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摘要: 该文提出了基于脉冲组合编码的雷达探测模式,建立了脉冲编码雷达的基本概念和理论模型。利用多脉冲组合及其时间、频率、相位参量的调制,实现脉冲信号在时间域、频率域、或者时频域结合的编码,为解决传统的脉冲及连续波雷达系统参数相互耦合约束、及其对雷达性能的限制问题,提供了基于多脉冲组合探测的新方法及理论基础。该文着重介绍了多脉冲组合探测的编码、目标信号恢复方法,以及结合研制的合成孔径雷达开展的编码方法、性能评估等实验研究。研究及实验表明,通过采用分频带脉冲编码方法,可使雷达信号采样率突破奈奎斯特采样定理限制,降低系统的实现难度,实验系统中实现了4.8 GHz采样率对5 GHz带宽信号的采样及无失真恢复,成像分辨率达到0.03×0.03 m;通过采用增加占空比的时域脉冲编码方法,实现了信噪比改善超过20 dB的大幅度提高;通过针对合成孔径雷达的成像特性进行2维编码,去除了信号模糊问题,实现了成像幅宽超过90 km等先进性能指标。理论及实验结果验证了脉冲编码方法在提高雷达核心性能方面的显著优势,为高性能雷达系统的实现建立了新的技术途径。Abstract: This paper presents a radar working mode based on multi-pulse combination and coding, and the basic concept and theoretical model of pulse-coded radar are established. Using multi-pulse combination and the modulation of the time, frequency, and phase parameters, the pulse signal is coded in time domain, frequency domain, or time-frequency domain. Based on multi-pulse combination and coding, a new working method and theoretical basis are provided to solve the problem of coupling constraints among parameters of traditional pulse and continuous wave radars, which limits the performance of the radar system. Based on the fabricated Synthetic Aperture Radar (SAR) and its tests, the pulse coding, target signal recovery method, and pulse coding performance were studied. The study and test results show that the sampling rate of radar signals could be reduced to break through the limitation of Nyquist sampling theorem and simplify the difficulty of system implementation using frequency division pulse coding method. A 5 GHz bandwidth signal was sampled with 4.8 GHz and was recovered without distortion in the radar system, and an SAR imaging resolution of 0.03×0.03 m was realized. By using the time domain pulse coding method with an increase of duty cycle, the signal-to-noise ratio was improved by over 20 dB. By using the two-dimensional pulse coding method, the SAR signal ambiguity was removed, and the imaging swath of over 90 km was realized. The theoretical and test results verify the significant advantages of the pulse coding method in improving radar performance, by which a new technical approach for the realization of high performance radar system is provided.
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表 1 多脉冲编码信噪比改善结果(与单脉冲比较)
Table 1. Improvement of signal-to-noise ratio of multi-pulse coding (Comparison with single pulse)
回波接收窗口 1 2 3 4 5 6 7 8 9 10 11 SNR改善(dB) 13.59 9.61 11.37 11.37 11.37 11.37 11.37 11.37 11.37 9.61 13.59 表 2 多相编码
Table 2. Polyphase coding
编码方式 实现形式 2相编码 $0,{{π}} ,{{π}} ,0,0,{{π}} ,{{π}} ,0,0, ·\!·\!· $ 3相编码 $0,{{2{{π}} } / 3},0, ·\!·\!· $ 4相编码 $0,{{{π}} / 2}, - {{{π}} / 2},{{π}} ,{{π}} , - {{{π}} / 2},{{{π}} / 2},0, ·\!·\!· $ 5相编码 $0,{{2{{π}} } / 5}, - {{4{{π}} } / 5},{{2{{π}} } / 5},0,0,{{2{{π}} } / 5}, - {{4{{π}} } / 5},{{2{{π}} } / 5},0, ·\!·\!· $ 多相编码 ${\varphi _q} = {\varphi _{q - 1}} + q\frac{{2{{π}} }}{Q}$ -
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