Aanandan,C K; Mohanan,P; K G Nair(Department of Electronics, August 13, 1984)
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Abstract:
Design and development of a circularly polarized and matched H-plane sectorial horn antenna have been reported By
proper trimming of the flange parameters any desired polarization can be obtained from the horn
Aanandan,C K; K G Nair; Mohanan,P(Department of Electronics, October , 1990)
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Abstract:
A microstrip antenna with large bandwidth is developed
using a parasitic technique. Compared to the available wide-band antenaas,
the proposed antenna structure Is very compact and gives a less
distorted radiation pattern with frequency . An impedance bandwidth,
eight times that of a conventional patch antenna of the same size, Is
achieved. The concept of coupled microstrip line model is extended for
theoretical interpretation of the impedance loci
Aanandan,C K; Mohanan,P; K G Nair(Department of Electronics, October , 1992)
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Abstract:
Reduction of radar cross -section of dihedral corner reflectors using
simulated corrugated surface (SCS) is reported. The technique is
found to be more effective in the reduction of RCS or corner reflectors
for normal incidence . A typical reduction of 40-50 dB is
achieved using this method.
Aanandan,C K; Mohanan,P; Supriyo,Dey; K G Nair(Department of Electronics, 1994)
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Abstract:
A simple technique to improve the impedance bandwidth of a circular
microstrip patch antenna using two sectorial slots is proposed. Using this
design more than 5% impedance bandwidth is obtained. The added
advantage of this new antenna is that it can be fed by a 50 microstrip
line.
Aanandan,C K; Mohanan,P; K G Nair; Supriyo,Dey(Department of Electronics, February 3, 1994)
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Abstract:
The closed form expression for the radiated power of a half-wave
microstrip patch is modified to calculate the impedance
bandwidth of a printed dipole. Analyses of cavity backed flared
and end-loaded printed dipoles are presented
Aanandan,C K; Mohanan,P; K G Nair; Deepukumar,M; George,J(Department of Electronics, August 15, 1996)
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Abstract:
A new dual port microstrip antenna geometry for dual frequency
operation is presented. The structure consists of the intersection
of two circles of the same radius with their centres displaced by a
small fraction of the wavelength . This antenna provides wide
impedance bandwidth and excellent isolation between its ports.
The gain of the antenna is comparable to that of a standard
circular microstrip antenna operating at the same resonant
frequency. A theoretical analysis for calculating the resonant
frequencies of the two ports is also presented
Aanandan,C K; K G Nair; Mohanan,P; Jacob,George(Department of Electronics, November , 1998)
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Abstract:
A new compact microstrip antenna element is analyzed.
The analysis can accurately predict the resonant frequency,
input impedance, and radiation patterns. The predicted results
are compared with experimental results and excellent agreement
is observed . These antenna elements are more suitable in applications
where limited antenna real estate is available
Aanandan,C K; Mohanan,P; Vasudevan,K; Shynu,S V; Gijo,Augustin(Department of Electronics, 2004)
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Abstract:
A novel design of a computer electronically reconfigurable dual frequency dual polarized single feed hexagonal slot loaded microstrip antenna in L-band is introduced in this chapter. pin diodes are used to switch the operating frequencies considerably without much affecting the radiation characteristics and gain. the antenna can work with a frequency ratio varying in the wide range from 1.2 to 1.4. the proposed design has an added advantage of size reduction up to 72.21% and 46.84% for the two resonating frequencies compared to standard rectangular patches. the design also gives considerable bandwidth of up to 2.82% and 2.42 % for the operating frequencies.
Bindu, G; Santhosh John, Abraham; Anil, Lonappan; Vinu, Thomas; Anandan, C K; Mathew, K T(International Journal of Cancer Research, 2006)
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Abstract:
Despite its recognized value in detecting and characterizing breast disease, X-ray
mammography has important limitations that motivate the quest for alternatives to augment
the diagnostic tools that are currently available to the radiologist. The rationale for pursuing
electromagnetic methods are based on the significant dielectric contrast between normal
and cancerous breast tissues, when exposed to microwaves. The present study analyzes
two-dimensional microwave tomographic imaging on normal and malignant breast tissue
samples extracted by mastectomy, to assess the suitability of the technique for early
detection ofbreast cancer. The tissue samples are immersed in matching coupling medium
and are illuminated by 3 GHz signal. 2-D tomographic images ofthe breast tissue samples
are reconstructed from the collected scattered data using distorted Born iterative method.
Variations of dielectric permittivity in breast samples are distinguishable from the obtained
permittivity profiles, which is a clear indication of the presence of malignancy. Hence
microwave tomographic imaging is proposed as an alternate imaging modality for early
detection ofbreast cancer.
Bindu, G; Anil, Lonappan; Vinu, Thomas; Anandan, C K; Mathew, K T(Progress In Electromagnetics Research, 2006)
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Abstract:
Permittivity and conductivity studies of corn syrup in
various concentrations are performed using coaxial cavity perturbation
technique over a frequency range of 250 MHz–3000 MHz. The results
are utilized to estimate relaxation time and dipole moments of the
samples. The stability of the material over the variations of time is
studied. The measured specific absorption rate of the material complies
with the microwave power absorption rate of biological tissues. This
suggests the feasibility of using corn syrup as a suitable, cost effective
coupling medium for microwave breast imaging. The material can also
be used as an efficient breast phantom in microwave breast imaging
studies.
Bindu, G; Anil, Lonappan; Vinu, Thomas; Anandan, C K; Mathew, K T(Progress In Electromagnetics Research, 2006)
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Abstract:
Active microwave imaging is explored as an imaging
modality for early detection of breast cancer. When exposed to
microwaves, breast tumor exhibits electrical properties that are
significantly different from that of healthy breast tissues. The
two approaches of active microwave imaging — confocal microwave
technique with measured reflected signals and microwave tomographic
imaging with measured scattered signals are addressed here. Normal
and malignant breast tissue samples of same person are subjected to
study within 30 minutes of mastectomy. Corn syrup is used as coupling
medium, as its dielectric parameters show good match with that of
the normal breast tissue samples. As bandwidth of the transmitter is
an important aspect in the time domain confocal microwave imaging
approach, wideband bowtie antenna having 2:1 VSWR bandwidth
of 46% is designed for the transmission and reception of microwave
signals. Same antenna is used for microwave tomographic imaging too
at the frequency of 3000 MHz. Experimentally obtained time domain
results are substantiated by finite difference time domain (FDTD)
analysis. 2-D tomographic images are reconstructed with the collected
scattered data using distorted Born iterative method. Variations of
dielectric permittivity in breast samples are distinguishable from the
obtained permittivity profiles.
Shynu, S V; Gijo, Augustin; Anandan, C K; Mohanan, P; Vasudevan, K(Progress In Electromagnetics Research, 2006)
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Abstract:
The design of a compact, single feed, dual frequency
dual polarized and electronically reconfigurable microstrip antenna is
presented in this paper. A square patch loaded with a hexagonal slot
having extended slot arms constitutes the fundamental structure of
the antenna. The tuning of the two resonant frequencies is realized by
varying the effective electrical length of the slot arms by embedding
varactor diodes across the slots. A high tuning range of 34.43%
(1.037–1.394 GHz) and 9.27% (1.359–1.485 GHz) is achieved for the
two operating frequencies respectively, when the bias voltage is varied
from 0 to −30 V. The salient feature of this design is that it uses no
matching networks even though the resonant frequencies are tuned in
a wide range with good matching below −10 dB. The antenna has an
added advantage of size reduction up to 80.11% and 65.69% for the two
operating frequencies compared to conventional rectangular patches.
Bindu, G; Vinu, Thomas; Anil, Lonappan; Anandan, C K; Mathew, K T(John Wiley & Sons, January , 2006)
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Abstract:
A phantom that exhibits complex dielectric properties similar to low-water-content biological tissues over the electromagnetic spectrum of 2000–3000 MHz has been synthesized from carbon black, graphite powder, and poly vinyl acetate (PVA)-based adhesive. The material overcomes various problems that are inherent in conventional phantoms such as decomposition and deterioration due to the invasion of bacteria or mold. The absorption coefficients of the material for various concentrations of carbon and graphite are studied. A combination of 50% poly-vinyl-acetate-based adhesive, 20% carbon, and 30% graphite exhibits a high absorption coefficient, which suggests another application of the material as a good microwave absorber for the interior lining of tomographic chamber in microwave imaging. The cavity-perturbation technique is adopted to study the dielectric properties of the material.
Deepti Das, Krishna; Aanandan, C K; Mohanan, P; Vasudevan, K(John Wiley & Sons, March 3, 2006)
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Abstract:
Design of a dual-port circular patch antenna with a sector-slot for dual-frequency operation is presented. The antenna resonates at two distinct frequencies with orthogonal polarizations and broad radiation characteristics. Unlike the conventional circular patch, this antenna can be microstrip-fed to operate at either of the resonances. The two polarizations can be simultaneously excited using two electromagnetically coupled ports with an isolation better than −30 dB between the ports. This antenna has the added advantage of size reduction of 44% compared to the conventional circular patch without any reduction in gain.
Shynu, S V; Augustin, G; Aanandan, C K; Mohanan, P; Vasudevan, K(IET, March 16, 2006)
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Abstract:
A new electronically reconfigurable dual frequency microstrip patch antenna with highly simplified varactor tuning circuitry is presented. The proposed design allows relatively independent selection of the two operating frequencies. Tuning ranges of 7.1 and 4.1% are realised for the two resonant frequencies without the use of any matching circuits.
Gijo, Augustin; Shynu, S V; Mohanan, P; Anandan, C K; Vasudevan, K(Electronics Letters, April 27, 2006)
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Abstract:
A compact dual-band printed antenna covering the 2.4 GHz (2400-2485 MHz) and 5.2 GHz (5150-5350 MHz) WLAN bands is presented. The experimental analysis shows a 2:1 VSWR bandwidth of up to 32 and 8% for 2.4 and 5.2 GHz, respectively. The measured radiation patterns are nearly omnidirectional, with moderate gain in both the WLAN bands.
Jitha, B; Nimisha, C S; Anandan, C K; Mohanan, P; Vasudevan, K(John Wiley & Sons, July , 2006)
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Abstract:
The use of a split-ring resonator (SRR)-loaded waveguide for the design of a band-rejection filter with adjustable bandwidth is reported. The width of the stopband can be adjusted by suitably positioning the SRR array in the waveguide. The rejection band can be made very narrow by placing the array at the electric-field minimum. The stopband attenuation depends on the number of unit cells in the array.
Deepti Das, Krishna; Gopikrishna, M; Anandan, C K; Mohanan, P; Vasudevan, K(Electronics Letters, August 3, 2006)
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Abstract:
Design of a dual linearly-polarised microstrip patch antenna, excited
by two orthogonal microstrip feed lines, is presented. A reduction in
patch size of 35% is obtained when compared to a square patch
operating at the same frequency. The polarisations are oriented at +45
and - 45 with an isolation of more than 36 dB between the ports.
Unlike earlier designs, the proposed structure provides better gain.