An eddy-current type proximity sensor is a non-contact type sensing device to detect the approach of a conductor by increase of equivalent AC resistance of excitation coil due to eddy current loss in the conductor. In this paper, electromagnetic characteristics of the actual proximity sensor are calculated by FEM and the validity of numerical analysis results are studied. Furthermore, two models that has modified magnetic circuit geometry based on the actual sensor are designed and calculated as numerical experiments. Calculated results are shown as enhanced sensing index or electromagnetic characteristics of the modified sensor. In conclusions, knowledge about the magnetic circuit geometry of the sensor is applied for the enhancement of sensing property.

Eddy-current type proximity sensor is a non-contact type sensing device to detect the approach of a conductor by increase of coil resistance due to eddy-current loss. This paper proposes to add the cap-shaped magnetic flux shield at the top of the ferrite core for the actual sensor. In conventional proximity sensors, main magnetic flux path passes through the air between the target conductor and ferrite core. Proposed sensor, in contrast, has closed magnetic circuit geometry. It means that main magnetic flux path is almost completed by the core and the shield. Therefore, it is predicted that flux does not reach the target conductor and it causes debasement of sensing property. However, it is shown that the calculated results by FEM and measured results of sensing property of the proposed sensor is enhanced compared with the actual sensor. This paper quantitatively accounts the electromagnetisms of the proposed sensor from sensing property, flux distributions and eddy-current loss in each part of the sensor body. Moreover, material characteristics for the proposed shield, such as relative permeability and conductivity, are found.

In this study, we propose an accurate range-Doppler analysis algorithm for moving multiple objects in a short range using microwave (including millimeter wave) radars. As a promising Doppler analysis for the above model, we previously proposed a weighted kernel density (WKD) estimator algorithm, which overcomes several disadvantages in coherent integration based methods, such as a trade-off between temporal and frequency resolutions. However, in handling multiple objects like human body, it is difficult to maintain the accuracy of the Doppler velocity estimation, because there are multiple responses from multiple parts of object, like human body, incurring inaccuracies in range or Doppler velocity estimation. To address this issue, we propose an iterative algorithm by exploiting an output of the WKD algorithm. Three-dimensional numerical analysis, assuming a human body model in motion, and experimental tests demonstrate that the proposed algorithm provides more accurate, high-resolution range-Doppler velocity profiles than the original WKD algorithm, without increasing computational complexity. Particularly, the simulation results show that the cumulative probabilities of range errors within 10mm, and Doppler velocity error within 0.1m/s are enhanced from 34% (by the former method) to 63% (by the proposed method).