Buried Bodies Detection Using Ground Penetrating RADAR
Introduction: Existing methods for searching and rescuing human victims buried under earthquake rubble or collapsed building are the utilization of dogs, or seismic or optical devices.
These existing devices are not effective if the rubble or debris covering the human victims is thicker than a few feet, especially for the case when the victims are completely trapped or too weak to respond to the signal sent by the rescuers. Moreover, it is time consumed process. We can lose human life due to this slow process. Thus, there is great demand for constructing a new sensitive life detection system which can be used to locate human victims trapped deep under earthquake rubble or collapsed building debris and quickly. Especially, the system needs to be sensitive enough to detect the breathing and heartbeat signals of passive victims who are completely trapped or too weak to respond to the existing seismic detection system. The basic physical principle for the operation of a microwave life detection system is rather simple. When a microwave beam of appropriate frequency (L or S band) is aimed at a pile of earthquake rubble or collapsed building debris under which a human subject is buried, the microwave beam can penetrate through the rubble or the debris to reach the subject. When the human subject is illuminated by the microwave beam, the reflected wave from the subject will be modulated by the subject’s body movements, which include the breathing and the heartbeat. If the reflected wave from the stationary background can be cancelled and the reflected wave from the subject’s body is properly demodulated, the breathing and heartbeat signals of the subject can be extracted. Thus, a human subject buried under the rubble or the debris can be located easily and quickly.
Figure 1.1 Pseudo Practical System for Human Life Detection [1]
Implementation: The approach that we will be following throughout the project is to generate microwaves from Phase locked oscillator. This wave will be passed through a directional coupler that would branch out the wave to phase shifter and transmitting antenna. The phase shifter would shift the phase by 180 degrees and will pass it to the Attenuator/Amplifier. The reflected wave would be possessing the information about the target like there will be a Doppler shift in the reflected wave. This reflected wave will then be added to the output of attenuator/amplifier. This would cause the cancellation of the clutter (useless) signal but the modulated signal would reside there that would be passed to microprocessor for processing.
Figure 1.2 Block Diagram for Buried Bodies Detection using GPR
Circuit Description of the System: There are various components for the project that are being used for different purposes as shown in Figure 1.2. The description for each component is following.
Phase Locked Oscillator: The basic purpose of phase locked oscillator is to generate specific frequency. It locks the frequency. Whenever frequency due to error or noise changes , it brings it back to the original frequency. In our purpose, we will be using this component for generating microwave frequency. Frequency generated for Phase Locked Oscillator is accurate enough. That is the main benefit of Phase Locked Oscillator. In our case, we need a signal of microwave frequency. Phase Locked Oscillator will generate this signal with specific frequency. So that if signal gets deviated from its original frequency, then Phase Locked Oscillator will bring it back.
Directional Coupler: The purpose of directional coupler is to split the power of high frequency wave. When there is branch in the circuit, the high frequency components do not go
better in braches. So, Directional coupler does this job better. It splits the frequency into two power components. These both signals go to their separate branch. In our system, as we are transmitting frequency generated by Phase locked oscillator through antenna as well as giving it to the Phase shifter and then attenuator/amplifier. So, here is the branch . We need to add directional coupler here.
Phase Shifter: As the name suggests, phase shifter shifts the signal by some amount. In our case, we will be shifting the signal coming from directional coupler by 180 degree somehow. So that, it will cancel out with the wave coming from receiving antenna. 180 degree in not an accurate value. From practical point of view, there can be phase delay in the receiving signal. So, we have to adjust the phase of phase shifter depending on the phase shifted of incoming signal.
Attenuator/ Amplifier: Incoming Signal from receiving antenna would have been attenuated or amplified due to the environment effect (most probably attenuated). So, we have to cancel it with the original signal that was given to phase shifter. After passing through phase shifter, signal would be amplified or attenuated. So that, It would cancel out the original signal part from incoming signal (through receiving antenna).After cancelling, we would have only the information signal that actually we needed.
Transmitting and Receiving Antennas: Antenna sends out the signal or wave to the environment. As the name suggests, transmitting antenna transmits the signal while receiving antenna receives the signal. It is common device in communication systems. In our case, signal would be sent to the target (alive human) through transmitting antenna. After colliding with the target, it would be modulated signal that would have the information of the target. Receiving Antenna will then receive that signal.
Microprocessor: Microprocessor is also the main part of the system. It would be assuring that the original signal has been cancelled out from the receiving signal. If not then shift the phase or attenuate/amplify the signal such that it will cancel out the original part from incoming signal. This new informative signal will then processed. By the
frequency analysis, we will decide whether there was alive human being or not. If there is, then perhaps it would calculate the distance of the target from the antenna.
Objectives:
Life detection systems under earthquake barrel. Low cost design and hardware implementation. Real time processing of Signals.
Benefits:
This project would prove to be a helpful tool in saving man power and resources as well. In spite of digging up all the way around to search the life signs, if we know about the target’s location it would help a lot in saving the time and more importantly the human life. Detect submarines and other things in water. Detection of stealth aircrafts for military purpose.
References: [1] Yanming Xiao et al., “Frequency-Tuning Technique for Remote Detection of Heartbeat and Respiration Using Low-Power Double-Sideband Transmission in the Ka-Band”, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 54, NO. 5, MAY 2006. [2] Changzhi Li and Jenshan Lin. “Random Body Movement Cancellation in Doppler Radar Vital Sign Detection”, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 56, NO. 12, DECEMBER 2008. [3] Kun-Mu Chen, et al. “Microwave Life-Detection Systems for Searching Human Subjects Under Earthquake Rubble or Behind Barrier”, IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 27, NO. 1, JANUARY 2000. [4] Chen-Chia Wang, et al. “Human Life Signs Detection Using High-Sensitivity Pulsed Laser Vibrometer”, IEEE SENSORS JOURNAL, VOL. 7, NO. 9, SEPTEMBER 2007. [5] Yanyun Xu, et al. “Experimental Study of UWB Pulse Radar for Life Detection”, 2011 International Conference on Instrumentation, Measurement, Computer, Communication and Control. [5] Yanyun Xu, et al. “Experimental Study of UWB Pulse Radar for Life Detection”, 2011 International Conference on Instrumentation, Measurement, Computer, Communication and Control.
WWW. [6] Rebecca Boyle. (August 2, 2010). NEW CORPSE-DETECTION SYSTEM FINDS WHERE THE BODIES ARE BURIED [Online]. Available: http://www.popsci.com/science/article/2010-08/newcorpse-finder-test-knows-where-bodies-are-buried. [7] Lindsay Moran. (April 8, 2014). Buried alive to test new tech [Online]. Available: http://america.aljazeera.com/watch/shows/techknow/articles/2014/4/8/buried-alive-totestnewtech.html
