Cross‐polarization reduction of microstrip antenna using microwave absorbers

In this article, a metamaterial inspired microwave absorber is used to reduce the cross‐polarization (XP) level of the radiated wave in microstrip antenna (MSA). A microwave absorber unit‐cell has been analyzed and implemented to reduce the cross polarization (XP) level in a single element and a 2 × 2 microstrip patch array antennas. The antennas have been designed on a FR‐4 substrate of thickness 0.8 mm at 10.1 GHz center frequency. The 2 × 2 patch array antenna with and without the absorbers have been experimentally verified for the S11 parameter, the radiation pattern, and the XP suppression in H‐plane and a good comparison has been found.     

Effect of unit-cells of the frequency selective surface as superstrate on the directivity of rectangular microstrip antenna

In this paper, the relationship between the number of unit-cells used in the design of a frequency selective surface (FSS) and its expected directivity is established. The relationship between the number of FSS unit-cells and the directivity is based on the planer microstrip patch array antenna design concept where the unit-cell is treated as the superstrate illuminated by the source. To validate the proposed technique, the analytical value of the directivity has been compared with that of ray-tracing method. The directivity of antenna is calculated for two different planar array configurations at 600 GHz. The results of numerical analysis are compared to that of the full-wave electromagnetic simulator CST Microwave Studio and results are comparable. Further, the directivity computed by this proposed technique has also been compared with that of the reported in literatures.     

A slow wave structure and its application in bandpass filter design

This paper presents a new slow wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of different kind of coupling in this structure is demonstrated. Two and four resonator band pass filters at center frequency 2.15 and 2.30 GHz with different bandwidth are designed. The simulated results are verified with the help of two different software packages (IE3D and Sonnet Lite).     

Development and Characterization of Inorganic-Organic (Si-O-Al) Hybrid Geopolymeric Precursors via Solid State Method

Silicon - In this study, an innovative one part, solution free concept applied for the development of hybrid inorganic–organic geopolymeric precursors having Si-O-Al networks at the precursor...     

Analysis and design of enhanced directivity microstrip antenna at terahertz frequency by using electromagnetic bandgap material

In this paper, an electromagnetic bandgap (EBG) material in the range of 0.5–0.8 THz has been simulated with Arlon AR 600 (ε=6.0) as host material and air‐cylinders as the foreign embedded material. The effective dielectric permittivity of this material has been analyzed at the frequency range of 0.590–0.620 THz. The reduced effective dielectric permittivity substrate of thickness 50 µm has been used to design the microstrip antenna at 600 GHz with a novel approach. This proposed antenna shows an enhanced directivity of 15.1 dBi at 600 GHz frequency. To compare the analysis, the operating frequency has been scaled down by a factor of 100 and various results have been compared by using two different commercially available simulators CST Microwave Studio based on the finite integral technique and Ansoft HFSS based on the finite element method. Copyright © 2010 John Wiley & Sons, Ltd.     

Performance analysis of an open-loop resonator loaded terahertz microstrip antenna

In this paper, an enhanced electrical performance of the open-loop loaded microstrip patch antenna at terahertz frequency has been investigated. The proposed antenna is designed to radiate at frequencies in the range of 0.5-0.7 THz with high gain and radiation efficiency. The effect of various substrate parameters on the electrical performance of the proposed antenna has been analyzed and simulated. The simulation has been performed using the CST Microwave studio, a commercial simulator based on finite integral technique. The directivity and radiation efficiency of the proposed antenna is 22.58 dBi and 94.50%, respectively, at 600 GHz. Further, the simulated results have been compared with Ansoft HFSS, a commercially available simulator based on the finite element method. We have also compared this proposed analytical result with reported literature with scale down approach.     

Analysis of the Effect of Ground Plane Size on the Performance of a Probe-fed Cavity Resonator Microstrip Antenna

In this paper, a probe-fed rectangular microstrip patch antenna with partially reflective superstrate at terahertz frequency (600 GHz) has been analyzed and simulated. The analysis of the partially reflective surface shows the highly reflective property of the surface over the wideband of the frequencies. The analysis of a specific configuration (rectangular patch) of partially reflective surface predicts the directivity of antenna to be the order of 24 dBi and subsequently it has been validated with the simulation. The proposed antenna has been simulated by using commercially available CST Microwave Studio simulator based on finite integral technique. Next to this, the application scenario of this kind of the antenna in the terahertz regime of the electromagnetic spectrum has been discussed and it has been obtained that this antenna is capable to establish 9 m long communication link.     

Correction to: Proposed Model for Radio Wave Attenuation due to Rain (RWAR)

Wireless Personal Communications - A correction to this paper has been published: https://doi.org/10.1007/s11277-021-08370-x     

Improvement of phone recognition accuracy using speech mode classification

In this work, we have developed a speech mode classification model for improving the performance of phone recognition system (PRS). In this paper, we have explored vocal tract system, excitation source and prosodic features for development of speech mode classification (SMC) model. These features are extracted from voiced regions of a speech signal. In this study, conversation, extempore, and read speech are considered as three different modes of speech. The vocal tract component of speech is extracted using Mel-frequency cepstral coefficients (MFCCs). The excitation source features are captured through Mel power differences of spectrum in sub-bands (MPDSS) and residual Mel-frequency cepstral coefficients (RMFCCs) of the speech signal. The prosody information is extracted from pitch and intensity. Speech mode classification models are developed using above described features independently, and in fusion. The experiments carried out on Bengali speech corpus to analyze the accuracy of the speech mode classification model using the artificial neural network (ANN), naive Bayes, support vector machines (SVMs) and k-nearest neighbor (KNN). We proposed four classification models which are combined using maximum voting approach for optimal performance. From the results, it is observed that speech mode classification model developed using the fusion of vocal tract system, excitation source and prosodic features of speech, yields the best performance of 98%. Finally, the proposed speech mode classifier is integrated to the PRS, and the accuracy of phone recognition system is observed to be improved by 11.08%.     

Robust vowel region detection method for multimode speech

Multimedia Tools and Applications - The aim of this paper is to explore a robust method for vowel region detection from multimode speech. In realistic scenario, speech can be classified into three...