Microstrip Patch Antenna Array for Microwave Life Detection System

The antenna system is an integral part of life rescuing system. Rapid developments in wireless communication go in parallel with advancements in compactness and efficiency of antennas. This paper proposes the design of a single element microstrip patch antenna for a microwave life detection system at 1.150 GHz. The patch antenna was simulated in AWRDE Microwave office. A 1×4 patch antenna array was also designed and simulated in AWRDE Microwave office. The simulated results show that the 1×4 patch antenna array has an improved directivity than the single patch. RF communication systems are the most promising area of interest for modern day communication engineers, antenna design being an important part of it. The revolutionalising fact is that antennas, can now-a-days be easily integrated so that they are also compatible with ICs used in RF communication. Microwave life detection systems are effective in searching for human beings trapped under earth quake rubbles even 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. Microwave life detection system work in the L or X band. Since L band microwave signal penetrate large distance and is less affected by the presence of moisture compared to X band, it is better to use L band for life detection . Microstrip patch antennas have low cost, light weight, compact and are easily integrable. Microwave life detection systems have been realized using microstrip patch antenna . Rapid developments in wireless communication go in parallel with advancements in compact and efficient antennas. This paper proposes the design of a microstrip patch antenna array for a life detection system to operate at 1.150GHz (L Band) , using AWRDE Microwave Office. These antennas can also be used for various other applications in L band as WLAN, RF ID systems and other sensors. The basic principle of microwave life detection system is to illuminate the human subjects with a low intensity microwave beam so that, the small amplitude variations due to the breathing and heart beat will modulate the back scattering wave from which the breathing and heartbeat signals can be extracted by phase detection in the microwave receiving system. The potential application of this system is to locate living human or non human subjects buried in rubble after an earthquake, by remotely detecting breath and heartbeat movements through the barrier . The behavior of backscattered field from the vibrations of the body surface caused by the heartbeat and respiration when illuminated by an EM plane wave has been studied assuming that body has the geometry of sphere or cylinder and the phase variation in the backscattered wave is analyzed. Microwave signals at 1.150GHz frequency penetrates through a thickness of 3 meter (10ft) whereas a 10GHz (X band) signal penetrate only 0.5 meter (1.5ft) thickness. So the microwaves of L or S band frequency can penetrate the rubble with metallic mesh easier than that of X band frequencies. So a low frequency signal will penetrate the rubble more and it is used for the microwave life detection system

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