Life Detection System Based on L and S Band Microwaves

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The "Life detection system : Based on L and S bands Microwaves" is a new revolutionary embedded system to detect human beings buried under earthquake rubble or debris. "Thousands of persons killed as a cause of earthquake". The above words aren’t the headlines of the newspaper but daily news everyone come across whenever we go through a newspaper or watching over a TV news. With the meteoric embedded systems along with microprocessor preventing deaths and providing safe guided measures. By advent of this system the world death rate may decrease to greater extent as large percentage of death occur due to earthquake. The advantages of microwave signals are fully utilized in this system.The L and S band microwaves are used here to detect the living body.

Why Microwave Based Life Detection?

A new sensitive microwave life-detection system which can be used to locate human subjects buried under earthquake rubble or hidden behind various barriers has been constructed. By advent of this system the world death rate may decrease to greater extent as large percentage of death occur due to earthquake. This system operating at 1150 MHz or 450 MHz can detect the breathing and heartbeat signals of human subjects through an earthquake rubble or a construction barrier of about 10-ft thickness. Previous methods for searching and rescuing human victims buried under earthquake rubble or collapsed building debris were the utilization of dogs, or seismic or optical devices. These 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.

What is Microwave?

Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. This broad definition includes both UHF and EHF (millimeter waves), and various sources use different boundaries.

Microwave spectrum

In all cases, microwave includes the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum, with RF engineering often putting the lower boundary at 1 GHz (30 cm), and the upper around 100 GHz (3mm).

Advantages of Microwave

  • Increased bandwidth availability (1 GHz-103 GHz).
  • Improved directive properties.
  • Transmitter /receiver power requirements are very low.

How Microwave Based Life Detection System Works

A phase-locked oscillator generates a very stable EM wave at 1150 MHz with an output power of 400mW(25.6 dBm). This wave is fed through a 10-dB directional coupler and a circulator before reaching a radio-frequency (RF) switch, which energized the dual antenna system sequentially. The 10-dB directional coupler branches out one-tenth of the wave (40 mW) which is then divided equally by a 3-dB directional coupler. One output of the 3-dB directional coupler (20 mW) drives the clutter cancellation circuit and the other output (20 mW) serves as a local reference signal for the double-balanced mixer.

For more details about the implementation, circuitry, modulation and demodulation please refer the attached documents.


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