摘要：Pulse echo ranging is a method for distance measuring, this method is usually using ultrasound or microwave media, and it has been widely used in many applications. To determine whether an object is moving, it can be seen in the distance changes between the object and the source. However, this method have a major limitation, which is it can only measure the distance to the nearest object, it can not detect other objects around behind that nearest object. In this paper we will discuss the motion detection method that similar to pulse echo ranging, it's just that we are going to compare the echo pattern rather than comparing distance between object and the source. Measurement performed by comparing two echoes pattern with a certain time interval, and the interval between certain pattern of objects’s echoes. And if there are any objects motion in the surrounding sensor area then the echoes patterns will not be exactly in the same shape. With echo pattern comparison method , the sensor is not only sensitive to movement or position changes on the nearest object, it also sensitive to any objects movement in it’s detection area. In practice, echo pattern comparing method has been able to detect human body movements such as human walking, sitting, talking, even it can detect body movement caused by human breathing.
