detection of trapped victims beneath building rubble using

1 -21 © MANTECH PUBLICATIONS 2017. All Rights Reserved

Trends in Microwave Engineering and Technology

Volume 2 Issue 1

Detection of Trapped Victims beneath Building Rubble using

Microwave Life Detection Systems in X Band

S.Alagammal1, R.Bhavani

2

Department of Electrical and Electronics

Mepco Schlenk Engineering College, Sivakasi,

Tamilnadu, India

Corresponding Authors: [email protected], [email protected]

Abstract

Nowadays, the awareness about the need of an hour is to find an effective method for rescuing

people buried under earthquake rubble or collapsed building. It is essential one because the

prediction of the occurrence of next earthquake in any parts of the world cannot be known. The

main objective of this task is to identify and discriminate the human under debris among other

things. In this work, a microwave beam of certain frequency (L or S band or UHF band) is

applied to penetrate and reach at a portion of rubble or collapsed building under which a

person has been trapped. Whenever the microwave beam has reached, the reflected waves

comes back which will get modulated or changed based on the person’s movements including

heart beat and breathing and also from the other objects under the collapsed structure. In this

work, by making proper analysis according to the signals received, the identification and the

status of the person can be easily distinguished; thereby the live persons can be safely rescued

from debris anywhere and at any time. By advent of this system the world death rate may

decrease to greater extent as large percentage of death occur due to earthquake.

Keywords: Microwave life detection system, X band, Breathing & Heartbeat signals, earthquake

rubble, FFT Analysis

2 Page 1-21 © MANTECH PUBLICATIONS 2017. All Rights Reserved


Volume 2 Issue 1

1. INTRODUCTION

In general, most of the techniques has been

employed for the detection of living people

buried beneath collapsed building debris

make use of seismic or acoustic equipment,

optical devices or search dogs. Initially dogs

were used to detect presence of human then

acoustic detectors and robot radar come into

existence. However, the dog found only

dead persons which takes more valuable

time of the rescue team. Also, the optical

devices have a limited number of degree of

freedom, require expert operators and

cannot be used in inaccessible area.

Acoustical detectors such as geophones are

simple to use but they require quiet working

environments, a condition difficult to reach

especially in critical situations. But these

systems are having major drawbacks On the

other hand, these methods fail to deliver

reliable detection, especially when the

trapped person fell to unconscious and is

unable to respond.

In addition, the wastage of time will exist

which will be used for the search of further

victims. Besides information about the

location of the buried person would be of

great value for the rescue personnel, since it

will reduce the functional time and thus help

to save more lives.

To organize rapid rescue operations,

emergency forces required timely

information on the exact position of people

trapped or buried under rubble all over the

world, information about collapse of debris

and standardized intervention procedures as

well as information on the state of the

victims health.

Fall down of man-made structures such as

buildings, houses and bridges; this is

occurring with varying frequency across the

world. In such situation, people survive are

usually trapped in the cavities created by

collapsed building material. The concept of

microwave life detection system was

emerged with the development in the

systems for rescue operation.

Initial dogs were used to detect presence of

human then acoustic detectors and robot

radar come into existence. But these

systems are having major drawbacks. In

radar system a SAW oscillator is used to

generate 10GHz frequency signals. While

receiving through patch antenna the signal

is process by the ICA (Independent

Component Algorithm) [1].The history of



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“Revolutionary System to detect Human

Being Buried under the Rubble” starts with

K. M. Chen who brings out the concept of

detection of buried victims using microwave

beam in 1988 [7]. In radar system a SAW

oscillator is used to generate 10GHz

frequency signals. While receiving through

patch antenna the signal is process by the

ICA (Independent Component Algorithm)

[2].

A microwave life detection system operated

on radio frequency was proposed in 1985

[3]. An Ultra-Wideband Radar Concept for

the detection of buried victims beneath

building rubble was proposed in 2010[2]

The phase change of a reflected microwave

signal will provide the precious information

about the buried victim‟s heartbeat as well

as breathing [4].

It states that short wavelength of band

increases the sensitivity of antenna which

will detect the small body vibration [2]. A

rescue radar system is proposed by M.

Donelli in 2011. The researcher put their

efforts to study the various effects of

various bands of microwave signals and

depending upon this, finally system which

detect human being with ka-band with

double sidebands in 2006.

It states that short wavelength of band

increases the sensitivity of antenna which

will detect the small body vibration [4]. The

phase change of a reflected microwave

signal will provide the precious information

about the buried victim’s heartbeat as well

as breathing [3].

2. OVERVIEW OF THE PROJECT

Microwaves are introduced as an

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.

In all cases, microwave includes the entire

SHF band (3 to 30 GHz, or 10 to 1 cm) at

minimum, with RF engineering frequently

putting the lower boundary at 1 GHz (30

cm), and the upper approximately 100 GHz

(3mm).

The microwave life detection system can

works on different range of frequencies

from L-band (2GHz) to X- band (10GHz).

For this reason, the microwave life detection

system which operates on the X-band



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frequency has been implemented. In this

work, a microwave life detection system has

been developed to remotely detect the

signals of human objects lying on the

ground at a distance or located behind a

barrier wall.

The basic principle behind the system is to

illuminate the human parts with a low

intensity microwave beam so that the small

amplitude body vibrations due to breathing

and heartbeat of the human subject will

modulate the back scattered microwave

signal. The receiving system extracts this

back scattered signal reflected from the

human parts.

2.1 Functional Description

Fig-1: Basic Block Diagram

RECORDEER UNIT SIGNAL

PROCESSING

ANTENNA SIGNAL

GENERATOR



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The components that were used in this

project model are Klystron Power Supply,

Klystron Tube, and Digital Storage

Oscilloscope.

Now when the microwave beam is generated

from the Klystron tube, and it is propagated

to antenna through the waveguides. The

supply for the Klystron tube is given by the

Klystron Power Supply. The frequency of

generated microwave beam is measured by

using frequency meter. In between, the

isolator is provided to separate the

generation part from the transmitting part.

The circulator is used to offer an antenna

interface for both transmit and receive

system. The horn antenna is used for

transmitting and receiving the microwave

beam. The reflected waves from the various

objects (like humans, rubbles, metal) are

directed towards the crystal diode detector.

From the detector, the output signal is

retrieved and it is given to the Digital

Storage Oscilloscope. Here the signal is

processed by the technique called Fast

Fourier Transform. Then the processed

signal is recorded in the DSO.

Moreover the variation in the amplitude

level of the reflected signal is measured

here. The amplitude level will be different

for different objects and this variation

depends on the input settings. By checking

these values, it can able to judge the

presence of human behinds under the

rubbles. By observing the shape variation in

the FFT waveform, the presence of human

beings under the rubbles can be easily

detected.

For this purpose, a data sheet has been

prepared which contains the details about

the amplitude variation for various objects at

various objects bat various distances for

different input settings.

3. AWR-SOFTWARE ANALYSIS

The same objective has also been

implemented in AWR environment software

which has the advantages of compact, fast

reliable and provides more enhanced output.

It comprises three powerful tools such as

Visual system simulator, Microwave office

and Analog office software. VSS software

enables us to design and analyze end to end

communication systems. The design of the

systems composed of modulated signals,

encoding schemes, channel blocks and

systems level performance measurements.

However, simulations can be performed

using VSS’s predefined transmitters and

receivers or by using structured customized



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transmitters and receivers from basic

blocks.VSS provides a real-time tuner that

allows us to tune the designs and then see

our changes immediately in the data display.

Microwave Office and Analogue Office

software enables us to design circuits

composed of schematics and

electromagnetic (EM) structures from an

extensive electrical model database, and

then generate layout representations of these

designs.

3.1. Design Algorithm

This topic describes the windows, menus

and basic operations for performing the

following tasks in the AWR Design

Environment (AWRDE) suite.

Creating projects to organize and save

your designs

Creating system diagrams, circuit

schematics, and EM structures

Placing circuit elements into

schematics

Placing system blocks into system

diagrams

Incorporating sub circuits into system

diagrams and schematics

Creating layouts

Creating and displaying outputs

graphs

Running simulations for schematics

and system diagrams

Tuning simulations

3.2. Design with Amplitude Modulation

In this project, microwave beam in X-band

range has been used for the detection of

human beings trapped under rubble. There is

no provision to measure such high

frequencies hence DSO acts as a recording

unit. Since, there is a need of modulation for

extracting the output. Therefore amplitude

modulation are used by taking square pulse

as modulating signal and microwave beam

as modulating signal. Then this modulating

signal is transmitted through the transmit

antenna.

While transmitting this signal to receiving

antenna, a noise signal is also added as a

human signs. In order to eliminate this

unwanted signal, reference signal are

generating as modulating signal, this

reference signal is 1800 phase shifted by the

phase shifter for extracting the human signs.

Then this received signal and the phase

shifted reference signal are given to the

adder, and these unwanted signals are

eliminated here.



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After that, the required signal from the adder

will be received as an output. When

travelling along the path, some of the loss

will exist thereby the amplitude level will

gets reduced that has been taken out in

graphic format. The relevant block diagram

and its corresponding waveforms are shown

in fig. (2-3).

Fig-2: Block diagram for amplitude modulation

Fig-3: Output Waveform with modulation



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Brown Color waveform – Actual Noise

Input

Red Color Waveform - Extracted Output

3.3. Design without Modulation

In AWR Design Environment Software,

there is no provision to directly measure the

microwave frequencies. So there is no need

to modulate the microwave beam. It can be

directly transmitted and received the

microwave beam using this software. In

general, the generated microwave is

transmitted through the transmit antenna. In

between the transmitting and receiving

antenna is a noise signal is added as a

human signs. These signals are received by

the receiving antenna.

For eliminating the unwanted signal we are

generating the reference signal as same as

transmitted signal. This reference signal is

1800 phase shifted by the phase shifter for

extracting the human signal. The received

signal and the phase shifted reference signal

are given to the adder, and the unwanted

signals are eliminated here. The output from

the adder will give the required signal. Due

to the path loss there will be a reduction in

the amplitude level and the output is taken

out in graphic format as shown in Fig (.4-5).

Fig-4: Block diagram for amplitude without modulation



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Fig - 5: Output Waveform without modulation

Brown Color waveform – Actual Noise

Input

Blue Color Waveform - Extracted Output

4. HARDWARE IMPLEMENTATION

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. This system operating at 9.5

GHz can detect the breathing and heartbeat

signals of human subjects through

earthquake rubble or a construction barrier

of about different distance.

The microwave life detection system has all

the components as shown in fig 6.

They are a microwave circuit which

generates, amplifies and distributes

microwave signals to different microwave

components. A dual antenna system, which

consists of two antennas, energized

sequentially. A microwave controlled clutter

cancellation system, which creates an

optimal signal to cancel the clutter from the

rubble. The experimental set up was shown

in fig.7.



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Fig-6: Proposed Block Diagram

Fig-7: Microwave Test Bench

4.1. Klystron Power Supply

The Klystron power supply is used to give

the input to the klystron tube. In addition to

AM and FM modulation of beam current, a

provision for externally modulating the

klystron supply with desired signal

waveform has been provided.



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Table 1 Specifications

Input Voltage 230V AC, 10%, 50Hz

Beam Supply Voltage -250 to -350 V DC

Beam Supply Variable Current 0-50 mA

Repeller Supply 6.3 V DC

Filament Supply 6.3 V DC

Over load Trip Current 65 mA

Modulation Internal, square wave 800- 2000 Hz with

variable frequency and amplitude

Display Digital display for Beam Voltage, Beam

Current and Repeller Voltage.

4.2. Klystron Tube

Reflex Klystron tube is used for the

generation of microwave beam. The

microwave tube uses transmit time in the

conversion of dc power to radio-frequency

(RF) power. The interchange of power is

accomplished by using the principle of

electron velocity modulation and low-loss

resonant cavities in the microwave tube.

Three power sources are required for reflex

Klystron operation: (1) filament power, (2)

positive resonator voltage (often referred to

as beam voltage) used to accelerate the

electrons through the grid gap of the

resonant cavity, and (3) negative repelled

voltage used to turn the electrostatic fields

set up by the resonator potentials (U2) in the

body of the tube. The resonator potential is

common to the resonator cavity, the

accelerating grid, and the entire body of the

tube.



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4.3. Waveguides

The generated microwave bam is propagated

to antenna through waveguides. A

waveguide is a structure which guides

waves, such as electromagnetic waves or

sound waves. The microwave feed from the

antenna is often from through the waveguide

rather than the coaxial cable (or) wires. The

attenuation level is higher in wire and little

lesser in coaxial tube. But in the case of

waveguide, there is no attenuation of

signals. There are different types of

waveguide for each type of wave. The

original and most common meaning ia a

hollow conductive metal pipe is used to

carry high frequency radio waves,

particularly microwaves.

Waves are confined inside waveguide due to

total reflection from the waveguide wall , so

that the propagation inside the waveguide

can be described approximately as a

“zigzag” between the walls This description

s exact for the electromagnetic waves in a

rectangular or circular hollow metal tube.

Hence rectangular waveguides (WR-90),

which is made up of brass/copper material

has been used in this work.

4.4. Horn Antenna

Microwave antenna plays a vital role in

transmitting and receiving microwave

signals which operates above the frequency

of 2GHz in order to meet many technical

and physical requirements. In this work,

Horn antenna is used and its efficiency is

almost 1.

Among many type of horn antenna,

pyramidal type antenna is used, because it

provides the flaring in both electric and

magnetic vector which satisfies all needs.

Horn antenna doesn’t have any resonant

elements; hence they can be operated over

broad band of frequencies.

4.5. Isolator

An isolator is a two-port device that

transmits microwave or radio frequency

power in one direction only. The selection

port is arbitrary, and isolators can be made

to “isolate” either clockwise or counter

clockwise. Isolator is used to improve the

frequency stability of the microwave

generator by using clockwise isolator.

4.6. Circulator

A Circulator is a ferrite device with three

ports also called as a non-reciprocal device.



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A circulator is sometimes called a

“duplexer”, meaning that it is duplexes two

signals into one channel (e.g. transmit and

receive into an antenna). In this work,

clockwise circulator acts as a great antenna

interface for a transmit/receive system.

Energy can be made to flow from the

transmitter (port1) to the antenna (port2)

during transmit, and from the antenna

(port2) to the receiver (port3) during

receive.

4.7. Direct Reading Type Frequency Meter

(DRT)

The calibration in micrometer type

frequency meter is normally provided at 200

MHz intervals, which cannot measure the

small probability in the frequency In this

work, DRT frequency meter has been used

to measure the output signals accurately

which also give direct frequency on the dial

provided.Crystal diode detector unit is a

special adjustable form can be used to

separate the low frequency waves from their

high frequency carrier wave.

5. PERFORMANCE ANALYSIS

A several experiments were performed with

the life detection system with two

parameters also with various objects.

Variation in the amplitude level of square

pulse has been used as an input of rubble or

barrier and the distance between the victim

and the barrier of rubble D was variable

parameter for the experiment.

In this work microwave beams are used for

the detection of trapped victims beneath

building rubbles. According to the

properties, microwave can penetrate through

non metallic objects. But it is completely

reflected by the metal, so that metal has

been selected as a reference object in this

work. Also the changes in reflected waves

for direct metal, direct human and metal

behind rubble and human behind rubble has

been analyzed. In this a wall of 30 x 20 cm2

has been considered as rubble in order to do

analysis.

The microwave frequency of 9.5GHz will be

send as a carrier microwave beam signal

from the klystron power supply, the square

pulse as a message signal along with a

carrier microwave beam are send to the

rubble. The amplitude level of the reflected

waves from the rubble or any other object

has some variations which are used to

distinguish various objects. Thereby the

presence of human beings can be easily

identified and detected which helps to save

their lives.



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Table 2 Data Sheet for various Inputs at two distance level

Object/ Distance

Input = 80 mV

Input =72 mV

Input =148 mV

10cm 20cm 10cm 20cm 10cm 20cm

Direct metal 26.0 mV 19.6 mV 24.0 mV 23.6 mV 58.0 mV 46.0 mV

Direct human 18.0 mV 15.4 mV 14.4 mV 13.2 mV 20.0 mV 18.0 mV

Metal behind rubble 19.6 mV 17.6 mV 16.8 mV 15.2 mV 22.0 mV 19.0 mV

Human behind rubble 16.8 mV 14.56 mV 12.2 mV 10.4 mV 17.4 mV 16.8 mV

For various input settings that the variation

in the amplitude level of square pulse has

been prepared as a data sheet at different

distance level have been shown in table 2

and their respective waveforms are given

below. When the distance increases from 10

cm to 20 cm, the magnitude of the output

signal has been reduced for various objects

are illustrated in table2.

From the table, it is found that, the

variations in amplitude clearly illustrates

that the presence of various objects under

the debris. In addition, for the same distance

like 10 cm, performance of the X band life-

detecting system has been analyzed with the

reflected output waveform is shown in

Fig.8-11.



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Fig-8: Reflected wave by metal at a distance of 10 cm

Fig-9: Reflected wave by metal through rubble at a distance of 10 cm



Volume 2 Issue 1

Fig-10: Reflected wave by Human at a distance 10 cm

Fig-11: Reflected wave by Human through rubble at a distance 10 cm

The microwave beam is applied as an input

to the object directly and indirectly in terms

of voltage at different level. The reflected

received signal is considered as an output

voltage according to the presence of object.

It can be observed that, the output voltage

gets decreased as the distance increases for

the human when compared with other

objects. It can be observed that the

variations in the shape of the output



Volume 2 Issue 1

waveform clearly depict the presence of

human beings trapped under rubbles.

6. FFT ANALYSIS

FFT is a very important mathematical tool

for analyzing and processing the 2D signal,

which also allows time domain signals

processing operations to be performed in the

frequency domain. The plot of amplitude at

different frequency components for a

periodic wave is known as discrete

frequency spectrum. Because amplitude

values have significance only at discrete

values of fo = 2π/T is the spectrum between

two adjacent harmonic components.

In FIR filters, both the hanning and flat top

windows are being designed to optimize the

FFT analysis of continuous signals. In this

flat top windows have been employed to

provide the best estimation of amplitude

variations in the output waveform. The

following figure demonstrates the FFT

waveforms under various conditions.

In the graphs, the heartbeat signal (when the

human subject holding his breath), the

breathing signal, and the background noise

were included. Firstly, the heartbeat and

breathing signals were detected for each

position.

Fig-12: FFT Waveform for complete Reflection by Metal



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Fig-13: FFT Waveform for Reflected Wave by Direct Human

Fig -14: FFT Waveform for Reflected Wave by Human through rubble

Fig.12 to Fig.14 is the Fast Fourier

Transform (FFT) of the time-domain signal,

which shows the frequency components of

the time domain signal. Figures show the

same result performed on the same distance

D for the different objects as shown

respectively. The frequency domain FFT

results show the peaks of heartbeat signal

(0.8 Hz to 2.5Hz) and breathing signal (0.2

Hz to 0.5 Hz). Other small peaks are

probably due to noises or the second

harmonic of the breathing signal. When all

these result were compared it is found that

the amplitude of the breathing signal is



Volume 2 Issue 1

becoming smaller with the increase of the

wall’s thickness.

The heartbeat signal peak also decreases

with the increase of the wall’s thickness. It

can be concluded from the result, thickness

affects breathing signal whereas distance D

affects heartbeats signals. The X band

system performs better enough for remotely

buried victims signals. Our experiments

prove that a buried victim can be efficiently

detected using lower band frequency. Since

wavelength of EM wave is very short,

approximately 3 cm for a carrier frequency

of 10 GHz, the phase of the echo can change

greatly if the target moves even slightly.

Based on this physical behavior the

components of pulse radar system can be

rearranged to work as a life detection

system. This system can operates at 9.5 GHz

and it will be used remotely to detect the

breathing and heartbeat signals of alive

subjects through rubble or some other

barriers about 3ft in thickness.

7. SOCIAL IMPACT

A potential application of this proposed

project is to locate living human subjects

buried in rubble after an earthquake or

avalanche by remotely detecting breath and

heartbeat movements through the barriers.

For detecting and testing health condition of

an individual, they are separated from the

radar by a non-metal wall or in poor

visibility. It could be useful in many critical

services such as medicine, rescue service,

law and antiterrorists enforcements.

8. INFERENCE

In this, the microwave hardware test bench

was developed after conducting a no of

experiments in real time before finalizing

the design work, which reduced the bottle

necks and we did not face much difficulty in

the final integration process. This project

functions in both hardware and software

platform satisfactorily as per the design.

In general, the entire development of the

project work was educative and we have

gained a lot of practical experience by way

of doing the project in all aspects. We could

understand the practical constraints of

developing such systems about which we

have studied by way of lectures in the theory

classes. It was satisfying to see so many

theoretical aspects work before as in real life

practice of which we have heard through

lecturers and of which we have studied in

the books.



Volume 2 Issue 1

CONCLUSION

A new sensitive microwave life-detection

system for locating human subjects buried

under earthquake rubble or hidden behind

various barriers or rubble has been

constructed. This system operating at 9.5

GHz can remotely detect the breathing and

heartbeat signals of living human subjects

through earthquake rubble or a construction

barrier of about various distances. This has

been successfully tested and is found to be

working satisfactorily.

The operation of the system is much more

flexible and easier than others. The

penetration distance can be further increased

by using lower frequency systems (below 1-

GHz). In addition to this, the system has also

been employed in AWR design environment

microwave office software.

In this work, the human signal from the

reflected waves from the rubble has

reasonably extracted and its performance

analysis has been carried out using FFT.

Hence the system is portable. This project is

very helpful for rescue purpose for

government.

FUTURE SCOPE

As for microwave beams vast capability, the

project we have done it is a scratch level

attempt of reaping its benefits. There could

be a lot done using systems, a few which are

listed below illustratively, We can extend

the automatic life detection system by using,

microcontroller. By reducing the frequency

range, we can increase the penetration

capability of the system to detect the victims

beneath rubble. We can develop new

sensitive microwave life detection system,

which can be carried by special rescuing

robots.

REFERENCES

1) M. Donelli, “A rescue radar system

for the detection of victims trapped

under rubble based on the

independent component analysis

algorithm.” Progress In

Electromagnetics Research, M, Vol.

19, 173-181, 2011.

2) C.Labarthe, JP. Mutaig, B. Jecko, H.

Hameih, E. Martinod, N.Feix, J.M.

Lalande, JM. Denoual, JM . Floach,

V. Beetrand, R. Vergnault, “An

Ultra-Wideband Radar Concept for

the detection of buried victims

beneath building rubble”, paper



Volume 2 Issue 1

appears in Radar Conference

(EuRAD), 2010 European.

3) Wu, C. W. and Z. Y. Huang,”Using

the Phase Change of a Reflected

Microwave to Detect a Human

Subject Behind a Barrier” IEEE

Transaction Biomedical Engg, Vol.

55. No. 1, 267-2272, 2008.

4) A. Izadi, Z. Ghatan,” Design and

Simulations of a Life Detection

System based on the Heart Beat

Using Doppler Frequency”, IEEE

International Symposium on Signal

Processing and Information

Technology, 2006.

5) Yanming Xiao; Changzhi Li;

Jenshan Lin; “Accuracy of A Low-

Power Ka-Band Non-Contact

Heartbeat Detector Measured from

Four Sides of A Human Body” Dept.

of Electr. & Computer. Eng., Florida

Univ.,Gainesville, FL, Microwave

Symposium Digest, 2006. IEEE

MTT-S International, June 2006.

6) Huey-ru Chuang, Member, IEEE, Y-

F. Chen, and kun-Mu Chen, Fellow,

IEEE, “Automatic Clutter-Canceller

for Microwave Life-Detection

Systems” IEEE transactions on

instrumentations and measurements,

VOL, 40, NO.4. August 1991.

7) K.M.Chen, Huey-Ru Chuang,”

Measurement of heart and breath

signals of human subjects through

barriers with microwave life

detection system “, IEEE

Eng.Med.Bio.SOC, 10th Annual Int.

Conference, Nov 1988.

Web References

1) Defense Research & Development

Organization

www.drdo.com/pub/nl

2) Geophysical Survey Systems, Inc

www.gssilifelocator.com

Book References

1) Microwave Devices and Circuits by

Samuel Y. Liao. Antenna & Wave

Propagation by K.D.PRASAD.

detection of trapped victims beneath building rubble using

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