Abstract
It is a major challenge to search for survivors after chemical or nuclear leakage or explosions. At present, biological radar can be used to achieve this goal by detecting the survivor’s respiration signal. However, owing to the random posture of an injured person at a rescue site, the radar wave may directly irradiate the person’s head or feet, in which it is difficult to detect the respiration signal. This paper describes a multichannel-based antenna array technology, which forms an omnidirectional detection system via 24-GHz Doppler biological radar, to address the random positioning relative to the antenna of an object to be detected. Furthermore, since the survivors often have random body movement such as struggling and twitching, the slight movements of the body caused by breathing are obscured by these movements. Therefore, a method is proposed to identify random human-body movement by utilizing multichannel information to calculate the background variance of the environment in combination with a constant-false-alarm-rate detector. The conducted outdoor experiments indicate that the system can realize the omnidirectional detection of random human-body movement and distinguish body movement from environmental interference such as movement of leaves and grass. The methods proposed in this paper will be a promising way to search for survivors outdoors.
Highlights
Rescuing survivors is very difficult because it is not easy for rescuers to arrive at the accident site immediately after an explosion at a chemical factory or a disaster at a nuclear power plant
In a continuous wave (CW) radar system, a sine wave is transmitted to a target, where it is reflected, and the back-reflected wave reaches the receiving antenna with a time difference that depends on the distance to the target, i.e., the phase difference between the transmitted and received signals is directly proportional to the motion of the target
It is difficult to determine whether the detected object has vital signs through human respiration signal recognition since the respiration signal in the radar echo is weak and cannot be acquired
Summary
Rescuing survivors is very difficult because it is not easy for rescuers to arrive at the accident site immediately after an explosion at a chemical factory or a disaster at a nuclear power plant. If the survivors can be found quickly, their rescue and the efficiency at which the wounded are treated will be greatly improved. A thermal infrared camera can detect an object’s temperature, but there is a significant delay in determining whether the detected object has vital signs through the body temperature. It is difficult to reach the detection demand by only using camera detection technology to search for survivors. In order to meet this need, 24-GHz continuous wave (CW) radar is applied to detect humans outdoors
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