Moving target imaging of a dual-channel ISAL with binary phase shift keying signals and large squint angles

Abstract

A dual-channel inverse synthetic aperture ladar imaging experimental system based on wide-pulse binary phase coded signals and its moving target imaging are introduced. The analysis, simulation, and experimental data processing results of binary phase coded signal Doppler compensation and pulse compression are included. The method of motion phase error estimation based on interferometric processing and the imaging method with small computation in the case of large squint angles are proposed, and the simulation results are presented. The effectiveness of the imaging method is verified by experimental data processing. Doppler frequency curves are estimated based on time-frequency analysis of echo signals, and the coarse compensation of motion phase error is realized. According to the interferometric phase and coherence coefficient of dual-channel echo signals’ time-frequency analysis, the coherence of the dual-channel echo signals is checked, and along-track interferometry can be applied to the precise compensation. The stable interferometric phase and increased coherence coefficient of actual dual-channel data imaging results indicate the effectiveness of the motion phase error compensation method proposed. Considering characteristics of inverse synthetic aperture ladar (ISAL) imaging, after dividing echo signals into multiple sub-apertures, range-Doppler algorithm and sub-aperture stitching are adopted, the stitched image is corrected geometrically through Stolt transformation, and the computation is reduced.

Laser Synthetic Aperture Coherent Imaging for Micro-Rotating Objects Based on Array Detectors

“…3) Resolution of the single-frame complex image Assume that size of the detector is a , the focal length and aperture of the telescope are f and D . The far-field condition requires that the object distance 0 R satisfy 2 0 2 RD   (8) In the far field condition, the resolutions corresponding to the detector size of the system and the diffraction limit of the telescope are…”

“…Based on narrow-pulse laser signal, Aerospace Information Research Institute, Chinese Academy of Sciences completed ISAL imaging of the 83 m-away cooperative object and the 165 maway non-cooperative object in 2021, and the resolution of the imaging results was better than that of the real aperture corresponding to the beamwidth [7]. In the case of a large squint angle, the institute realized ISAL imaging of the cooperative object by binary phase shift keying (BPSK) signal and compensated for the motion phase error in 2022 [8]. Based on the concept of traditional ISAL, which images in range direction and azimuth direction, the feasibility of the scheme that ISAL with Coherent Array Detectors (CAD) images in the pitch direction and azimuth direction is analyzed, and the Laser Synthetic Aperture Coherent (LSAC) imaging method based on the array detectors is introduced.…”

Imaging and detection method for low signal-to-noise ratio airborne synthetic aperture ladar signals

“…Limited by the laser’s average power, the high pulse repetition frequency (PRF) of the SAL will result in lower peak-power of the laser, thereby reducing the echo signal’s single-pulse SNR. In the case of a low SNR, the coherence between channels becomes worse, and the vibration phase-error compensation method based on interferometry is difficult to apply 7 – 10 Therefore, it is important to study the SAL signal processing methods of airborne SAL low SNR signals under vibration and beam-broadening conditions.…”

“…In the case of a low SNR, the coherence between channels becomes worse, and the vibration phase-error compensation method based on interferometry is difficult to apply. [7][8][9][10] Therefore, it is important to study the SAL signal processing methods of airborne SAL low SNR signals under vibration and beam-broadening conditions.…”