【作者】 吴伟；

【导师】 唐斌；

【作者基本信息】 电子科技大学 ， 信息与通信工程， 2007， 博士

【摘要】 宽带数字接收机已成为电子战侦察系统发展的必然趋势,其特征是利用靠近射频前端的高速ADC来实现宽开监视,利用数据率转换系统来降低后继数据率,实现无失真接收,后端利用DSP对所截获的低速率信号进行高精度信号特征提取。前端高速ADC与后端相对低速DSP之间的速率不匹配问题是宽带数字接收机面临的最大挑战。电子侦察中所面对的是参数完全未知的非合作信号,缺乏先验信息。由于匹配信号带宽的基带信号速率是在无失真条件下的最低数据率,因此,如何最大程度的降低数据率,缓解后继处理压力,实现对未知信号的无失真通带匹配接收已经成为目前数字侦察接收机的系统性关键技术和难点。本文围绕通带匹配数字侦察接收的理论基础、方案设计和系统架构,以及其中的关键技术和难点等问题展开深入研究,主要工作和贡献有:1、研究了电子战环境下通带匹配数字侦察接收的理论基础、体系架构和实现方案,提出了带通采样方案、数字下变频方案、数字信道化方案、引导式频谱融合方案、大时宽调频信号的频谱分时接收方案和频谱压缩方案等六种通带匹配接收的基本方案,分析优缺点,并指出了其中的关键技术和难点。研究了通带匹配接收中的快速频率估计技术和带宽参数估计技术,同时给出易于工程实现的相关快速算法。2、研究了基于带通采样的通带匹配数字接收方法。提出了可变速率直接ADC带通采样和可变速率直接带通抽取两种通带匹配接收结构,分别研究了系统性能恶化的解决方案,并分析了在硬件实现中所面临的困难,指出后者具有较强的工程可实现性。3、研究了基于数字下变频高效结构的通带匹配数字接收方法。提出了基于多级抽取比的可变带宽高效数字下变频方法,提出了基于有理数倍抽取比的高效带宽精匹配接收方法。这些方法以多相滤波结构为基础,有着较好的运算效率和工程可实现性。最后讨论了处理多个同时到达信号的通带匹配接收方案,并针对硬件实现中存在的问题提出了相应的解决方法。4、研究了基于可变带宽滤波器的通带匹配数字接收方法。提出了基于加权Minimax准则的可变带宽滤波器线性规划设计方法,提出了可变带宽FIR数字滤波器的高效WLS设计方法,提出了基于扩展傅里叶变换的可变带宽滤波器设计方法,以及基于EFT滤波器的通带匹配接收高效结构。应用这些可变带宽滤波器的优点在于只有一个直接决定带宽的可调谱参数,更新机制简单。最后讨论了基于可变带宽滤波器的多信号通带匹配接收方案。5、研究了基于频谱压缩的通带匹配数字接收方法。研究了频谱压缩与重构的基本原理,分析了Laguerre变换的频率卷绕特性,及其对LFM信号的频谱压缩特性,提出了基于Laguerre变换的宽带LFM信号频谱压缩数字接收方法。压缩信号可利用频谱恢复网络实现信号的重构,LFM信号的初始频率和调频斜率在频谱恢复后仍可较精确估计。6、研究了通带匹配数字侦察接收系统实验平台的设计和实现,其中包括实验平台的总体方案、高速A/D板、通带匹配接收处理板、PCI数据采集卡、高精度参数估计处理板和显控软件。测试结果显示实验平台具有较好的性能,能正确有效的实现信号通带匹配数字侦察接收。更多还原

【Abstract】 Wideband digital receiver has been a trend of the development of Electronic Warfare (EW) reconnaissance system. Its characteristics are using high-speed ADC closing to RF front-end to cover a wide survey band, and using data rate converter to decrease data rate and implement distortionless receiving, and then using DSP to implement precisely parameters estimation for low-speed data. However, there is a great challenge that the speed mismatch between front-end high-speed ADC and back-end low-speed DSP for the realization of wideband digital receiver. In electronic reconnaissance, prior information of the target signals isn’t provided in the complicated electromagnetic environment. The baseband signal rate of matching bandwidth is the lowest data rate in distortionless condition, so how to further decrease data rate and signal processing load, and implement distortionless bandwidth-matched receiving has been the key technique and difficulty for digital reconnaissance receiver. This dissertation focuses on the theoretic foundation, architecture and realization of bandwidth-matched digital reconnaissance receiving, and the interrelated key techniques and difficulties. The main contributions of this dissertation concentrate on a few aspects as follows:1. It is researched that the theoretic foundation, system design and realization of bandwidth-matched digital reconnaissance receiving in EW environment. It is proposed that six bandwidth-matched receiving schemes, such as bandpass sampling, digital downconversion (DDC), digital channelizer, leading spectral synthesis, spectrum time-sharing receiving for long pulse signals, and spectral compression. The advantage and disadvantage of them are analyzed while the key techniques and difficulties are discussed. Frequency and bandwidth estimation methods in bandwidth-matched receiving are also discussed, and some methods with good realizability are given.2. Bandwidth-matched digital receiving methods based on bandpass sampling are studied. Two bandwidth-matched digital receiving structures, variable-speed direct ADC bandpass sampling and variable-speed direct bandpass decimation, are proposed. However, these structures suffer from system performance worsening. To overcome these problems, some modified ways are presented. Meanwhile, the difficulties in hardware implementation are also analyzed, and some results show that the latter structure has better realizability.3. Bandwidth-matched digital receiving methods based on the efficient structure of DDC are studied. Based on multistage decimation ratio and rational decimation ratio, an efficient variable-bandwidth DDC and an efficient bandwidth-matched receiving method are proposed, respectively. Based on polyphase filtering structure, they achieve a significant reduction in complexity and computational cost. Finally, bandwidth-matched receiving methods are discussed for multiple simultaneous signals, and solutions for hardware implementation are given.4. Bandwidth-matched digital receiving methods based on variable-bandwidth filters (VBF) are studied. Firstly, a linear programming design technique is proposed for designing the variable-bandwidth linear-phase FIR filters in the weighted minimax sense. Then, it is presented that an efficient weighted-least-square (WLS) design method for FIR digital filters with variable bandwidth whereas the phase response is stable. Furthermore, a design technique of VBF based on the extended Fourier transform (EFT) and an efficient bandwidth-matched receiving structure based on EFT filters are proposed, respectively. The above VBFs are implemented with the aids of only one variable spectral parameter that determines the bandwidth and a simple updating routine. Finally, bandwidth-matched receiving methods based on VBF are discussed for multiple simultaneous signals.5. Bandwidth-matched digital receiving methods based on spectral compression are studied. Firstly, it is introduced that the foundation of spectral compression and reconstruction. Then, the frequency-warped characteristic of Laguerre transformation and its spectrum-compressed characteristic for LFM signal are analyzed. A novel spectrum-compressed digital receiving method using Laguerre transformation for LFM signal is proposed. The spectrum-compressed signal can be reconstructed by using the spectrum-reconstructed network. The modulation rate and initial frequency of the spectrum-reconstructed LFM signal can be estimated precisely.6. Design and Implementation of the bandwidth-matched digital receiving experimental systems, including the total scheme, high-speed A/D board, bandwidth-matched receiving processing board, PCI data acquisition card, parameters estimation processing board, and display and control software, are introduced. The test results show the experimental system has better performance and can validly implement signal bandwidth-matched digital receiving.更多还原