Doppler-Tags with Self-Interference Cancellation for High-Accuracy Chirp Sequence Radars (DoSIS)

提出了一种能量有效的多普勒标签作为雷达标签，并结合线性调频序列雷达系统，利用信号相位来达到带宽相关值以上的高精度。该多普勒标签向从该对象反射的雷达信号引入了被标记的感兴趣对象的人工多普勒频移特性。雷达信号在标签处被接收，与作为人工多普勒的频率混合，并被送回雷达传感器的方向。在对原始雷达数据的处理中，可以高精度地估计被标记目标的速度和距离。这里需要速度估计来校正影响距离估计的相位误差。识别后对信号中的人为多普勒频移进行校正。在去除多普勒频移之后，沿线性调频样本的线性调频Z变换可以给出第一个粗略的距离估计。这被用作在由频率分析确定的距离区间内进行基于相位的距离估计的起点。这个面元内的高精度范围是使用相位偏移来确定的，其中主要的挑战是对二次相位项的充分抑制。另一个需要考虑的关键方面是自我干预。即使标签的接收和发送通道是分开的，发送信号也将有限地泄漏到接收器中，这将以预期的多普勒频移的两倍产生音调。这可能会对雷达的整体性能产生重大影响，因为泄漏信号不仅可能使接收器饱和，而且可能在再次与多普勒频率混合后产生错误的目标信号，这可能会淹没感兴趣的实际信号。为了克服这一限制，我们将研究通过自干扰消除阶段来增强所提出的标签体系结构。该抵消路径中的延迟必须等于从Tx到Rx天线的耦合路径中的延迟。这种方式与其他措施相结合，例如优化接收和发射天线的布置和设计，可以最大限度地减少干扰对标签性能的影响。通过从接收信号中减去具有正确延迟、相位和幅度的内部泄漏信号，不需要的外部泄漏信号将被消除。这种抵消的质量很大程度上取决于将内部抵消路径精确调整到外部耦合路径的能力。这里，需要可变延迟线。最后，如果不仅使用单个标签，而且将每个对象的多个标签与多传感器设置结合使用，则能够以高精度确定3D中的对象方向。对于设想的应用，重要的是标签具有低能量预算并且它们高度小型化。因此，我们将研究一种基于IC的60 GHz解决方案。

An energy efficient Doppler tag is proposed as radar tag together with a chirp sequence radar system exploiting the signal phase to reach high accuracy above the bandwidth related value. The Doppler tag introduces an artificial Doppler shift characteristic for the tagged object of interest to the radar signal reflected off this object. The radar signal is received at the tag, mixed with a frequency acting as artificial Doppler, and sent back in direction towards the radar sensor. In the processing of the raw radar data, the velocity and range of the tagged object are estimated with high accuracy. Here, the velocity estimation is required to correct phase errors that would affect the range estimation. The artificial Doppler shift is corrected in the signal after identification. After the removal of the Doppler shift, a chirp Z-transform along the samples of the chirp can give a first, coarse range estimate. This is used as starting point for the phase-based range estimation within the range bin determined by the frequency analysis. The high-accuracy range within this bin is determined using the phase offset, where the main challenge is the sufficient suppression of quadratic phase terms. Another critical aspect to consider is self-interference. Even if the receive and transmit channels of the tag are separated, there will be a finite leakage of the transmit signal into the receiver, which will generate a tone at twice the intended Doppler shift. This will potentially have a significant impact on the overall radar performance, as the leakage signal may not only saturate the receiver, but could also create wrong target signatures after being remixed with the Doppler frequency again, that could potentially swamp out the actual signal of interest. To overcome this limitation, we will investigate enhancing the proposed tag architecture by a self-interference cancellation stage. The delay in this cancellation path has to be equal to the one from the coupling path from the Tx to the Rx antenna. This way, combined with additional measures, such as optimized placement and design of the receive and transmit antennas, the impact of interference on the tag performance can be minimized. By subtracting the internal leakage signal with the correct delay, phase and amplitude from the receive signal, the unwanted external leakage signal will be cancelled. The quality of this cancellation strongly depends on the ability to accurately adjust the internal cancellation path to the external coupling path. Here, variable delay lines are required. And finally, if not only a single tag but multiple tags per object are used in conjunction with a multi-sensor setup, the determination of the object orientation in 3D can be enabled with high accuracy. For the envisioned application, it is important that the tags have a low energy budget and they are highly miniaturized. Therefore, we will investigate an IC-based solution at 60 GHz.