Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
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7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
http://slidepdf.com/reader/full/low-cost-em-signal-direction-estimation-with-two-element-time-modulated-array 1/6
International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013
ISSN: 2231-2803 http://www.ijcttjournal.org Page 2113
Low Cost Em Signal Direction Estimation With Two Element
Time Modulated Array System For Military/Police Search
Operations
B.Gayathri#1
, M.Devendra*2
Department of ECE( M.tech), G.P.R Engg College, Kurnool.
Associate Professor, M.S., (Ph.D), G.P.R Engg College, Kurnool.
ABSTRACT-
Today homeland secuiry could be a huge matter of concern.
The current day wireless technology is accessible to anti-
social components that measure mistreatment this in manyundesirable manners. By knowing the direction of the
source of magnetism waves it becomes possible to find such
anti-social teams and take offensive action. In military
applications additionally finding the direction of the signal
supply becomes valuable information. The direction finding
systems can do this goal.
Conventional radio direction finding (RDF) systems usually
use associate degree array of 2 or additional antennas and
use either phase-comparison or amplitude-comparison of
the received signals to work out direction of arrival data. In
each of those techniques directional data springs by process array information at the receive signal frequency.
In this project, to seek out the direction by mistreatment the
strategy of time-switched array system is enforced. The
time-switched array system uses straightforward signal
process techniques to produce a directional main beam and
pattern nulls at harmonic frequencies. To see 2 dimensional
angles are 3 parts, the system price has been largely
minimised. We have a tendency to currently take into
account the matter of mistreatment our low price system to
find and estimate the direction of arrival of a desired signal within the presence of array antenna.
The projected theme is value effective technique as
compared with the prevailing schemes.
MATLAB/GNU OCTAVE simulation tool are going to be
used for simulation. The simulation results, applications,
deserve and demerits of projected approach are going to be
analyzed and can be documented.
Index Terms-antenna, array, direction finding.
I. INTRODUCTION
Time modulated arrays (TMAs) are unit antenna
systems wherever a group of frequency (RF) switches is
employed within the beam forming network to modulate the
static excitation weights of a standard phased array. The on-
off commutation of the switches are controlled by periodic
pulse sequences, generates harmonics, known as sideband
radiation (SR), that are unit spaced within the frequency
domain by multiple of the heartbeat repetition frequency.
Until today, most of the analysis activities are dedicated to
the synthesis of a desired pattern at the antenna operating
frequency and therefore the joint minimisation of the ability
losses within the SR that incapably cut back the antenna
directionality and gain. During this framework, TMAs are
used to get ultra-low facet lobe patterns and formed beams
with component excitations characterised by reduced
dynamic vary quantitative relation. The synthesis of pulse
Doppler radio location and sum-difference patterns for
monopulse applications has been thought-about, as well.
More modern used instead thought-about the exploitation of
the harmonics generated by the modulation method. Among
them, multiple harmonic patterns directed on totally different
angular directions are used for electronic beam scanning
7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
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International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013
ISSN: 2231-2803 http://www.ijcttjournal.org Page 2114
applications, the estimation of the direction of arrival, and in
psychological feature radio systems.
It has been exploited in numerous applications (e.g., radar,
sonar, wireless communications, seismic exploration, speech
processing, medical imaging, radio astronomy).
0°
90°
12
1
1
2
2
Fig 1: Two Element Time-Switched Array and definition of switching wave
forms.
Time switched array systems
The received signal from every component of the array is
time switching wave and combined to produce a part
modulated output. The shape of the time modulation is said
to each of the switching waves and therefore the direction of
arrival of the incident signal. The angular response at the
primary higher and lower harmonic frequencies exhibits one
deep null which may be scanned in angle over a full ninety
vary by dominant the component shift wave. The time-
switched array so achieves active electronic null steering
while not the necessity for part shift, or time, delays,
network.
An inherent disadvantages associated with time-
modulated arrays is that they generate unwanted harmonics,
or sidebands, at multiples of the change frequency and most
analysis into time-modulated arrays has focused on
minimizing or dominant these harmonics. A lot of recently
work has been administrated to analyze the utilization of part
centre motion to manage aspect lobe levels and therefore the
application of time-modulated arrays in Doppler radio
location.
During this contribution we tend to describe a prototype
2 component time-switched array system and gift measured
knowledge may be the performance of the array.
Direction of Arrival
We have seen that there a matched relationship between the
direction of a signal and therefore the associated received
steering vector. It ought to so be attainable to invert the link
and estimate the direction of a signal from the received
signals. An antenna array so ought to be able to give for
direction of arrival estimation. We’ve got additionally seen
that there's a Fourier relationship between the beam pattern
and (DOA) estimation drawback to be treated as resembling
spectral estimation.
∅∅∅
D
Fig 2: The DOA estimation problem
The problem created is shown in Fig. 1. Many (M) signals
collide with a linear, equispaced, array with N parts, every
with direction φi. The goal of DOA estimation is to use the
information received at the array to estimate φi, i = 1 . . . M.
it's usually assumed that M < N, although there exist
approaches (such as most chance estimation) that don't place
this constraint.
∑
7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
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International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013
ISSN: 2231-2803 http://www.ijcttjournal.org Page 2115
II. SYSTEM DESCRIPTION
The time-switched array system is shown schematically in
Fig.1 and consists of 2 antenna parts separated by a distance
d. every component is assumed to exhibit omnidirectional
radiation within the plane of the diagram. The output fromevery component is connected to the array output via a
switch within the feed line the component change amount is
additionally outlined in Fg.1. a complete analysis the system
is also found and except for the aim of this contribution we'll
going to assume that the weather are alternately switched on
and off with an equal mark-space magnitude relation sq.
wave change perform such t1= t2 = T/2.
If we tend to assume that the spacing between thecomponents is a half wavelength, the output from the array is
also represented by
A (θ, t) = cos,where
={
п θ; ()
;
}.
Time-switched array
Mounted on turntable
Receive antenna
Fig 3: Details of the measurement set-up.
Hence the output of the array is part modulated and
therefore the depth of modulation depends on the angle of
arrival of the incident signal. For illumination broadside to
the array, the array output isn’t modulated. However, because
the illumination angle will increase the depth of modulation
will increase till at finish hearth illumination (θ = 90deg) the
array output exhibits 180 deg part shift modulation. A plot of
the array receive pattern at the example frequency, ω, is
given in Fig.2 and shows a directional response with a peak
on broadside and a null response at ±90deg. The directional
pattern happens as a result of because the depth of PM will
increase energy is decentralized from the carrier into
sidebands, and at finish hearth there's zero energy at the at
the carrier frequency. If we have a tendency to currently
examine the output of the time-switched array at the primary
harmonic.
Multiple Signal Classification Algorithms:
MUSIC is perhaps the foremost standard technique. MUSIC,
as square measure several adaptation techniques, depends on
the matrix of the information. Using
The matrix S may be an N ×M matrix of the M steering
vectors. Forward that the diff erent signals to be uncorrelated,
the matrix of x may be written as
Signalsource
Spectrumanalyzer
7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
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International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013
ISSN: 2231-2803 http://www.ijcttjournal.org Page 2116
Where
The signal variance matrix, Rs, is clearly an N × N matrix
with rank M. It thus has N−M eigenvectors like the zero
eigenvalue. Let qm be such associate eigenvector. Therefore,
Where this final equation is valid since the matrix A is clearly
positive definite. It implies that every one N −M eigenvectors
(qm) of Rs in to the zero eigenvalues are orthogonal. To any
or all M signal steering vectors. This can be the idea for
MUSIC. Decision Qn the N × (N −M) matrix of those
eigenvectors. Note that since the eigenvectors creating up Qn
orthogonal to the signal steering vectors, the divisor becomes
zero once φ may be a signal direction.
BLOCK DIAGRAM
Table1
Algorithm overview
Step1: First we tend to think about AN L formed antenna
array system on the Z axis with the gap of separation aszero.5 λ and letter as 360 deg.
Step2: To calculate the output radiated from the three
antennas.
Step3: Upon calculating the magnitude of the output, we tend
to plot the magnitude (in decibel) against the angle (in deg).
Step4: To calculate the angle of arrival, we find out the peak
value wherever the output is most. The angle of arrivals is
found to be 90 and 270 degrees severally.
step5: we tend to next calculate 2 of the foremost necessary
properties i.e., Array issue and Array part.
step6: we tend to then create polar plots of each Array issue
and Array part with an angle of 360 degrees.
Step7: The last step is to calculate and plot spectral analysis
victimisation MUSIC rule.
Step8: To perform the analysis, we tend to initial produce a
steering vector matrix with the assistance of DOA’s found.
Step9: Generate BPSK symbols and add uncorrelated noise
to the present knowledge to come up with an information
matrix.
Step10: To form a variance matrix and realize all the Eigen
values and Eigen vectors from this matrix.
Step11: Sort these Eigen vectors to separate signal Eigen
vectors in Qs and noise Eigen vectors in Qn.
L shaped 3
antenna
array
Output
radiated
Angle of
arrival
Array element
&array factor
calculation
Spectral analysis
using MUSIC
al orithm
7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
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International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013
ISSN: 2231-2803 http://www.ijcttjournal.org Page 2117
Step12: we tend to then type a steering vector matrix from
every of the angles from one to 360 in a1.
Step13: Finally we tend to plot the spectral values against the
angles in degrees.
A spectrum instrument measures the magnitude of input
signal versus frequency among the complete frequency vary
of the instrument. The first use is to live the ability of the
spectrum of far-famed and unknown signals. The signal a
spectrum instrument measures is electrical, however, spectral
compositions of different signals, like acoustic pressure
waves and optical light-weight waves, may be through the
applicable electrical device. By analyzing the spectra of
electrical signals, dominant frequency, power, distortion,
harmonics, bandwidth, and different spectral elements of an
indication may be determined that don't seem to be simply
detectable in time domain waveforms. These parameters
square measure helpful within the characterization of
electronic devices, like wireless transmitters. The show of a
spectrum instrument has frequency on the horizontal axis and
also the amplitude on the vertical axis. To the casual
observer, a spectrum instrument appears like AN scope and,
in fact, some work instruments will perform either as AN
scope or a spectrum instrument.
Fig 6: Spectral Analysis using MUSIC Algorithm
Fig 7: Measured Angle of Fig Arrival shown at precisely 90 and 270 deg
Fig 5: Array Factor and Array Element
The measured results are plotted in Fg.5 along with
practical predictions obtained from a simple model based on
array factor and array element.
III. CONCLUSION
While in the presence of a two element time-switched
array system has been implemented. The signals to each
element of the array are time switched to provide a phase
modulated output signal in which the depth of modulation is
dependent on the angle of arrival of the received signal. The
angular response to the array at the fundamental frequency of
0 50 100 150 200 250 300 350 400-25
-20
-15
-10
-5
0
5
10Output
Angle (deg)
G a
i n
( d B )
0.5
1
30
210
60
240
90
270
120
300
150
330
180 0
0.5
1
30
210
60
240
90
270
120
300
150
330
180 0
7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search
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International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013
ISSN: 2231-2803 http://www.ijcttjournal.org Page 2118
the received signal exhibits a directional response at
broadside, while the response at the first harmonic of the
switching frequency exhibits a deep null.
REFERENCES
[1] M.J.Wilson and B.S.Halo, the ARRL Handbook for the Radio mateur, 65 th
ed.Washington, DC: American Radio Relay League, 1988.
[2] A.Tennant and B.chambers, “A two-element time-modulated array with
direction finding properties,”IEEE Antennas Wireless propag. Lett, vol. 6,
pp.64-65, 2007.
[3] A.Tennant and B.chambers “Direction finding using a four element. Time-
switched array,” presented at the Loughborough Antennas and propagation
conf, Loughborough, U, K, Mar.17-18, 2008.
[4]H.E.Shanks and R.W.Bckmoree,”Four-dimensional electromagneticradiators, “canard J.phys, vol. 37, p.263, 1959.
[5] W.H. Kummel, A. T. Villenuve,T.S.Fong and F.G. Terrio,”ultra- low side
lobes from time-modulated arrays”IEEE Trans Antennas propag., vol.
11,pp.633-69,1963.
[6] S.Yang, Y.B.Gan,Z, and A. Qing,” Sideband suppression in time-
modulated linear arrays by the differential evolution algorithm,”IEEE
Antennas Wireless Propag.Lett.,vol. 1,pp. 173-175,2002.
[7] S.Yang, Y.B.Gan, and P.k.Tan,”A new technique for Power- pattern
synthesis in time-modulated linear arrays,”IEEE Antennas Wireless propag.
Lett, vol.3, p.298-300, 2004.
Author Biographies
Mr.M.DEVENDRA obtained his
M.S. in Electronics and Control from
BITS Pilani in 1996.He is currently
pursuing Ph.D degree from GITAM
University, Hyderabad, India. He
published 3 papers in International
journals and presented 4 papers in
National conferences and 1 paper in
International conference. He is
presently working as Associate
Professor in ECE Department,
G.Pulla Reddy Engineering, College, Kurnool, India. His research interests
include VLSI and Signal processing.
Ms.B.GAYATHRI is pursuing her
M.Tech in communication and signal
processing(C.S.P) at G.Pulla Reddy
Engineering, College, Kurnool,India. She
published 1 paper in International
conference and 1 paper in national
conference.. Her area of Interests is in the field of Antennas and signal processing.
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