【摘要】：作為一種高分辨成像雷達(dá)技術(shù),合成孔徑雷達(dá)(Synthetic Aperture Radar,SAR)在軍事偵察、遙感觀測(cè)等領(lǐng)域發(fā)揮了重要的作用。然而,單個(gè)發(fā)射和接收天線的常規(guī)SAR系統(tǒng)不能滿足對(duì)空間分辨率和測(cè)繪帶寬度日益增長(zhǎng)的需求。多天線技術(shù)(Multiple-Input Multiple-Output,MIMO)與SAR技術(shù)相結(jié)合,利用波形分集和天線分集,可以獲得遠(yuǎn)多于單個(gè)天線的空間自由度,從而實(shí)現(xiàn)高分辨率寬測(cè)繪帶成像,漸漸成為了人們的研究熱點(diǎn)。鑒于此,本文以SAR成像處理方法為基礎(chǔ),研究MIMO-SAR雷達(dá)的正交發(fā)射波形以及MIMO-SAR成像的基本處理方法。本文具體研究?jī)?nèi)容如下:(1)MIMO-SAR雷達(dá)正交發(fā)射波形設(shè)計(jì)。依據(jù)雷達(dá)發(fā)射信號(hào)正交性原理,本文研究了采用OFDM(Orthogonal Frequency Division Multiplexing)調(diào)制技術(shù)的正交波形集。首先,研究了子載波采用線性調(diào)頻(Linear Frequency Modulation,LFM)信號(hào)的正交信號(hào),對(duì)其自相關(guān)、互相關(guān)和模糊函數(shù)特性進(jìn)行了仿真分析。其次,研究了相位編碼(Phase Coded,PC)OFDM信號(hào)的正交性。采用混沌映射序列來產(chǎn)生新型的相位編碼信號(hào),該類信號(hào)具有保密性強(qiáng)、低截獲的優(yōu)點(diǎn)。針對(duì)混沌PC-OFDM信號(hào)的自相關(guān)性、互相關(guān)性、模糊函數(shù)以及多普勒容忍性展開仿真分析,并且討論了該類信號(hào)的優(yōu)缺點(diǎn)。(2)傳統(tǒng)單天線SAR成像方法研究。首先,分析SAR成像原理以及建立SAR信號(hào)回波模型。其次,采用距離-多普勒(Range-Doppler,R-D)算法進(jìn)行成像仿真研究,并利用RADARSAT-1雷達(dá)數(shù)據(jù)驗(yàn)證R-D算法的有效性。最后,針對(duì)稀疏場(chǎng)景的SAR成像,采用壓縮感知理論對(duì)SAR點(diǎn)目標(biāo)回波信號(hào)聚焦成像,實(shí)驗(yàn)表明壓縮感知在SAR成像旁瓣抑制方面有很大優(yōu)勢(shì)。(3)多天線SAR成像處理方法的研究。首先,分析常規(guī)SAR最小天線面積限制,建立三發(fā)三收基于OFDM-LFM正交信號(hào)的MIMO-SAR成像模型。其次,結(jié)合距離向高分辨的要求,對(duì)回波信號(hào)采用子帶拼接的方法在距離向合成大帶寬信號(hào)。最后,針對(duì)SAR方位向高分辨與寬測(cè)繪帶的要求,采用低脈沖重復(fù)頻率發(fā)射雷達(dá)信號(hào),在方位向利用多通道重建法,消除頻譜混疊。實(shí)驗(yàn)仿真驗(yàn)證該方法的有效性,與常規(guī)SAR成像算法的聚焦圖像進(jìn)行對(duì)比,表明MIMOSAR能夠?qū)崿F(xiàn)高分辨寬測(cè)繪帶成像。
[Abstract]:As a high resolution imaging radar technology, synthetic Aperture Radar (Synthetic Aperture Radar,SAR) plays an important role in military reconnaissance, remote sensing observation and other fields. However, conventional SAR systems with single transmitting and receiving antennas cannot meet the increasing demand for spatial resolution and the width of mapping bands. Combining multi-antenna technology (Multiple-Input Multiple-Output,MIMO) with SAR technology, using waveform diversity and antenna diversity, the spatial degree of freedom can be obtained much more than a single antenna, thus the high resolution and wide mapping band imaging has gradually become a hot research topic. In view of this, based on the SAR imaging processing method, the orthogonal transmitting waveform of MIMO-SAR radar and the basic processing method of MIMO-SAR imaging are studied in this paper. The main contents of this paper are as follows: (1) MIMO-SAR radar orthogonal waveform design. Based on the principle of orthogonality of radar transmitted signals, the orthogonal waveform set using OFDM (Orthogonal Frequency Division Multiplexing) modulation technique is studied in this paper. Firstly, the orthogonal signals with linear frequency modulated (Linear Frequency Modulation,LFM) subcarriers are studied, and the characteristics of autocorrelation, cross-correlation and ambiguity function are simulated and analyzed. Secondly, the orthogonality of phase coded (Phase Coded,PC) OFDM signal is studied. Chaotic mapping sequences are used to generate new phase coded signals, which have the advantages of high security and low interception. The self-correlation, cross-correlation, ambiguity function and Doppler tolerance of chaotic PC-OFDM signals are simulated, and the advantages and disadvantages of these signals are discussed. (2) the traditional single-antenna SAR imaging method is studied. Firstly, the principle of SAR imaging and the echo model of SAR signal are analyzed. Secondly, the range Doppler (Range-Doppler,R-D) algorithm is used for imaging simulation, and RADARSAT-1 radar data are used to verify the validity of R-D algorithm. Finally, for sparse SAR imaging, compression sensing theory is used to focus SAR point target echo signal. Experiments show that compression sensing has a great advantage in sidelobe suppression of SAR imaging. (3) Multi-antenna SAR imaging processing method is studied. Firstly, the limit of minimum antenna area of conventional SAR is analyzed, and a MIMO-SAR imaging model based on OFDM-LFM orthogonal signal is established. Secondly, according to the requirement of high resolution in range direction, the echo signal is synthesized with large bandwidth signal in range direction by subband splicing. Finally, according to the requirement of SAR azimuth high resolution and wide mapping band, low pulse repetition frequency is used to transmit radar signal, and multi-channel reconstruction method is used in azimuth direction to eliminate spectrum aliasing. The experimental results show that the proposed method is effective and compared with the focus image of conventional SAR imaging algorithm. It shows that MIMOSAR can achieve high resolution and wide mapping band imaging.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN958

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