1. INTERNATIONAL JOURNAL OF Issue 2, March – April (2013), ©ISSN 0976 –
International Journal of Electrical Engineering and Technology (IJEET),
6545(Print), ISSN 0976 – 6553(Online) Volume 4,
ELECTRICAL ENGINEERING IAEME
& TECHNOLOGY (IJEET)
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 4, Issue 2, March – April (2013), pp. 105-111
IJEET
© IAEME: www.iaeme.com/ijeet.asp
Journal Impact Factor (2013): 5.5028 (Calculated by GISI) ©IAEME
www.jifactor.com
FEASIBILITY STUDIES OF WIRELESS SENSOR NETWORK AND ITS
IMPLICATIONS
S.R.Shankara, Dr.G.Kalivarathanb
a
Research Scholar, CMJ University, Meghalaya, Shillong.
b
Principal/ PSN Institute of Technology and Science, Tirunelveli, Tamilnadu, Supervisor,
CMJ University, Shillong. Email:sakthi_eswar@yahoo.com
ABSTRACT
WSNs provide endless opportunities, but at the same time pose formidable
challenges. One of the key challenges of wireless sensing applications is that the information
collected by these applications is incomplete. In particular, the amount of usable quality
information collected by the wireless sensing applications is constrained by various limiting
characteristics of the host network. High Temperature Superconductors (HTS) are more and
more present in RF and microwave applications. HTS thin film technology can be used for
high Q resonators and very selective multi-pole filters with very low insertion-loss. In order
to prove the HTS devices feasibility for RF and microwave applications, HTS microstrip
resonators and HTS antennas have been investigated experimentally. The work described is
limited to a few preliminary studies. This is due to the lack of further funding. Most of the
research results performed for this thesis refer to cellular systems, which are the most
prevalent part of terrestrial radio communications. The terrestrial communications include
also cordless telephony, paging, professional mobile radio (PMR). The radio link in a cellular
system is subjected to the specific propagation laws of the radio waves. There is a significant
contrast between a transmission channel of a wired communication path and a radio mobile
channel. Since the former is almost constant in time, the latter is random and undergoes
shadowing and multipath fading. Even when a mobile user is stationary, ambient motion in
the vicinity of the base station can produce fading.
Keywords: High Temperature Superconductors, Professional mobile radio, Finite-Difference
Time-Domain, GSM 900 receivers,
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2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
1.0 INTRODUCTION
A 3-D Finite-Difference Time-Domain (FDTD) method for planar microwave
devices was developed. Various microstrip circuits on substrates with different
thickness and dielectric constants have been analyzed in order to test the method. The
method was validated by a very good matching between simulated data and
measurements, literature data or, for simple cases, comparisons with commercial
software. Coupling between rings have been realized by using capacitive gaps. The
lines between rings and coupling elements provide appropriate transformations from
the gaps or in/out structures as well as a spatial separation between rings. In addition,
the filter response is very sensitive to the input and output couplings. The final
rejection of the four-pole filter could not be measured accurately due to the limitation
in the network analyser dynamic range.
2.0 HTS THIN FILM FABRICATION
Thin Flim HTS prepared off-axis thin films by using single target RF
magnetron sputtering. The superconducting. YBa2Cu3O7-δ thin films were deposited
on Lanthanum Aluminate (LaAlO3) and on Yttria Stabilized Zirconia (YSZ)
substrates. Both “in situ” and “ex situ” methods have been used. “In situ” method was
used for deposition on both sides of the substrates. Standard ceramic technique was
used to produce the target. The raw materials were ground and calcined at 900°C for
12 h. Sintering was carried out in oxygen at 930°C for 20h. The target size was 50 mm
in diameter and 4 mm thick. When the “in situ” method was used, the substrates were
glued on a heated stainless steel piece by using silver paste The actual substrate
temperature was measured using a Chromel-Alumel thermocouple. The substrate was
heated during the deposition. The sputtering gas was a mixture of 50%Ar and 50%O2
at 20 Pa sputtering pressure. The sputtering power was 40 W and the deposition rate
was 100 nm/h. The typical film thickness was in the range of 250-300 nm. oxygen
atmosphere. When the temperature was decreased to 450°C, the oxygen pressure was
increased to 104Pa. The films were additionally kept for 1h at 450°C. Finally the films
were cooled at a rate of 100°C/h down to room temperature. When using the ex-situ
method, the deposition was carried out at room temperature and followed by post
annealing. The post annealing was achieved in a gas flow consisting of a mixture of
N2 and 29 Pa O2 for 3.5 h at 750oC. Next, the films were cooled from 750°C to
450°C at a rate of 3°C/min, in pure oxygen atmosphere at a pressure increasing from
29 Pa to 104 Pa at a rate of 100 Pa/min. The films were further kept at 450°C for 1h in
order to provide them with the necessary amount of oxygen required by stoichiometry.
The films were next cooled at a rate of 100C°/h back to room temperature.
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3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Figure1. Microstrip ring and linear resonators patterned of YBa2Cu3O7-δ thin
film deposited on Yttria Stabilized Zirconia.
An interesting feature of the resonance curves where there are 330 MHz / div, is the presence
of second resonance peak at about 70 MHz below than the main peak. The symmetric
coupling cannot generate this peak-splitting. The second resonance peak can be caused by the
anisotropic nature of the single crystal substrate. The anisotropy can cause a sort of dual
mode effect similar to the dual mode effects observed on loop resonators when non-
symmetrically coupled
3.0 DEVELOPMENT OF GSM 900 RECEIVERS
The research goal was to obtain a good SNR, therefore the RF receiver electronics
was positioned right on the back of the microstrip antenna patches. For each antenna element
in the array, there were two feed points implementing polarization diversity. The second feed
point was also used for calibration. In addition, the IF and RF sections were enclosed in
separate metallic boxes for adequate electromagnetic interference (EMI) isolation.
Figure2. Connection of the sixteen receivers
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4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Signals from RF and IF local oscillators (LOs) were supplied to all the receivers. The power
divider networks for local oscillators signals can be noticed on the back of the antenna. The
receivers’ outputs were provided by 50 coaxial cables to analog to digital converters,
physically situated together with the digital signal processing (DSP) circuitry. To avoid any
spurious noise coupling the DC power was supplied separately for each receiver. The gain of
each receiver was controlled using the voltage gain control (VGC). The signals coming from
the two antenna feed points (RF INPUT 1 and RF INPUT 2) were fed into the RF inputs
LNA IN0 and LNA IN1 of the TQ9203 down-converter. However, the noise reduction
research goal required the isolation of the receiver band from the out-of-band interferences,
especially from the transmission (downlink) signals, which could saturate the LNAs. This
preliminary band selection was performed by preselect SAW filters. The characteristics of the
uplink RF SAW filter used for the array receivers, together with the downlink SAW filter
used for a mobile station (MS) receiver
4.0 DESIGN OF GSM 900 / DCS 1800 TRANSMITTER
A RF transmitter was developed to test the electronics for GSM / GPRS Smart
Antenna. The transmitter was aimed to function for both frequency bands GSM 900 and DCS
1800. For testing, no high output power was demanded. Two versions of the transmitter were
investigated. The first version was developed on the basis of RF2422 2.5 GHz Direct
Quadrature Modulator.
Figure 3. Block schematics of the first version of the GSM 900 / DCS 1800
Transmitter
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5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
5.0 TESTING AND VALIDATION
The RF electronics developed for GSM / GPRS Smart Antenna was tested using HP
8922S “GSM MS Service Test Set” and a normal GSM mobile telephone. Since the test set
provided no auxiliary input, which could be used for DCS 1800, a measurement setup shown
in Fig. 6.23, using a MACOM FR11-0003 circulator (1805-1890 MHz ), and dielectric filters
LARK ENG SSD1747 (1747 MHz) and SSD1842 (1842 MHz) was prepared. The Bit Error
Rate (BER) was found in the limits of the GSM specifications. The RF electronics for GSM /
GPRS Smart Antenna was developed to provide adequate signals for further digital
processing. The spatial filtering was processed in the baseband. The array main beam was
first steered towards the desired mobile phone. The horizontal linear array played an
important role in beamforming in the azimuth plane differentiating easily the users
transmitting from different locations of the cell. In addition, beamforming in the elevation
plane was required especially by the multipath propagation in crowded urban environment.
Following the spatial filtering, the digital signal was filtered in time using the constant
modulus algorithm (CM).
Figure4. Antenna pattern with the main beam steered toward the user's DOA
Figure5. Normalized CIR for punctual sources (dotted line) and sources with
angular spread of 11o
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6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Figure6. The radiation pattern versus angle (degrees) of the microstrip
antenna on 6 dielectric constant substrate at the frequency 7.5 GHz.
6.0 CONCLUSION
The layout effect on some parameters was also taken into account. It was
experimentally proven, that some parameters of the RF down converters, such as the off-
isolation or the LO buffer tuning frequency, were very sensitive to the layout. Furthermore,
an appropriate out-of-band isolation of the IF SAW filters could be obtained only if suitable
design techniques were applied to eliminate the spurious cross couplings between filter ports.
Low noise receivers for GSM 900 uplink, GSM 900 downlink and for DCS 1800 frequency
bands were achieved. A transmitter for both frequency bands was developed in order to test
the system parameters. Sixteen uplink GSM receivers, developed on noise minimization
basis, provided gain uniformity and adequate output signals in order to allow digital
processing of the baseband signals, required by the spatial and time filtering. In spite of the
later rapid evolution of the technological research for HTS thin film deposition, the
developed HTS microstrip resonators constitute an important step towards the realization of
multi-pole, low-loss selective filters. This makes HTS technology very attractive for an
increasingly crowded radio frequency spectrum. The design and fabrication preamble of a
microstrip HTS antenna
is presented. A slot coupled feeding was chosen as a promising configuration for microstrip
antenna arrays. Preliminary measurements on disk slot coupled antennas designed on
different substrates and for different frequencies are presented. HTS antennas were
manufactured on YBCO thin films and the antenna design is presented.
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7. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 2, March – April (2013), © IAEME
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