- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A Two-Step Nonlinear Chirp Scaling Method for Multichannel GEO Spaceborne-Airborne Bistatic SAR Spectrum Reconstructing and Focusing
摘要： Due to the high-altitude illumination and the separation of the receiver and transmitter, geosynchronous (GEO) spaceborne–airborne bistatic synthetic aperture radar (BiSAR) is more ?exible and accessible in remote sensing applications. In this paper, the Doppler characteristics of GEO BiSAR with a squint receiver are analyzed. It is found that the Doppler spectrum is generally aliased in GEO BiSAR regarding the low pulse repetition frequency (PRF) adopted by the GEO SAR. In order to suppress the ambiguity without adjusting the PRF of GEO SAR, the azimuth multichannel receiving technique is applied to the receiver and then the multichannel transfer function for GEO BiSAR is derived. However, the whole bandwidth of the imaging scene is much larger than that of the center point, which requires extra receiving channels to suppress the ambiguity and thereby increasing the system complexity. A two-step nonlinear chirp scaling (NLCS) method is proposed to obtain the well-focused image with reduced receiving channels. First, a preprocessing step is conducted to achieve space-variant range cell migration correction. After that, the ?rst-step NLCS processing is applied to equalize the 2-D space-variant Doppler centroid and thereby the Doppler bandwidth is decreased, i.e., the required number of receiving channels for reconstruction is reduced. Then, the unambiguous spectrum is reconstructed based on the proposed multichannel transfer function. Finally, the second-step NLCS processing is carried out to equalize the 2-D space-variant high-order Doppler parameters and obtain the well-focused image. The simulation results validate the effectiveness of the proposed method. With the proposed two-step NLCS method, the well-focused image for GEO BiSAR is obtained and the required number of receiving channels can be decreased, which is bene?cial to reducing the system complexity and hardware cost.
关键词： azimuth spectrum aliasing,geosynchronous synthetic aperture radar (GEO SAR),bistatic SAR (BiSAR),multichannel SAR,nonlinear chirp scaling (NLCS) algorithm,Ambiguity suppression
更新于2025-09-19 17:15:36
-
The Design of Nonlinear Chirp Based on the DSP Builder Technique
摘要： This paper, by analyzing the function Chirp, studies the software design and realization of the function. It offers a design plan based on the nonlinear Chirp signal of DSP Builder technique and designs the signal generator of the nonlinear Chirp based on the design flow of Matlab/Simulink/DSP Builder/QuartusⅡ. It also conducts simulation verification using the development software Matlab/Simulink and QuartusII, proving that the design can well realize the signal source Chirp. The experiment proves that the DSP Builder technique can modify the starting frequency, bandwidth and the frequency resolution of linear frequency modulation signals by changing the programming parameters. The method is proved to be simple in designing, convenient in modification, low in cost and it doesn’t involve any programming; therefore, it is easy to realize.
关键词： FPGA,Matlab/Simulink,Nonlinear Chirp,DSP Builder,QuartusⅡ
更新于2025-09-10 09:29:36