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This paper proposes a novel planar metamaterial structure which displays double negative (DNG) properties in popular bands such as S and C. DNG refers to materials which show simultaneously negative permeability and permittivity. The... more
This paper proposes a novel planar metamaterial structure which displays double negative (DNG) properties in popular bands such as S and C. DNG refers to materials which show simultaneously negative permeability and permittivity. The proposed structure is developed through simulation using HFSS and its characterization is done through various methods such as S-parameter retrieval method and cavity perturbation method. The results of simulated and measured S parameters are used for the retrieval of various material properties. Further verification of obtained results is carried out through cavity perturbation, and the observed results using various methods complement each other confirming the DNG behavior of the newly designed material.
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Various signal processing window functions are applied on the back scattered signals received from the lower atmosphere by the ST radar facility at Advanced Center for Atmospheric Radar Research, Cochin. It is observed that the ground... more
Various signal processing window functions are applied on the back scattered signals received from the lower atmosphere by the ST radar facility at Advanced Center for Atmospheric Radar Research, Cochin. It is observed that the ground clutter present in the Doppler spectra of a particular range bin is either enhanced or suppressed with the usage of different windowing functions. Further analysis is carried out to evaluate the Doppler-Clutter Peak Power Difference of different window functions. The analysis show that the clutter suppression capability of a window is closely associated with its 3dB bandwidth. The windows with narrow bandwidth show better clutter suppression capability subjected to its relative side lobe level.
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This paper presents the enhancements obtained in the performance of the Sample Matrix Inversion (SMI) beamformer by the application of Reduced One Dimensional Mapped Real Transform (R-ID-MRT) algorithm. In SMI beamformers, computational... more
This paper presents the enhancements obtained in the performance of the Sample Matrix Inversion (SMI) beamformer by the application of Reduced One Dimensional Mapped Real Transform (R-ID-MRT) algorithm. In SMI beamformers, computational complexity and the time required for computation is reduced when data is transformed with R-ID-MRT algorithm. The beam patterns, convergence to the desired beam output, minimization of mean square error in AWGN, Rayleigh and Rician channels of the R-ID-MRT SMI beamformers are comparable to that of conventional SMI beamformers.
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The paper presents a comparative study of rectangular spiral resonators and their behaviour in a coplanar waveguide and a microstrip transmission line structure. When coupled to a coplanar waveguide line they imitate a series connected... more
The paper presents a comparative study of rectangular spiral resonators and their behaviour in a coplanar waveguide and a microstrip transmission line structure. When coupled to a coplanar waveguide line they imitate a series connected parallel LC resonant circuit to introduce a notch band. When directly connected to a microstrip line they form a shunt connected series LC resonant circuit to produce the required notch band. The third attempt places the spiral resonator inside the microstrip transmission line. Filter structures are developed utilizing these behaviour and their characteristics are compared. Spiral resonators are tuned to the mid band frequency (403.5MHz) of the MICS band (402MHz-405MHz).
In this paper, two antenna geometries for multiband applications are presented. The fundamental structure consists of a circular monopole with a hexagonal slot inscribed. This structure yields different operating bands which are suitable... more
In this paper, two antenna geometries for multiband applications are presented. The fundamental structure consists of a circular monopole with a hexagonal slot inscribed. This structure yields different operating bands which are suitable for global systems for mobile communications (GSM 1800/1900 1.71-1.88 GHz/1.85-1.99 GHz), wireless technology for personal area networks (Bluetooth 2.4-2.485 GHz) and international mobile telecommunications advanced system for fourth generation mobile communication (IMT-advanced 3.4-4.2 GHz). A higher operating band is obtained at upper wireless local area network (WLAN 5.725-5.825 GHz) by two different designs. The two designs are simulated using Ansys HFSS and the radiation characteristics of the two antennas are presented.
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Two novel, compact, U-shaped slot resonator-based 8-bit chipless RFID tags covering wide-band for identification, tracking and sensing applications are presented in this paper. The tags are designed on a flexible DuPont substrate having... more
Two novel, compact, U-shaped slot resonator-based 8-bit chipless RFID tags covering wide-band for identification, tracking and sensing applications are presented in this paper. The tags are designed on a flexible DuPont substrate having relative permittivity 4, loss tangent 0.027 and thickness 50 µm. Both the tags have the same structure, but are arranged differently. In tag-1, 8 U-shaped resonators are arranged in a cascaded fashion, whereas in tag-2, one set formed by alternate 4 slots are arranged in one half of the substrate, while the remaining are arranged in the second half with an inverted configuration. The Radar Cross Section (RCS) responses of the two tags are obtained to demonstrate the 8 unique resonances with adequate separation. A flexibility study has been carried out to validate the distinguishable nature of bits under different bending conditions. An experimental set up with two wide-band antennas are used to measure the S21 of the fabricated tags in the laboratory. Different arrangements of antennas to establish the reflected and transmitted signal performance of the proposed tags are presented in this paper.
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Synthetic aperture radar (SAR) ship classification research mainly focuses on large ships with distinctive features. Also, ship types are expanding nowadays. Traditional standard image classification techniques are not adequate for the... more
Synthetic aperture radar (SAR) ship classification research mainly focuses on large ships with distinctive features. Also, ship types are expanding nowadays. Traditional standard image classification techniques are not adequate for the effective classification of SAR ships due to their fewer available data in some classes (unbalanced data). We are introducing a one-shot learning-based deep learning model built from scratch to classify 16 ship classes to solve these. It generates embeddings of size 20 and uses distance measure for classification. Also, we propose a preprocessing stage (PP-stage) and feature fusion (FF-stage) technique to improve classification accuracy. Experimental results on the OpenSARShip dataset for ship classification reveal that the accuracy is superior to the other state-of-the-art SAR image classifiers.
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In this article, a compact dual band metamaterial inspired circular microstrip patch antenna for WLAN applications is presented. The antenna consists of a circular patch loaded with a complementary double negative metamaterial structure... more
In this article, a compact dual band metamaterial inspired circular microstrip patch antenna for WLAN applications is presented. The antenna consists of a circular patch loaded with a complementary double negative metamaterial structure which produces a percentage miniaturisation of 60.7%. The circular microstrip patch antenna used for developing the proposed antenna has a resonant frequency of 6.2 GHz with an impedance bandwidth of 3.5% before the metamaterial structure is applied upon it. The loading of the proposed metamaterial structure inspires the antenna to lower its resonant frequency with enhanced bandwidth and generate one additional resonance. The designed antenna can be tuned throughout the C-band by simply altering the size of the metamaterial structure loaded upon it. However, the prototype of the antenna is designed for the most commonly used wireless communication bands at 2.4 GHz and 5.2 GHz. The 10 dB impedance bandwidth of 1.63% at 2.4 GHz and 13.15% at 5.2 GHz ar...
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ABSTRACT: A compact multihand planar octagonal-shaped microstrip antenna simultaneously suitable for mobile communication and blue tooth application is presented. The antenna provides sufficient isolation benveen the two operating bands... more
ABSTRACT: A compact multihand planar octagonal-shaped microstrip antenna simultaneously suitable for mobile communication and blue tooth application is presented. The antenna provides sufficient isolation benveen the two operating bands and an area reduction of-29 % with respect to a circular patch operating in the same band. © 2002 Wiley
The paper presents the optimization of the notch band in an Ultra Wide Band (UWB) serrated monopole antenna using a modified Genetic Algorithm approach. The results are compared with that of a similar antenna where the slot is designed... more
The paper presents the optimization of the notch band in an Ultra Wide Band (UWB) serrated monopole antenna using a modified Genetic Algorithm approach. The results are compared with that of a similar antenna where the slot is designed using conventional approach. The algorithm is found to be highly efficient in terms of computation time and slot area. 1.
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A compact asymmetric coplanar strip fed F shaped monopole antenna for dual band applications is presented. The antenna exhibits a dual band from 2.22 GHz to 2.54 GHz and from 4.94 GHz to 5.80 GHz covering the 2.4/5.2 GHz WLAN and... more
A compact asymmetric coplanar strip fed F shaped monopole antenna for dual band applications is presented. The antenna exhibits a dual band from 2.22 GHz to 2.54 GHz and from 4.94 GHz to 5.80 GHz covering the 2.4/5.2 GHz WLAN and HIPERLAN2 bands. The dual band nature of the antenna is due to the various current paths excited in the F shaped structure. The uniplanar antenna structure has a compact dimension of 22 mm x 19 mm when printed on a substrate of dielectric constant 4.4 and height 1.6 mm. The antenna exhibits nearly omni directional radiation characteristics and moderate gain in the entire operating bands. The uniplanar nature, simple feeding technique and compact structure make it easy for modular design. The design is validated with experimental and simulated results.
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Deep learning techniques give good results on target classification of MSTAR dataset. Most of the techniques for SAR target identification use only the magnitude information of the raw SAR data and discard the phase information. Deep... more
Deep learning techniques give good results on target classification of MSTAR dataset. Most of the techniques for SAR target identification use only the magnitude information of the raw SAR data and discard the phase information. Deep convolution neural network has the ability to automatically learn from the complex image generated using both the magnitude and phase information from the radar data. In this paper we are proposing a new method for generating the complex image dataset (SAR-COM) and a deep learning model which automatically classifies targets from MSTAR raw data.
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Research Interests: Physics and Microstrip
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Many research works using deep learning techniques for automatic ship detection from SAR images have good detection accuracy. But the main problem in these methods is false detection, mostly due to speckle presence. Therefore, we propose... more
Many research works using deep learning techniques for automatic ship detection from SAR images have good detection accuracy. But the main problem in these methods is false detection, mostly due to speckle presence. Therefore, we propose a new deep learning model with a novel preprocessing stage to address this problem. We are introducing a deep learning architecture to detect and localize ships in the SAR image. First, generate a three-channel image from gray-scale SAR image. Then, this image is used to train the model to predict the ship’s position in the SAR image. We experimented on the public SAR ship detection dataset (SSDD) and Dataset of Ship Detection for Deep Learning under Complex Backgrounds (SDCD) to validate the proposed method’s feasibility. We used python 3.5 for coding with the Keras framework in the NVIDIA Tesla K80 GPU hardware platform. The experimental results indicated that our proposed method’s ship detection accuracy has increased with reduced false detection...
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The time domain modeling of a coplanar wave guide (CPW) fed band-notched antenna for Ultra Wide band (UWB) applications is presented. The annular ring antenna has a dimension of 36x36 mm 2 when printed on a substrate of dielectric... more
The time domain modeling of a coplanar wave guide (CPW) fed band-notched antenna for Ultra Wide band (UWB) applications is presented. The annular ring antenna has a dimension of 36x36 mm 2 when printed on a substrate of dielectric constant 4.4 and thickness 1.6 mm. The uniplanar nature and compact structure of the antenna make it apt for modular design. The crescent shaped slot provides a notch in the 5.2-5.8 GHz frequency band to avoid interference with Wireless Local Area Network (WLAN). The pulse distortion is insignificant in the operating band and is verified by the measured antenna performance with high signal fidelity and virtually steady group delay.
This paper proposes a new metamaterial inspired electrically small multi-band monopole antenna. The proposed antenna is capable of operating at DCS 1800 in the lower band. At the same time, in the higher band, it covers two wireless local... more
This paper proposes a new metamaterial inspired electrically small multi-band monopole antenna. The proposed antenna is capable of operating at DCS 1800 in the lower band. At the same time, in the higher band, it covers two wireless local area network (WLAN) bands at 2.4 and 5.2 GHz. This paper describes the design and detailed analysis of an electrically small (ka = 0.64 < 1) antenna with a -10dB fractional bandwidth of 2.01%, 1.64% and 2.71% for triple-band operations with centre frequencies 1.80, 2.45 and 5.17 GHz. The compactness is achieved by the application of double negative metamaterial on a monopole antenna operating at 9 GHz. The proposed antenna has an overall compact electrical size 0.14 λ0 × 0.14λ0 × 0.01 λ0 at 1.8 GHz and physical dimensions 24 × 24 × 1.6 mm3 including the ground. In this proposed ESA a second DNG structure is also incorporated to enhance its gain. This enables reliable operations at DCS 1800 and WLAN frequencies 2.4 and 5.2 GHz.
Research Interests: Physics and Metamaterial
This paper presents a compact metamaterial (MTM) inspired coplanar waveguide (CPW) fed multiband monopole antenna operate at Bluetooth, WiMAX, WLAN frequency bands. The overall dimension of the antenna is 21x29x1.6 mm3. The antenna... more
This paper presents a compact metamaterial (MTM) inspired coplanar waveguide (CPW) fed multiband monopole antenna operate at Bluetooth, WiMAX, WLAN frequency bands. The overall dimension of the antenna is 21x29x1.6 mm3. The antenna consists of meta inspired monopole along with metamaterial loading resulting in a compact electrical size of $0.23\lambda_{0}\times 0.17\lambda_{0}\times 0.013\lambda_{0}$, where $\lambda_{0}$ is calculated at first resonating frequency 2.4 GHz. The proposed antenna gives quad band operation with centre frequencies 2.4 GHz, 3.4 GHz, 5.1 GHz and 5.8 GHz with −10dB impedance bandwidths of 9.17%, 11.44%, 3.73% and 4.66% respectively.
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In this paper the Time Domain Analysis (TDA) of planar compact Ultra Wide Band (UWB) antenna is carried out. The operating frequencies of the designed antenna are found to be in the range of 2.27 GHz to 12.39 GHz. The antenna parameters... more
In this paper the Time Domain Analysis (TDA) of planar compact Ultra Wide Band (UWB) antenna is carried out. The operating frequencies of the designed antenna are found to be in the range of 2.27 GHz to 12.39 GHz. The antenna parameters are obtained in frequency domain and the subsequent time domain analysis is performed by using rayleigh pulse excitation. Simulation result shows that the antenna holds the integrity of the signal which is calculated by its fidelity factor.
Recent years have witnessed phenomenal developments worldwide in the field of NLP . But developments in Indian regional languages are very few compared to them. This work is a step towards the construction of a target word sense... more
Recent years have witnessed phenomenal developments worldwide in the field of NLP . But developments in Indian regional languages are very few compared to them. This work is a step towards the construction of a target word sense disambiguation system in Malayalam, which is the regional language of the state of Kerala, India. Word Sense Disambiguation/Determination refers to the task of correctly identifying the sense of an ambiguous word from its context. This is considered an AI-Complete problem in the field of Natural Language Processing . For this purpose, an exclusive corpus of 1,147 contexts of target ambiguous words has been created, which to the best of our knowledge is the first attempt in Malayalam. This work describes how the performance of an unsupervised LDA-based approach towards WSD could be improved using semantic features like synonyms and co-occurrence information.
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The paper proposes an octagon shaped Microstrip Patch Antenna suitable for dual band applications. The striking features of this compact, planar antenna are sufficient isolation between the two operating bands and an area reduction of 29%... more
The paper proposes an octagon shaped Microstrip Patch Antenna suitable for dual band applications. The striking features of this compact, planar antenna are sufficient isolation between the two operating bands and an area reduction of 29% in comparison to a conventional circular patch antenna operating in the same band.
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A coplanar waveguide- (CPW-) fed spiral antenna with dual band application is presented. The antenna is designed to operate over the UWB (3.1–10.6 GHz) band as well as in a lower band suitable for WMTS (1.395–1.4 GHz). Frequency domain... more
A coplanar waveguide- (CPW-) fed spiral antenna with dual band application is presented. The antenna is designed to operate over the UWB (3.1–10.6 GHz) band as well as in a lower band suitable for WMTS (1.395–1.4 GHz). Frequency domain characterization shows that the antenna is well matched with appreciable gain in both bands. Time-domain studies are carried out to check the suitability of the antenna in pulsed communication. A prototype of the antenna is fabricated and measured results show low group delay variation in the UWB. FWHM and ringing of antenna impulse response, fidelity factor, and radiated power spectral density are also presented.
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ABSTRACT This paper discusses the measurement of moisture content present in soil by computing the dielectric constant of soil samples at three frequencies, using microwave free-space transmission technique. This leads to the... more
ABSTRACT This paper discusses the measurement of moisture content present in soil by computing the dielectric constant of soil samples at three frequencies, using microwave free-space transmission technique. This leads to the determination of inherent moisture content in the samples by applying Topp&#39;s Equation. The change in the value of dielectric constant and the subsequent increase in the moisture content for each of the soil samples with added moisture levels at 20%, 23.1% and 28.6% are noted. Dielectric constant of some common materials such as free-space, FR4, acrylic and water are measured to check the efficacy of the proposed method.