Nagendra P. Pathak

A Fusion Approach to Retrieve Soil Moisture With SAR and Optical Data

The retrieval of soil moisture in vegetated areas with active microwave remote sensing is a challenging process because scattering form the vegetated area incorporates the volume scattering from the vegetation cover and surface scattering from the underlying soil. In addition to this, vegetation provides two way attenuation for the signal scattering from the underlying soil. Therefore, retrieval of soil moisture requires such an approach that may adequately represent the scattering behavior from the vegetation covered area by defining the scattering term from the vegetation and vegetation covered soil clearly. Characterization of scattering due to vegetation is another cumbersome and complex process because it needs several vegetation parameters as input and important problem is that these vegetation parameters exhibit temporal behavior. Therefore, it is the need of present scenario to look for such an alternate approach that may not require the scattering characterization of the concerned vegetation moreover employs the ancillary information. Normalized difference vegetation index (NDVI) which can be obtained with optical data and is an indicator of vegetation, may be efficiently employed with SAR for retrieval of soil moisture in the vegetated area. With this aspect, present paper aims to fuse the information from PALSAR (Phased Array type L-band Synthetic Aperture Radar) and MODIS (Moderate Resolution Imaging Spectroradiometer) data to develop an algorithm for soil moisture retrieval in vegetation covered area. A knowledge based approach involving various polarizations (linear, circular, linear 45, co- and cross-polarized ratios for both linear and circular polarization) is used for land cover classification by which urban and water area can be masked. A normalized scattering based empirical model is developed where normalized coefficient is a function of vegetation characteristic (i.e., NDVI). The developed relationship provides the scattering coefficient of bare soil in HH- and VV-polarization and these values were subsequently used in Dubois Model, which has been solved with copolarization ratio approach to provide volumetric soil moisture content irrespective of roughness value. Two sets of images were used to test and validate the developed algorithm. The obtained results are in good agreement with the ground truth values and have potential to apply for soil moisture retrieval in large scale.

Concurrent dual-band RF system for human respiration rate and heartbeat detection

This article illustrates application of a concurrent dual-band RF system for human respiration and heartbeat detection. The system simultaneously operates at 2.4-/5.2-GHz band. Overall performance of the system is studied in ADS (Advanced Design System) simulation platform, wherein measured S-parameters of dual-band subsystems are utilized. In the experimental setup, signals are measured with a human subject at a distance of 1m away from the RF transceiver. Signals are correlated to mitigate effects of environmental and system noise. Detected signals confirm advantages of the proposed concurrent dual-band system. Measurements exhibit high accuracy for heartbeat and respiration rate detection.

Dual-Input Dual-Output RF Sensor for Indoor Human Occupancy and Position Monitoring

This paper reports a concurrent dualband occupancy sensor, based on Doppler principle, for monitoring of human presence in a room. The proposed sensor operates simultaneously at 2.44 and 5.25-GHz frequency bands. The sensor prototype has been realized using own customized concurrent dualband subsystems. A measurement setup has been developed using off-the-shelf laboratory equipment and the sensor prototype. The human presence in a room has been predicted from the analysis of correlation spectrum of the signals received at individual frequency bands and from the estimation of the direction of arrival of received signals. The main advantage of the proposed sensor lies in the reduction of the false alarms, power consumption, and size.

THE EFFECT OF SOIL TEXTURE IN SOIL MOISTURE RETRIEVAL FOR SPECULAR SCATTERING AT C- BAND

The objective of this paper is to analyze the behavior of specular scattering for difierent soil texture flelds at various soil moisture (mv) and analyze the data to retrieve the soil moisture with minimizing the efiect of the soil texture. To study the soil texture efiect on specular scattering 10 difierent soil flelds were prepared on the basis of change in soil constituents (i.e., percentage of sand, silt and clay) and experiments were performed in both like polarizations (i.e., HH-polarization and V V -polarization) at various incidence angles (i.e., varying incidence angle from 25 - to 70 - in step of 5 - ). Angular response of specular scattering coe-cients (ae - in HH-polarization and ae - vv in V V -polarization) were analyzed for difierent soil texture flelds with varying soil moisture content whereas the surface roughness condition for all the observations were kept constant. The changes in specular scattering coe-cient values were observed with the change in soil texture flelds with moisture for both like polarizations. Further, copolarization ratio (P = ae - /ae -) study was performed and it was observed that the dependency of copolarization ratio for change in soil texture fleld at constant soil moisture is less prominent whereas the value of copolarization ratio is varying with variation of moisture content. This emphasizes that copolarization ratio may be minimizing the efiect of soil texture while observing the soil moisture on specular direction. Regression analysis is carried out to select the best suitable incidence angle for observing the moisture and texture at C-band in specular direction and 60 - incidence angle was found the best suitable incidence angle. An empirical relationship between P and mv was developed for the retrieval of mv and the obtained relationship gives a good agreement with observed mv. In addition, mv was also retrieved

Sensors Augmentation Influence Over Trust and Reputation Models Realization for Dense Wireless Sensor Networks

This paper reports the power consumption and resource utilization of a trust and reputation model deployed in a wireless sensor network (WSN). The impact of sensor augmentation parameter for static and dynamic WSN with trust and reputation models has been examined. In particular, we present a novel WSN framework-based investigations on peer trust and linguistic fuzzy trust model (LFTM) for trust and reputation models. Accuracy, path length, and energy consumption of sensor node operations are reported for their current and average scenarios. In addition, we emphasized over the satisfaction evaluation for LFTM model in the deployed WSN framework. The performance of the sensor augmentation for our proposed framework is evaluated via analytic bounds and numerical simulations. Analytical results together with simulation results exhibit the eminence of the proposed sensor augmentation-based realization over past trust and reputation model investigations.

Comprehensive event based estimation of sensor node distribution strategies using classical flooding routing protocol in wireless sensor networks

We derive a new investigation for the wireless sensor networks (WSNs) when the underlying sensor node distribution strategies have strong influence on event specific communication performance. In this paper, we inclusively evaluated eight sensor network distributions namely: normal, gamma, exponential, beta, generalized inverse Gaussian, poison, Cauchy and Weibull. We designed and illustrated our proposed model with these node distributions for data dissemination. Moreover, performance evaluation matrices like sense count, receive count and receive redundant count are also evaluated. Additionally, we emphasized over the routing protocol behavior for different distribution strategies in the deployed WSN framework. Finally, simulation analysis has been carried out to prove the validity of our proposal. However, routing protocol for WSNs seems intractable to the sensor node distribution strategies when varied from one to another in the scenario.

Concurrent Dual Band Filters Using Plasmonic Slot Waveguide

This letter analyzes the transmission line characteristics of nanoplasmonic metal-insulator-metal waveguide (MIM), a stepped width resonator (SWR), and a band stop filter using SWR. Transmission line characteristics of MIM slot waveguide, such as characteristics impedance and normalized propagation constant, are obtained through full wave simulation. SWR characteristics show two pass bands, hence it is useful in the design of dual band circuits. Subsequently, a band stop filter structure is numerically analyzed. The designed filter has capability of rejecting signals at two wavelengths simultaneously; hence, it is more useful in the development of multiband high-density photonic integrated circuits.

Ferroelectric and Magnetic Properties of Hot-Pressed BiFeO3-PVDF Composite Films

The ferroelectric and magnetic properties of hot-pressed BiFeO3- (BFO) polyvinylidene fluoride (PVDF) composite films have been studied. The BiFeO3 (BFO) ceramics have been synthesized by a rapid liquid phase sintering technique. The X-ray diffraction (XRD) studies revealed that the impure phase observed in pure BFO ceramics was significantly reduced in the composite films. The presence of both ferroelectric and magnetic hysteresis loops confirms the multiferroic nature of the composite films at room temperature. A well-saturated ferroelectric hysteresis loop with a remanent polarization (𝑃𝑟)∼4.8 μC-cm−2 and coercive field (𝐸𝑐)∼1.55 kV/cm has been observed in composite thin films at room temperature. The magnetic hysteresis loops were traced at room temperature with SQUID. The remanent magnetization (𝑀𝑟)∼3.0×10−3 emu/gm and coercive field (𝐻𝑐)∼0.99 kOe was observed in the composite film. The magnetic polarization of the composite films has found to be enhanced as compared to pure BFO and correlated to reduction in BFO impure peak intensity.

Series switched resonator based dual-band oscillator

A series switched resonator based dual-band oscillator, employing single transistor, is reported. The oscillator employs a semiconductor diode, as switch, to change the resonators effective length, thereby, controlling the oscillators negative resistance to shift its output between two desired frequencies. Agilents Advanced Design System (ADS) in conjunction with the electromagnetic simulation tool (EMDS) were used to design the oscillator. The measured characteristics of the fabricated dual-band oscillator, operating near 5.7 GHz and 6.48 GHz, indicate constant output power levels of 4.02 dBm with second harmonic power levels being at least 12 dB below. The measured characteristics also indicate −116.3 dBc/Hz and −95.23 dBc/Hz phase noise levels at 1 MHz offset for the above mentioned two cases, respectively.

Impact of malicious servers over trust and reputation models in wireless sensor networks

This article deals with the impact of malicious servers over different trust and reputation models in wireless sensor networks. First, we analysed the five trust and reputation models, namely BTRM-WSN, Eigen trust, peer trust, power trust, linguistic fuzzy trust model. Further, we proposed wireless sensor network design for optimisation of these models. Finally, influence of malicious servers on the behaviour of above mentioned trust and reputation models is discussed. Statistical analysis has been carried out to prove the validity of our proposal.