发表机构
Naval Undersea Warfare Center（海军水下作战中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文表征了采用PSK的FM-OFDM波形的频谱与模糊函数特性，基于EOA模型得出三项关键结论，并提出利用部分子载波作为导频优化ACF旁瓣的波形设计方法。
AI 中文摘要
本文对采用相移键控（PSK）的调频正交频分复用（FM-OFDM）波形的频谱特性及模糊函数（AF）进行了表征。该模糊函数的主瓣结构可由模糊椭圆（EOA）模型很好地近似，该模型能生成精确的闭式表达式，用于描述模糊函数在时延和多普勒域的主瓣宽度，以及二者之间的耦合程度。这些表达式为采用PSK的FM-OFDM波形的频谱和模糊函数形状提供了三个基本结论：（1）在给定调制指数h、脉冲时长T和子载波数量L的情况下，这类波形具有固定的均方根（RMS）带宽；（2）在相同均方根带宽下，它们的频谱效率约为恒包络OFDM（CE-OFDM）波形的两倍；（3）对于实际波形设计参数，这类波形始终具有“图钉状”的模糊函数形状。最后，本文展示了一种波形优化技术，该技术仅使用部分子载波符号作为感知“导频”符号，其余子载波符号用于通信，以此最小化FM-OFDM波形的自相关函数（ACF）旁瓣，并通过两个示例设计对该导频优化技术进行了验证。
英文摘要
This paper characterizes the spectral and Ambiguity Function (AF) properties of Frequency Modulated Orthogonal Frequency Division Multiplexing (FM-OFDM) waveforms employing Phase-Shift Keying (PSK). The mainlobe structure of the AF is well approximated by the Ellipse of Ambiguity (EOA) model. The EOA produces exact closed-form expressions that describe the AF mainlobe width in time-delay and Doppler as well as the degree of coupling between them. These expressions yield three fundamental insights into the spectral and AF shapes of FM-OFDM waveforms employing PSK: (1) these waveforms possess a fixed Root Mean Square (RMS) bandwidth for a given modulation index $h$, pulse-length $T$, and number of sub-carriers $L$, (2) they are roughly twice as spectrally efficient as Constant Envelope OFDM (CE-OFDM) waveforms with the same RMS bandwidth, and (3) for practical waveform design parameters will always possess a ``Thumbtack-Like'' AF shape. Finally, this paper demonstrates a waveform optimization technique that minimizes the FM-OFDM waveform's Auto-Correlation Function (ACF) sidelobes using only a subset of the sub-carrier symbols as sensing ``pilot'' symbols leaving the rest for communications. This pilot optimization technique is then demonstrated via two illustrative design examples.
CommentsAccepted for presentation at the IEEE ISAC Conference
