No abstract

For imaging radars, the calibration effort increases with higher frequency and finer angular resolution demands and is therefore one of the largest cost factors in radar production. In case of high angular resolution, the calibration is also sensitive to array misalignment, resulting in costly calibration procedures. This paper proposes an angle-dependent radar calibration method with significantly reduced calibration effort. The high efficiency and robustness against misalignment is achieved by exploiting phase symmetry of a target in the measured radar response. Based on an initial theoretical formulation followed by an experimental verification, this novel approach does not only yield a cost-effective calibration, but also increases the robustness against array misalignment.

Manufacturing uncertainties, antenna coupling, and other hardware imperfections lead to a deviation of the real hardware behavior from the ideal one. Calibration procedures aim to determine the deviation between the ideal signal model and the real hardware behavior to achieve an improved measurement accuracy of the array. When using large apertures and large modulation bandwidths, the measured distance of a single target at different receive antennas depends on the incident angle. Furthermore, the far-field condition cannot be met. In this paper, the influence of these errors on the calibration is analyzed and a strategy to correct these errors by signal processing is derived. Additionally, we propose a method to reduce the calibration effort for large aperture radars based on the a-priori knowledge of the array geometry. Experimental results with an imaging radar at 150 GHz demonstrate the efficiency and accuracy of the proposed error correction method and the related calibration concept.

With radar networks, the resolution of critical radar parameters like Doppler and angle can be improved compared to a single radar sensor. As the network's aperture is considerably larger than the one of a single radar, a much higher angular resolution is achieved. However, with a large aperture, rangedependent phase deviations, i.e. near-field effects, occur and affect the angle estimation. In this work, these near-field effects are evaluated exemplarily for a coherent network. Furthermore, a new strategy to compensate those network near-field effects is proposed and demonstrated based on measurements. The benefits of the near-field compensation are emphasized by comparing the networks angle-estimation capabilities with and without compensated near-field effects.

No abstract