-instantaneous Doppler (RID), has been proposed to deal with this difficulty. In this paper, the fractional Fourier transform (FrFT) and the CLEAN technique are combined for RID imaging and the detailed algorithm is presented. We use computer simulation to demonstrate its performance and the simulation results show its effectiveness.
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摘要 :
The inverse synthetic aperture radar (ISAR) imaging of non-uniformly rotating target and maneuvering target is a complicated task and the conventional range-Doppler (RD) ISAR technique does not work properly in this case. A novel ...
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The inverse synthetic aperture radar (ISAR) imaging of non-uniformly rotating target and maneuvering target is a complicated task and the conventional range-Doppler (RD) ISAR technique does not work properly in this case. A novel ISAR technique, named range-instantaneous Doppler (RID), has been proposed to deal with this difficulty. In this paper, the fractional Fourier transform (FrFT) and the CLEAN technique are combined for RID imaging and the detailed algorithm is presented. We use computer simulation to demonstrate its performance and the simulation results show its effectiveness.
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摘要 :
The inverse synthetic aperture radar (ISAR) imaging of non-uniformly rotating target and maneuvering target is a complicated task and the conventional range-Doppler (RD) ISAR technique does not work properly in this case. A novel ...
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The inverse synthetic aperture radar (ISAR) imaging of non-uniformly rotating target and maneuvering target is a complicated task and the conventional range-Doppler (RD) ISAR technique does not work properly in this case. A novel ISAR technique, named range-instantaneous Doppler (RID), has been proposed to deal with this difficulty. In this paper, the fractional Fourier transform (FrFT) and the CLEAN technique are combined for RID imaging and the detailed algorithm is presented. We use computer simulation to demonstrate its performance and the simulation results show its effectiveness.
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摘要 :
An instantaneous rotation rate (IRR) estimation algorithm based on the chirp rate of the scattering centre in the same Doppler cell is proposed to complete the cross-range scaling of the RID ISAR images.
摘要 :
Inverse synthetic aperture radar has been widely used in the imaging of space targets. The low earth-orbit target tends to introduce a time-variant Doppler shift in radar echo and the range-Doppler algorithm may fail in generating...
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Inverse synthetic aperture radar has been widely used in the imaging of space targets. The low earth-orbit target tends to introduce a time-variant Doppler shift in radar echo and the range-Doppler algorithm may fail in generating a focused image. In this paper, novel range-instantaneous-Doppler and range-instantaneous-chirp-rate methods are proposed based on the smoothed integrated high-resolution time-frequency-rate rep-resentation (SIHR-TFRR). The radar echo from one range cell is characterized as a multicomponent polynomial phase signal. The coefficients of the polynomial phase are estimated by the SIHR-TFRR algorithm. The effectiveness of the proposed methods are validated using the real-data experiments. Comparisons with the other methods are also provided.
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To solve the problem of cross-range scaling of non-cooperative target ISAR imaging, a corresponding analysis method is proposed based on echo phase polynomial and intrinsic mode components, to inhibit the endpoint effect in the em...
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To solve the problem of cross-range scaling of non-cooperative target ISAR imaging, a corresponding analysis method is proposed based on echo phase polynomial and intrinsic mode components, to inhibit the endpoint effect in the empirical mode decomposition process Rotation parameters of the target are obtained through instantaneous frequency analysis and the aspect angle during the imaging period is calculated to get the cross-range resolution of the target. Based on the principle of ISAR imaging, the instantaneous Doppler expression of the echo is deduced and a kind of empirical mode decomposition endpoint estimation method is brought forward. Combined with the third order PPS estimation of change rate of the echo's instantaneous frequency, the simulation results confirm the feasibility of the algorithm.
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The ALFA project aims at timely detection, tracking, classification, and intent assessment of LSS targets. The system relies on a heterogeneous sensor suite, including radar. The objective of the radar component is sector surveill...
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The ALFA project aims at timely detection, tracking, classification, and intent assessment of LSS targets. The system relies on a heterogeneous sensor suite, including radar. The objective of the radar component is sector surveillance including target classification. Since the revisit time needs to be short, classification must be done with very short time-on-target. Based on measurements, three suitable features for classification of two relevant target classes, i.e., small aircraft and helicopters, have been developed. These features exploit the targets' micro-Doppler characteristics and their evolution over time. Best classification performance is obtained by using a combination of these features and by considering the variation of the features' distributions depending on the signal-to-noise ratio.
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Micro-Doppler (m-D) is a useful feature of radar target, as an important characteristic for radar target detection, recognition, and classification. However, since the form of m-D signals is always multi-component, the signals usu...
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Micro-Doppler (m-D) is a useful feature of radar target, as an important characteristic for radar target detection, recognition, and classification. However, since the form of m-D signals is always multi-component, the signals usually need to be separated before feature extraction. A method for separation the m-D signals is proposed based on direction pattern. In this paper, we first obtain the Time Frequency Distribution (TFD) of the target echo by Short-Time Fourier Transformer (STFT). Then the local maxima algorithm is applied for the instantaneous frequency (IF) track coherence. Finally, the direction patter algorithm is used to separate the m-D signals. Simulation results indicate that the proposed method is effective.
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The knowledge of wind velocities at different heights is critical for the study of atmospheric dynamics. Over the last three decades, wind profiler radars have been successfully deployed to obtain altitude profiles of wind velocit...
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The knowledge of wind velocities at different heights is critical for the study of atmospheric dynamics. Over the last three decades, wind profiler radars have been successfully deployed to obtain altitude profiles of wind velocities with a high temporal resolution. Wind Profilers are coherent pulsed Doppler radars operating in VHF or UHF bands. They estimate the wind velocity with the help of Doppler spectra obtained by analyzing the backscattered signal from the atmospheric radio refractive index fluctuations. As the backscattered signal is weak, accurate estimation of the wind velocity to higher heights require sophisticated signal processing methods and often contribution of human experts. Computation of moments by various statistical methods, fuzzy logic approach and neural network techniques have been reported by a few researchers, which have unique advantages and disadvantages with better performing techniques the mathematical complexity increases manifolds. This paper proposes a wind profile tracing algorithm which traces the wind profile by computationally simple method. The proposed method divides the Doppler spectra into sections of five range-bins each. Then it identifies prospective wind profile `candidate traces'. Certain properties of the Doppler spectrum viz., signal power, spectral width and wind shear, have been parameterized and a `cost function' with non-linear weights is designed. A trace with maximum cost function is selected and the profile is completed maintaining the continuity with the adjacent sections. This method is computationally much simpler compared to contemporary leading methods and shows very encouraging performance on the data of almost all atmospheric conditions. Due to low computational complexity, this method has a high potential for `real-time automated' Doppler profile tracing
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