Autofocusing method for through‐the‐wall bioradar imagery of human vital signs

In through‐the‐wall human imaging, ambiguities in wall parameters will cause image blurred and deteriorate signal‐to‐clutter ratio of vital signs. Autofocusing method is a kind of method to get focusing image without any information of wall. This method is based on the idea that the focusing performance improves when estimated wall parameters are close to the true parameters. In traditional autofocusing methods, the interesting targets such as the point‐like targets are selected as the reference targets to assess the focusing performance of image. However, in some cases, especially in through‐the‐wall imaging of human vital signs, the existence of human cannot be assured before detection and discrimination. Nevertheless, high‐performance detection of human is the aim of imaging. The wall always exists in the imaging area, and reflections of wall edges are stronger than the interested vital signs. Thus, in this study the authors select the edges of wall as the prominent targets. The linearity degree of wall edges is adopted as the assessment item of focusing performance since the images of wall edges after compensating the wall parameters are lines approximately. Simulation results show that the proposed autofocusing method can effectively improve the focusing performance of human vital signs.