發(fā)布時間：2018-11-10 19:03

【摘要】：現(xiàn)代雷達在軍事設(shè)備,民事領(lǐng)域以及科研項目中應(yīng)用越來越廣泛,因而受到世界各國的重視。信號是雷達系統(tǒng)的中心,由于實現(xiàn)的靈活性,輸出頻率的準確度高等優(yōu),直接數(shù)字波形合成技術(shù)目前已經(jīng)被廣泛應(yīng)用于實際雷達工程中。隨著數(shù)字技術(shù)的發(fā)展,數(shù)字中頻技術(shù)也被引入雷達發(fā)射和接收系統(tǒng)中,進一步提高了雷達系統(tǒng)的性能。為了提高雷達的檢測能力,信號處理一般先采取匹配接收,使得輸出信噪比達到最大。同時,信號產(chǎn)生方式的固有局限性以及發(fā)射接收(T/R)的模擬器件限制等非線性因素,會給雷達接收信號引入復(fù)雜的雜散以及干擾,對雷達性能產(chǎn)生影響。本文主要對雷達系統(tǒng)的信號源以及發(fā)射接收通道中可能出現(xiàn)的非線性進行詳細的分析。首先介紹直接數(shù)字波形合成技術(shù)的基本原理,對DDS非線性導(dǎo)致的輸出信號中不同雜散成分進行詳細分析,包括相位截斷,幅度量化,DAC非線性。之后分析雷達發(fā)射接收鏈路中由模擬器件非線性導(dǎo)致的交調(diào)特性,并推導(dǎo)了系統(tǒng)各非線性指標間定量關(guān)系。仿真主要基于systemvue對雷達系統(tǒng)進行建模實現(xiàn)。本文重點仿真DDS及發(fā)射接收系統(tǒng)的非線性對于雷達探測性能的影響。通過DDS生成線性調(diào)頻信號(LFM),根據(jù)數(shù)字處理非線性導(dǎo)致的單頻信號雜散對LFM信號的雜散進行定性的分析,仿真分析其對雷達探測的影響;得出由DDS非線性產(chǎn)生的線性調(diào)頻信號中雜散噪聲對于匹配接收的影響主要是降低輸出信噪比,影響雷達探測目標的靈敏度。對于系統(tǒng)非線性主要分析不同目標環(huán)境下,由非線性引起的交調(diào)干擾對雷達探測的影響。仿真表明,無論單目標還是多目標環(huán)境,發(fā)射機非線性對雷達探測都不會產(chǎn)生影響;而接收機的非線性在多目標環(huán)境下產(chǎn)生的交調(diào)干擾會產(chǎn)生假目標,對雷達探測產(chǎn)生干擾。
[Abstract]:Modern radar is more and more widely used in military equipment, civil affairs and scientific research projects. Signal is the center of radar system. Because of the flexibility of realization and the high accuracy of output frequency, direct digital waveform synthesis technology has been widely used in practical radar engineering. With the development of digital technology, digital intermediate frequency technology is introduced into radar transmitting and receiving system, which improves the performance of radar system. In order to improve the detection ability of radar, the signal processing usually adopts matching reception, which makes the output signal-to-noise ratio maximum. At the same time, the inherent limitation of signal generation and the limitation of analog devices such as transmitting and receiving (T / R) will introduce complex spurious and interference to radar reception signal, which will have an impact on radar performance. In this paper, the signal source of radar system and the possible nonlinearity in transmitting and receiving channel are analyzed in detail. Firstly, the principle of direct digital waveform synthesis is introduced, and the different spurious components in the output signal caused by DDS nonlinearity are analyzed in detail, including phase truncation, amplitude quantization and DAC nonlinearity. After that, the intermodulation characteristics caused by the nonlinearity of analog devices in the radar transmit and receive link are analyzed, and the quantitative relationship among the nonlinear indexes of the system is deduced. The simulation is mainly based on systemvue to model the radar system. In this paper, the influence of DDS and the nonlinearity of transmitting and receiving system on radar detection performance is simulated. The linear frequency modulation signal (LFM),) is generated by DDS. According to the single frequency signal spurious caused by digital processing, the spurious signal of LFM signal is analyzed qualitatively, and the influence on radar detection is analyzed by simulation. It is concluded that the influence of spurious noise on matching reception in linear frequency modulated signals generated by DDS is mainly to reduce the output signal-to-noise ratio (SNR) and affect the sensitivity of radar target detection. For the system nonlinearity, the influence of nonlinear intermodulation jamming on radar detection is mainly analyzed in different target environments. Simulation results show that the transmitter nonlinearity has no effect on radar detection whether in single target environment or multi-target environment, while the cross-modulation jamming generated by receiver nonlinearity in multi-target environment will cause false target and jamming radar detection.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN95

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