Automatic UltraWideband Radar System for Life Detection of Hidden Humans
The ultra-wideband (UWB) is a radio technology which can be used at very low energy levels for short-range high-bandwidth communications by using a large portion of the radio spectrum. In February 2002, the Federal Communications Commission (FCC) gave the permission for UWB to be used for imaging and radar production. The corresponding technology is continuing to be developed furthermore, especially the radar applications of life detection. In various situations, the life-detection system for vital parameter detection is a highly useful and important application. It can be used to search for living objects in collapsed buildings after an earthquake or trapped in buildings on fire, or avalanche victims. It can also be used to monitor patients in clinics or at home where it can provide remote measurements of the parameters of a patient's vital activity without having contact with them. In addition, it can be used by law-enforcement services to search for criminals hiding behind various covers. Consequently, there is a growing demand for remote monitoring appliances of human life detector systems. Unfortunately, most of those researches about life detection do not report that there arise four problems in practical situations. The first problem is that most of the articles also do not describe whether their researches could be used for an automatic system or not. The second problem is the error from obstacle effects. The third problem is that the chest movement is not fixed. The fourth problem is the different intensity of a human chest movement. Those are very important points to take into account especially in rescue operations. The challenges mentioned above are fulfilled with the system presented in this work. The UWB radar setup consists of a sub-nanosecond pulse generator, two wideband antennas and two low noise amplifiers. For a fast, robust and accurate algorithm, digital low pass filters are used to remove the background noise. The effect of human breath on the received signal is computed using the unbiased variance. This method is successful to find the expected data behind the noise. The FIR filtering is used to get the peak and interprets it as the position of a human being. Using the magnitude cycle rate with various numbers of averaged points, the breath frequency is determined easily. The more points used, the closer the frequency is to the real values. The system is used to perform one- and two-dimensional measurements for the position and breath frequency of a person behind a wall. The whole measurement times are less than 12 and 42 seconds respectively. It is also robust against multipath and jamming. The development of a reference breath simulator has been successful to achieve the characteristics of breathing at different angles. These results could be used for rescue operations to find persons quickly. Two setups would complete the sensitive angles. The system could also be used for medical measurement of patients in hospital or at home to get stable life data.
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