Anindya Bose

Generating Chaos in Injection-synchronized Gunn Oscillator: An Experimental Approach

AbstractChaotic dynamics of electronic circuits and systems is attracting the interest of researchers for the last few decades, mainly because of its potential for application in electronic communication systems. Different methods can be proposed to drive a microwave Gunn oscillator into chaotic mode. Among them, an injection-locked Gunn oscillator driven by a weak co-channel signal may be a feasible technique. The present work considers this method through a hardware experiment and finds that under certain conditions of interference strength and detuning, chaotic oscillations of a Gunn oscillator can be observed.Abstract Impedance glottography, or electroglottography, is a noninvasive technique for monitoring the variation of the degree of contact between the vibrating vocal cords during voice production. Electrical impedance is sensed using a pair of electrodes placed on either side of the larynx, by injecting a low-level high-frequency current. A wide-band impedance detector circuit has been developed using a precision rectifier based on voltage feedback clamping amplifier and approximately linear-phase lowpass filter. The circuit can be used for obtaining electroglottogram signal for diagnosis of vocal fold disorders.

The Usefulness of GLONASS for Positioning in the Presence of GPS in the Indian Subcontinent

The effort to integrate the use of GPS and GLONASS constellations resulted in the production of a special receiver, which can use both constellations in combination. These receivers may be used in GPS only mode, GLONASS mode and combined (both GPS and GLONASS) mode. Utilising this type of receiver, GPS and GLONASS signals were monitored for one calendar year simultaneously in different places in India to study the status of visibility of satellites and the positioning accuracy. The number of satellites in GLONASS constellation gradually depleted from 16 to 7 during the course of this study. So a 3-D solution was rarely possible using only GLONASS satellites. However, appreciable improvement in PDOP was observed in the combined mode. Before the withdrawal of GPS Selective Availability (SA), significant improvement of position accuracy could be observed in the combined mode. After the removal of GPS-SA, the accuracies of the combined mode and that of GPS-only mode have been found to be of the same order. While this does not apparently reflect any advantage, it indirectly confirms that both the GPS and the GLONASS systems have similar limits of accuracy and also confirms that optimal interoperability of two systems has been achieved. These studies reveal that the combined use of GLONASS and GPS will always be beneficial to a varying degree depending on different applications and circumstances.

A study on the potentiality of the GPS timing receiver for real time applications

Two categories of GPS timing receivers have been identified for real time applications. Performances of a few such receivers have been studied. The GPS time in some of the receivers has been found to have some bias error. This demands the necessity of the calibration of the GPS receiver prior to its precise application. It has been observed that the time error (or phase error) normally remains constant for a particular receiver. So this may not affect the frequency accuracy.

Rectangular Active Microstrip Patch Antennas Revisited

Based on a simple, but accurate transmission line model a new formula for location the position of a Gunn diode on a rectangular microstrip patch antenna has been proposed. It also takes into account the intrinsic losses of the patch. Unlike the earlier design formula the present design yields improved spectral purity of the radiated wave, and better radiation pattern. Experimental results have been presented in support of the theoretical conclusions.

Effect of Scintillation on Timing Applications of GPS in Indian Subcontinent

On the Indian subcontinent, scintillations are quite frequent and intense and have a longer duration during a peak period of an 11-year solar cycle. This phenomenon quite significantly informs us about the performance of the Global Positioning System (GPS). A special experiment has particularly been conducted to study the effect of scintillations on GPS time. This paper discusses the findings of this experiment. A degradation of timing accuracy of the order of 60 ns has been observed.

An Integrated GNSS–Microcontroller–GSM System for Various Application Developments

Global Navigation Satellite System (GNSS) is used to obtain user’s position, velocity and time (PVT) information. A scheme of using a low-cost, single-frequency multi-constellation GNSS hardware has been proposed here which can be used for several applications. The realization of the concept utilizes output data from a GNSS module in National Marine Electronics Association (NMEA) format that may be used by microcontroller and auxiliary hardware for location tracking, time synchronization or stamping and atmospheric monitoring purposes. The use of multi-GNSS is expected to provide enhanced capability of the generic system.

Lifetime Performances of Modernized GLONASS Satellites: A Review

Abstract GLONASS, successfully operating during 1990s became unusable by early 2000s. Following a revitalization and modernization plan since 2004, GLONASS constellation has been completed again by the end of 2011 and the use of GLONASS is gaining popularity. Because of the previous experience, some scepticism exists among the stakeholders in using GLONASS for reliable solution and application development. This paper critically reviews the operational lifespan of GLONASS satellites launched between 2004 and 2016, as this is an important contributor towards reliability and sustained operation of the system. For popularization and extracting full benefits of GLONASS as stand-alone system or as an active component of multi-GNSS, major issues of assuring the minimum sufficient GLONASS constellation (of 24…23 satellites), efficient design implementation and the modernized ground control segment development and operation need to be properly taken care of by the system operators.