Control of orbital angular momentum (OAM) offers the potential for increases in control and sensitivity for high-performance microwave systems. EM waves with properties dependent on spatial distribution are said to be “structured.” Control of OAM in microwave systems is an example of a wave structure that exploits EM degrees of freedom, which most conventional systems do not use. OAM is characterized by an integer OAM mode in which zero represents the case of a plane wave and nonzero OAM modes propagate with a helical wavefront. A uniform circular phased array approach is utilized to produce helix-shaped OAM wavefronts. This method offers a critical advantage over common fixed-frequency dielectric lenses; the phases of all antenna elements are programmable across a wide frequency range, which is necessary for ultrawideband (UWB) radar imaging. Simulations and laboratory experiments are performed to determine the requirements and capabilities of an UWB OAM radar that uses the circular phased array approach. Key results include OAM phase front characterization, detection of specified OAM modes, and configuration of a network analyzer UWB radar with synthetic OAM mode-control via signal post-processing.

中文翻译：

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合成超宽带轨道角动量雷达

轨道角动量（OAM）的控制为高性能微波系统的控制和灵敏度提高提供了潜力。具有取决于空间分布的特性的电磁波被称为“结构化的”。微波系统中OAM的控制是利用EM自由度的波结构的一个示例，而大多数常规系统都没有使用EM自由度。OAM的特征在于整数OAM模式，其中零表示平面波的情况，非零OAM模式以螺旋波前传播。利用均匀的圆形相控阵方法来产生螺旋形的OAM波前。与普通的固定频率介电透镜相比，该方法具有关键优势。所有天线元件的相位都可以在很宽的频率范围内进行编程，这对于超宽带（UWB）雷达成像是必不可少的。执行仿真和实验室实验以确定使用环形相控阵方法的UWB OAM雷达的要求和功能。关键结果包括OAM相前表征，指定OAM模式的检测，以及通过信号后处理进行合成OAM模式控制的网络分析仪UWB雷达的配置。