Waveform Design for Active Sensing Systems: A Computational Approach
Waveform Design for Active Sensing Systems: A Computational Approach
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发表时间：
2012-07
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通讯作者：
Jian Li;Hao He
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作者：
Jian Li;Hao He
主动传感应用，如雷达、声纳和医学成像，需要适当的探测波形设计。良好的合成波形可以显著提高系统的信干扰比、频谱遏制、波束模式匹配、目标参数估计等性能。这项工作的重点是利用计算算法设计探测波形。我们首先研究设计具有良好相关特性的波形，这些波形在距离压缩、信道估计和扩频等应用中广泛使用。我们考虑单序列的设计和一组序列的设计，前者只有自相关，后者有自相关和互相关。所提出的算法利用FFT（快速傅立叶变换）操作，可以有效地生成以前难以合成的长序列。我们提出了从所提出的算法框架中产生的序列相关性下界的一个新的推导。我们证明了新设计的序列可以接近这样的下界。时延相关函数的二维扩展是模糊函数（AF），它涉及多普勒频移。我们概述了自动对焦特性，并讨论了如何在离散形式中最小化自动对焦副瓣。除了良好的相关特性外，我们还考虑了在避免预留频带或强电子干扰的情况下所需的阻带约束。我们提出了一种同时考虑相关和阻带约束的算法。最后我们考虑了发射波束图合成，特别是在宽带情况下。我们利用傅里叶变换建立了期望的波束模式和底层波形之间的关系。我们强调了MIMO（多输入多输出）系统的波形多样性增加的设计自由度。
Active sensing applications such as radar, sonar and medical imaging, demand proper designs of the probing waveform. A well-synthesized waveform can significantly increase the system performance in terms of signal-to-interference ratio, spectrum containment, beampattern matching, target parameter estimation and so on. The focus of this work is on designing probing waveforms using computational algorithms. We first investigate designing waveforms with good correlation properties, which are widely useful in applications including range compression, channel estimation and spread spectrum. We consider both the design of a single sequence and that of a set of sequences, the former with only auto-correlations and the latter with auto- and cross-correlations. The proposed algorithms leverage FFT (fast Fourier transform) operations and can efficiently generate long sequences that were previously difficult to synthesize. We present a new derivation of the lower bound for sequence correlations that arises from the proposed algorithm framework. We show that such a lower bound can be closely approached by the newly designed sequences. A two-dimensional extension of the time-delay correlation function is the ambiguity function (AF) that involves a Doppler frequency shift. We give an overview of AF properties and discuss how to minimize AF sidelobes in a discrete formation. Besides good correlation properties, we also consider the stopband constraint that is required in the scenario of avoiding reserved frequency bands or strong electronic jammer. We present an algorithm that accounts for both correlation and stopband constraints. We finally consider transmit beampattern synthesis, particularly in the wideband case. We establish the relationship between a desired beampattern and underlying waveforms by using the Fourier transform. We highlight the increased design freedom resulting from the waveform diversity of a MIMO (multi-input multi-output) system.