Millimetre-wave detection device for discriminating between different materials

摘要

A detection device that can be used for detecting objects behind clothing etc includes a receive antenna and a receive element sensitive to millimetre wave radiation along with an internal source of millimetre wave radiation for calibration purposes. Prior art systems produce an image of a scene usually using scanning optics. This can be large and expensive. The present invention instead take spot readings from different parts of a scene without building up an image from the readings. The spot readings are processed, and an indication given to a user if certain characteristics of the readings are observed. Typical characteristics used are the differences in absolute received power level, and the power level at different polarisations. Such characteristics are typically present if an object of interest is in the scene. Also disclosed are various methods of altering the receive beam to get readings from different areas from the scene, such as changing the beam width, or beam angle.