Sensitivity and performance of homodyne radar are notably improved if the phase noise terms of transmit and receive signals are correlated and canceled out by the receiver. However, in a bistatic setup with separate oscillators, this correlation is inherently not given. To achieve a good carrier phase and phase noise coherency, it is required to transmit a radio frequency (RF) reference, e.g., by using high-quality RF cables, optical fibers, or wireless point-to-point links. All these options are complex, costly, and prone to distortions and signal delay variations. Sharing a clock signal is also barely helpful since even small distortions of this reference are converted to notable uncorrelated phase noise in the radar signal synthesizers. In this article, a novel full-duplex system concept and signal processing scheme is presented that solves the above-mentioned problems completely. This concept allows for coherent measurements within a bistatic radar setup, even if the two radar stations are only loosely coupled employing a simple clock-rate adjustment. By theory and experimental results with bistatic frequency-modulated continuous-wave radar, it is shown that our concept allows for bistatic measurements with the same sensitivity and performance that is usually only known from homodyne radar systems. To the authors’ best knowledge, this is the first time that phase noise coherent measurements in a bistatic multiple-input multiple-output radar setup are shown. This concept paves the way for advanced netted radar setups, e.g., in automotive radar and applications with large apertures or baselines or multiperspective coherent tomographic measurements.

中文翻译：

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松耦合双基地雷达的相干信号处理

如果发射和接收信号的相位噪声项被接收机相关并抵消，则零差雷达的灵敏度和性能将得到显着提高。然而，在具有单独振荡器的双基地设置中，这种相关性本质上是不存在的。为了实现良好的载波相位和相位噪声相干性，需要传输射频 (RF) 参考，例如，通过使用高质量的 RF 电缆、光纤或无线点对点链路。所有这些选项都很复杂、成本高昂，并且容易出现失真和信号延迟变化。共享时钟信号也几乎没有帮助，因为即使是此参考的微小失真也会在雷达信号合成器中转换为显着的不相关相位噪声。在本文中，提出了一种全新的全双工系统概念和信号处理方案，彻底解决了上述问题。这个概念允许在双基地雷达设置内进行相干测量，即使两个雷达站只是采用简单的时钟速率调整松散耦合。通过双基地调频连续波雷达的理论和实验结果，表明我们的概念允许双基地测量具有通常仅从零差雷达系统已知的相同灵敏度和性能。据作者所知，这是第一次显示双基地多输入多输出雷达设置中的相位噪声相干测量。这个概念为先进的网状雷达设置铺平了道路，例如，