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This paper proposes a graphene patch antenna for dual-band operation while maintaining a low profile. The antenna consists of the metasurface-based 4 x 4 AMC configuration and the square graphene patch driven through the aperture coupling. The fundamental TM 10 mode of graphene patch excites the first resonance frequency, while the TM 10 and antiphase TM 20 modes of metasurface simultaneously excite the second wide frequency band. The first resonance frequency excited by the graphene patch can be reconfigured by varying the external DC bias voltage on the graphene patch. An equivalent circuit of antenna using lumped elements has also been proposed using a vector fitting algorithm. The proposed antenna with a profile height of 0. 12 λ 0 (where λ 0 is free space wavelength) at a center frequency of 1.14 THz achieves the gain from 7.06 dB to 10.4 dB in the first band and an average gain of 10 dB in the second band. [ABSTRACT FROM AUTHOR]

This paper proposes a frequency reconfigurable dielectric lens antenna (DLA) to compensate high attenuation due to atmospheric losses in the THz region. An aperture coupled graphene plasmonic nanoantenna has been designed and used to feed DLA. Frequency tuning has been introduced by varying the chemical potential of graphene. A lumped elements equivalent circuit for graphene-based feed antenna has also been proposed. The values of the lumped elements are obtained using the vector fitting algorithm. The proposed DLA has high gain, narrow beamwidth, broadside radiation pattern and stable input impedance. Directivity achieved through simulation is up to 7.3 dBi with radiation efficiency of 70 % and 21.2 dBi with radiation efficiency of 65 % for feed antenna and DLA respectively. The performance of DLA has also been studied as the function of feed element, relative permittivity of lens material, radius of lens and off-axis displacement tolerances. [ABSTRACT FROM AUTHOR]

Abstract: This article illustrates application of a concurrent dual-band RF system and Wavelet Transform for contactless detection and analysis of human vital signs (i.e. Heartbeats and Respiration rate) for the first time. The vital signs are captured by a concurrent dual-band measurement setup operating at 2.4/5.2GHz band. An algorithm using Fourier transform and Wavelet transform is used to notice the vital signs from the phase information signal of the concurrent dual-band RF system. The analysis shows that Wavelet transform gives better prediction of vital sign as compared to Fourier transform. The concurrent dual-band operation yields the advantage of measurement of vital sign signals without a change in measurement conditions at both bands. Simulations are carried out using measured dual-band subsystems in ADS platform. In the experimental setup, signals are measured with a human subject at a distance of 1-m away from the RF transceiver. [Copyright &y& Elsevier]

Abstract: Soil texture is an important soil parameter that is useful for meteorology, climatology, hydrology, ecology, etc. Therefore, it is important to classify soil based on soil texture (i.e., sand, silt and clay). A lot of studies with radar remote sensing have been carried out to estimate soil moisture and surface roughness, but less attention has been given to study the effect of individual soil texture on radar scattering, especially in specular direction. The main aim of this paper is to check the behavior of specular scattering with change in soil texture. This effect has also been analyzed in presence of soil moisture and surface roughness. Scattering coefficient has been retrieved for various soil texture fields with indigenously designed X-band bistatic scatterometer for a range of incidence angles (from 30° to 70° in steps of 10°) in both like polarizations, i.e., HH-polarization and VV-polarization. Observations were made at 10GHz frequency. Four different fields were considered on the basis of soil texture variations; especially changes in sand percentage were made. Roughness (smooth soil to 1.4cm rms surface height) and moisture (dry soil to 0.21cm3 cm−3 volumetric soil moisture) conditions of these fields were varied for observations. Strong change in specular scattering coefficient is observed by changing the sand percentage in soil for HH-polarization, while in case of VV-polarization a lesser change is observed. Also a high change in specular scattering coefficient is noticed once moisture is added to the soil. It is difficult to observe the change in specular scattering coefficient with change in soil texture when surface is considered as rough. Therefore, it is important to minimize the roughness effect while observing the texture with specular scattering. For this purpose, polarization study was carried out to see how polarization can be helpful to minimize the roughness effect. The effect of soil texture on copolarization ratio is critically analyzed, and it is observed that for higher incidence angle (⩾50°), the distinction in soil texture fields are clearly observable on the basis of copolarization ratio. This type of study will be helpful in near future to design the bistatic radar system for soil parameter monitoring, especially for cartwheel satellite system. [Copyright &y& Elsevier]

Abstract: This paper presents preliminary work to address scalability concern over AODV protocol in wireless sensor network. Firstly, we discussed the scalability design issues with related work in context of wireless sensor networks (WSN). Following, we designed and illustrated wireless sensor network model. Finally, significance of scalability on the behaviour of application, MAC, transport and physical layer performance is described. [Copyright &y& Elsevier]