Flexible and miniaturized design of microstrip patch antenna with improved cross-polarized radiation

A simple and miniaturized design of rectangular microstrip patch antenna (RMPA) is presented with improved cross-polarization (XP) purity. This design approach is much more flexible to tune the resonance frequency of the antenna for its optimum performance. A complete design guideline based on theoretical analysis has been provided to estimate the antenna resonance frequency and corresponding resonant mode. The higher-order spurious mode, orthogonal to the co-polarized fields, has been identified as the source of XP radiation. The physical insight into the XP suppression has been thoroughly discussed and successfully applied for an optimum design. An improved antenna configuration has been realized without any perturbation in the radiating patch or the ground plane. Size, gain, and impedance matching of the proposed antenna have also been considered along with the suppression of XP value. This may be applicable to any conventional working RMPA by introducing very small possible changes. As much as 16 dB suppression of XP radiation is realized in the H-plane without affecting the co-polarized peak-gain value of 5.27 dBi. The proposed concept has been experimentally validated using a set of antenna prototypes. Measured results are closely corroborated with the simulated predictions. (C) 2020 Elsevier GmbH. All rights reserved

Energy Aware Channel Allocation with Spectrum Sensing in Pilot Contamination Analysis for Cognitive Radio Networks

Cognitive radio (CR) is an innovative and contemporary technology that has been making an effort to overcome the problems of bandwidth reduction by rising the usage of mobile cellular bandwidth connections. The reallocation and distribution of channels is a fundamental characteristic of cellular mobile networks (CMN) to exploit the consumption of CMS. Meanwhile, throughput maximization might lead to higher power utilization, the spectrum sensing system must tackle the energy throughput tradeoff. The spectrum sensing time should be defined by the residual battery energy of secondary user (SU). In that context, energy effective algorithm for spectrum sensing should be developed for meeting the energy constraint of CRN. This study designs a new quantum particle swarm optimization-based energy aware spectrum sensing scheme (QPSO-EASSS) for CRNs. Here, the presented QPSO-EASSS technique dynamically estimates the sensing time depending upon the battery energy level of SUs and the transmission power can be computed based on the battery energy level and PU signal of the SUs. In addition, in this work, the QPSO-EASSS technique applies the QPSO algorithm for throughput maximization with energy constraints in the CRN. The detailed set of experimentations take place and reported the improvements of the QPSO-EASSS technique compared to existing models

Seroprevalencija leptospiroze među zatočenim azijskim slonovima u Kerali, Indija - kratko priopćenje

Leptospirosis is an infectious disease of zoonotic significance, caused by distinct members of the genus Leptospira, with a broad spectrum of hosts, including domestic and wild animals. The present paper reports the seroprevalence of leptospirosis among captive Asian elephants in Kerala. Whole blood samples were collected from fifty, apparently healthy captive elephants from different districts of Kerala state. The serum was separated from the whole blood and subjected to the Microscopic Agglutination Test (MAT) for detection of antibodies to different serovars of Leptospira. The test was carried out using actively grown cultures of twelve common leptospiral serovars. Out of the total of fifty serum samples screened by MAT, 19 samples (38 per cent) showed a positive reaction with antibody titres in a 1:200 dilution. The prevalent serovars were Pomona, Icterohaemorrhagiae, Hebdomadis, Grippotyphosa and Canicola, and the highest prevalence was noticed for the serovar Pomona. The positive results indicated the presence of infection or the previous exposure of captive elephants to leptospiral antigens. The high rate of prevalence of leptospiral antibodies in captive elephants warrants the monitoring of these animals for clinical disease and adopting the necessary control strategies for preventing this re-emerging zoonotic disease.Leptospiroza je zarazna bolest od zoonotske važnosti uzrokovana različitim pripadnicima roda Leptospira, koja ima velik raspon domaćina, uključujući domaće i divlje životinje. U ovom je radu prikazana seroprevalencija leptospiroze među zatočenim azisjkim slonovima u Kerali u Indiji. Uzorci pune krvi prikupljeni su od naizgled zdravih pedeset zatočenih slonova iz različitih okruga Kerale. Serum je odvojen od pune krvi i podvrgnut mikroskopskom testu aglutinacije (MAT) radi otkrivanja protutijela na različite serovarove leptospira. Test je proveden uz upotrebu aktivno uzgojenih 12 učestalijih serovarova leptospira. Od ukupno pedeset uzoraka seruma analiziranih MAT-om 19 uzoraka (38 %) pokazalo je pozitivnu reakciju s titrom protutijela pri razrjeđenju 1:200. Najučestaliji su serovarovi bili Pomona, Icerohaemorrhagiae, Hebdomadis, Grippotyphosa i Canicola, s najvećom uočenom prevalencijom za serovar Pomona. Pozitivni rezultati upućuju na prisutnost infekcije ili prethodnu izloženost zatočenih slonova antigenima leptospira. Veća stopa prevalencije na protutijela leptospira u zatočenih slonova upozorava na potrebu za praćenjem ovih životinja s obzirom na kliničku bolest te usvajanje potrebnih strategija kontrole radi prevencije ove reemergentne zoonoze

A simplified ion-aerosol model for balloon measurements of ion conductivity and aerosol concentration

A simplified ion-aerosol model scheme is used to predict the small ion depletion and the consequent changes in stratospheric conductivity for the conditions at Hyderabad (17.5-degrees-N, 78.6-degrees-E). The inputs to the model on ion production rate, ion-ion recombination coefficient and charged ion-aerosol recombination coefficient are obtained from parametrization formulae. The balloon experimental results on small ion conductivity and aerosol concentrations at Hyderabad are compared with the simplified model results

Height Variation of Electron Loss Coefficient in the Mesosphere

1-5Electron loss at mesospheric heights is characterized by the parameter Ψ, the effective electron loss coefficient. The value of Ψ is known to be drastically reduced for the disturbed D-region and is more than two orders of magnitude larger than the normal day values for eclipse and nighttime conditions. A log-log plot of Ψ against height, h, gives a linear relation of the form h = KΨ-n; here, the constants K and n are different for different D-region conditions. An attempt is made to find a relation between n and the D-region disturbance

An analytical approach of designing compact microstrip patch antenna using metal-ring superstrate for wideband and broadside radiations

A compact design of microstrip patch antenna is presented to realize wideband characteristics. An annular metal-ring has been used as a superstrate as well as an inductive load to the rectangular patch. Robust analytical technique is applied to choose the dimensions of the ring and the patch where they resonate very close to each other. This strategic approach ensures a wide matching bandwidth with a broadside radiation pattern. An additional enhancement of bandwidth has been achieved by employing a unique design strategy. A set of antenna prototype has been fabricated for experimental validation. As much as 34% matching bandwidth has been revealed experimentally using a compact antenna (similar to lambda x lambda). The boresight gain is maintained about 10 dBi over the operating frequency band. The cross-polarized isolation in E- and H-planes are maintained above 40 dB and 30 dB respectively over the operating bandwidth. The back-radiation of the antenna is also maintained below -20 dB over the wide matching bandwidth

Equatorial water-vapor mixing-ratio from rocket data on positive-ion composition

147-153Available mass spectrometer data on positive ion composition and temperature from Ly- absorption experiment for the equatorial station Thumba (8.5°N) are used in a simplified positive ion-chemical model analysis to derive mesospheric water vapour mixing ratio. The results show the desirability of obtaining accurate temperature data along with mass spectrometer ion composition measurements for a satisfactory estimation of water vapour mixing rations which are scarce at mesospheric heights