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

提出了一种高能效的多普勒标签作为雷达标签，结合一种利用信号相位达到高于带宽相关值的高精度的啁啾序列雷达系统。多普勒标签引入了一个人工多普勒频移特性，用于标记感兴趣的目标，以反射该目标的雷达信号。雷达信号在标签处被接收，与人工多普勒频率混合，并向雷达传感器方向发送。在原始雷达数据的处理中，对被标记目标的速度和距离进行了高精度估计。在这里，速度估计需要修正相位误差，相位误差会影响距离估计。经识别后，对信号中的人工多普勒频移进行校正。在去除多普勒频移后，沿着啁啾的样本进行啁啾z变换可以给出第一个粗略的距离估计。这被用作频率分析确定的范围内基于相位的距离估计的起点。该桶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扰。即使标签的接收和发射通道是分开的，发射信号也会有有限的泄漏到接收器中，这将产生一种两倍于预期多普勒频移的音调。这可能会对雷达的整体性能产生重大影响，因为泄漏信号不仅会使接收机饱和，而且在与多普勒频率重新混合后还可能产生错误的目标特征，这可能会淹没实际感兴趣的信号。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结构。这个抵消路径上的延迟必须等于从Tx到Rx天线的耦合路径上的延迟。这样，结合额外的措施，如优化放置和设计的接收和发射天线，干扰对标签性能的影响可以最小化。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，可以消除不需要的外部泄漏信号。这种抵消的质量很大程度上取决于能否准确地将内部抵消路径调整为外部耦合路径。这里需要可变延迟线。最后，如果每个物体不仅使用一个标签，而且使用多个标签，并结合多传感器设置，则可以高精度地确定3D物体的方向。对于预期的应用，标签具有低能量预算和高度小型化是很重要的。因此，我们将研究基于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.