Target Micro-signal Detection Study

Through the wall Surveillance(TWS) now plays more and more important role in various occasions like military operations, counterterrorism, hostage-rescue and earthquake. One outstanding feature that make TWS different from traditional ones is the detection of micro-tremor signals.Ultrasonic is a prospering and widely applied technology, which is known as low-interruption, the capability of detection and low detecting cost. In micro-tremor detection, although ultrasonic is less mature than electromagnetic, its simplicity, convenience and low cost are of a certain research value.This thesis first introduces relevant sound wave knowledge of acoustic pressure, acoustic intensity, acoustic energy, density of acoustic energy, and velocity of acoustic, then analyzes and stimulates reflection and transmission characters of acoustic waves, comparing them with electromagnetic waves to find the competitive advantages of acoustic wave in different occasions. In the second part, this thesis illustrates classification, working principle, and structure of different kinds of ultrasonic sensors, concurrently analyses equivalent circuit, characteristic parameters and measures characteristic group in the experiment and redesigns transmitting and receiving circuits whose distortion is very small referring to the characteristic of detecting micro-tremor signals. Finally, this thesis samples and analyzes the echo signals. Through digital mixing frequency, filter, FFT calculation, we get the feature of the micro-tremor signals which validates the capacity of ultrasonic detection.