A 24-GHz continuous wave (CW) radar with three vertically switched beam antennas for monitoring different range segments has been newly proposed and developed as a means to detect intruders in a fan-shaped ground area with 90 degs. in azimuth and over 10 m in range. This radar can detect moving targets and measure their positions from a tampering-proof height of about 5 m by taking advantage of a two-frequency-CW modulation technique and monopulse scheme used to achieve the wide azimuth coverage. The radar module consists of microstrip-patch planar antennas and monolithic microwave integrated circuits (MMICs), which are placed on the opposite side of a single metal plate to attain compact size and lower cost. An experimental radar successfully detected a human intruder with a position accuracy of 50 cm when moving at 1.4 m/s.

This paper proposes an indoor event detection system for homes and offices that is based on electric wave reception such as intrusion into home or office. The proposed system places antenna array on the receiver side and detects events such as intrusion using the eigenvector spanning signal subspace obtained by the antenna array. The eigenvector is based on not received signal strengths (RSS) but direction of arrival (DOA) of incident signals on the antenna array. Therefore, in a static state, the variance of the eigenvector over time is smaller than that of RSS. The eigenvector changes only when the indoor environment of interest changes intermittently and statically, or dynamically. The installation cost is low, because the detection range is wide owing to indoor reflections and diffraction of electric wave and only a pair of transmitter and receiver are used. Experimental results reveal that the proposed method can distinguish the state when no event occurs and that when an event occurs clearly. Since the proposed method has a low false detection rate, it offers higher detection rates than the systems based on RSS.

The authors propose a method of detecting intruders around power line towers using a new image processing technique. With current technology for outdoor imaging, a varitey of factors may lead to erroneous image processing, such as changes of background brightness, rustling of leaves, mist, rain, intrusion of small animals, etc. These problems were solved as follows. With this method, a change of image, which may indicate an intruder, is first detected using a histogram of the brightness difference between a reference image and an observed image. The detected differences are further analyzed to determine whether they represent a human intruder by evaluating a restraint based on the number, the area, the dimensions of the circumscribing rectangle and the center of gravity of the detected portion. Field testing confirmed the method's usefulness, with a successful intruder detection rate of 82%.