ABSTRACT
“Thousands of people 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 a TV news.
A person’s life is precious and meaningful to his loved ones.
We, as responsible engineers felt a part of society to bring a system to avoid these mishaps. With the meteoric Embedded Systems along with microprocessor our designed system in preventing deaths and providing safe guided measures.
A new revolutionary microwave life detection system which is used to locate human beings buried under earthquake rubble has been designed.This system operating at certain frequency can remotely detect the breathing and heartbeat signals of human beings buried under earthquake rubble.By proper processing of these signals, the status of the person under trap can be easily judged. The entire process takes place within a few seconds as the system is controlled by the microprocessor (8085) or microcontroller unit.
By advent of this system the world death rate may decrease to greater extent as large percentage of death occur due to earthquake? We welcome and wish you to a safe journey of this paper.
INTRODUCTION:
At present as we all know the need of the hour is to find an effective method for rescuing people buried under earthquake rubble or collapsing building. It has to be done before we experience another quake. Present methods for searching and rescuing victims buried or tapped under earthquake rubble are not effective. Taking all the factors in mind, a system which will be effective to solve the problem has been designed
PRINCIPLE OF OPERATION:
The basic principle is that when a microwave beam of certain frequency (L or S band or UHF band) is aimed at a portion of rubble or collapsed building under which a person has been trapped, the microwave beam can penetrate through the rubble to reach the person.
When the person is focused by the microwave beam, the reflected wave from the person’s body will be modulated or changed by their movements, which including breathing and heart beat. Simultaneously, reflected waves are also received from the collapsed structures.
So, if these reflected waves from the immovable debris are cancelled and the reflected wave from the person’s body is properly distinguished, the breathing and heart beat signals can be detected.
By proper processing of these signals, the status of the person under trap can be easily judged. Thus a person under debris can be identified.
MAJOR COMPONENTS OF THE CIRCUIT:
The microwave life detection system has four major components.
They are
1. A microwave circuit which generates, amplifies and distributes microwave
Signals to different microwave components.
2. A microwave controlled clutter cancellation system, which creates an
Optimal signal to cancel the clutter from the rubble.
3. A dual antenna system, which consists of two antennas, energized
Sequentially.
4. A laptop computer which controls the microprocessor and acts as the
Monitor for the output signal.
WORKING FREQUENCY:
The frequency computer of the microwave falls under two categories , depending on the type and nature of the collapsed building. They are
1. L or S band frequency says 1150 MHZ
2. UHF band frequency says 450 MHZ
Let us see the advantages and disadvantages of both the systems later.
PHASE LOCKED OSCILLATOR:
The phase locked oscillator generates a very stable electromagnetic wave say 1150 MHZ with output power say 400 mW.
DIRECTIONAL COUPLER 1(10 DB):
This wave is then fed through a 10 dB directional coupler and a
Circulator before reaching a radio frequency switch, which energizes the dual antenna system. Also, the ten dB directional coupler branches out one-tenth of the wave (40 mW ) which is then divided equally by a directional coupler2(3dB).
DIRECTIONAL COUPLER2(3dB) :
One output of the 3 dB directional coupler2 (20mW) drives the clutter cancellation unit. Other output serves as a local reference signal for the double balanced mixer.
ANTENNA SYSTEM :
The dual antenna system has two antenna, which are energized sequentially an electronic switch. Each antenna acts separately.
CLUTTER CANCELLATION UNIT:
The clutter cancellation unit consists of
1. A digitally controlled phase shifter I
2.A fixed attenuator
3. A RF amplifier
4. A digitally controlled attenuator
WORKING:
CLUTTER CANCELLATION OF THE RECEIVED SIGNAL:
1. The wave radiated by the antenna I penetrates the earthquake rubble
to reach the buried person .
2. The reflected wave received by the antenna2 consists of a large
reflected wave from the rubble and a small reflected wave from the
person’s body.
3. The large clutter from the rubble can be cancelled by a clutter
canceling signal .
4. The small reflected wave from the person’s body cannot be cancelled
by a pure sinusoidal canceling because it is modulated by their movements.
5. The output of the clutter cancellation circuit is automatically
adjusted to be of equal amplitude and opposite phase as that of the
clutter from the rubble .
6. Thus, when the output of the clutter cancellation circuit is
combined with the directional coupler3 ( 3 dB ), the large clutter
from the rubble is completely cancelled
7. Now, the output of the directional coupler3 (3dB) is passed
through a directional coupler4 (6dB)
8. One-fourth of the output is directed is amplified by a RF
pre-amplifier and then mixed with a local reference signal in
a double balanced mixer.
9.
10. When the settings of the digitally controlled phase shifter and the attenuator are swept the microprocessor control system, the output of the microwave detector varies accordingly.
DEMODULATION OF THE CLUTTER CANCELLED SIGNAL:
1.At the double balanced mixer, the amplified signal of the reflected wave from the person’s body is mixed with the local reference signal.
2. The phase of the local reference signal is controlled by another digitally controlled phase shifter2 for an optimal output from the mixer.
3. The output of the mixer consists of the breathing and heart beat signals of the human plus some unavoidable noise.
4. This output is fed through a low frequency amplifier and a band pass filter (0.4 HZ) before displayed on the monitor .
5. The function of the digitally controlled phase of the local reference signal for the purpose of increasing the system sensitivity.
6. The reflected signal from the person’s body after amplification by the pre-amplifier is mixed with the local reference signal in a double balanced mixer.
MICROPROCESSOR CONTROL UNIT:
The algorithm and flowcharts for the antenna system and the clutter cancellation system are as follows :
ANTENNA SYSTEM:
1. Initially the switch is kept in position1 i.e Signal is transmitted through the antenna1
2. Wait for some predetermined sending time ,Ts
3. Then the switch is thrown to position2 i.e Signal is received through the antenna2
4.Wait for some predetermined receiving time Tr
5. Go to step 1
6. Repeat the above procedure for some predetermined time, T.
CLUTTER CANCELLATION SYSTEM:
1. Send the signal to the rubble through antenna1.
2. Receive the signal from the rubble through antenna2.
3. Check the detector output .if it is within the predetermined limits go to step5.
4. Otherwise send the correction signal to the digitally controlled phase shifter1 and the attenuator and go to step1.
5. Check the sensitivity of the mixer. If it is optimum go to step 7 .
6. Otherwise send the correction signal to the digitally controlled phase shifter2 to change the phase and go to step1.
7. Process the signal and send it to the laptop.
No comments:
Post a Comment