Debapratim Ghosh

A four branch microstrip coupler with improved bandwidth and isolation

This paper discusses the design of a four section branch line microstrip coupler at 900 MHz. The coupler exhibits return loss better than 20 dB for the frequency range 625 to 1180 MHz. A peak isolation of 44 dB is achieved, with the overall isolation above 20 dB for the range 680 to 1195 MHz. This design also addresses the problem of large branch impedances associated with four branch couplers. The coupler has been fabricated on a glass-epoxy FR4 substrate, thus making it a very low cost solution. The designed branch line coupler finds uses in narrow-band network analyzers for incident and reflected power measurements, and in the CDMA (824 - 894 MHz) and GSM900 (890 - 960 MHz) band applications.

e-Prayog: A new paradigm for electronics laboratories

In engineering education, laboratories provide hands-on experience to students. However, scarcity of equipment, trained faculty, maintenance, upgradation and scheduling of experiments for these laboratories is a big challenge for developing countries like India. Rapid development and ever increasing use of Information and Communication Technology (ICT) has revolutionised the education system by eliminating limitations in terms of physical distance, time and access, by providing equal opportunity to everyone, irrespective of place and time. The purpose of this paper is to give an overview of the project, e-Prayog, at IIT Bombay as part of Virtual Lab project, an initiative by the Ministry of Human Resource and Development (MHRD) under National Mission on Education through ICT (NMEICT). As a part of e-Prayog, various electronics lab courses have been developed with four modes, viz., interactive tutorials, computer simulation, remote access of a real experiment, and low cost kit based experiments with complete Learning Management System (LMS).

A Broadband Active Quasi Circulator for UHF and L Band Applications

This letter presents a compact, broadband three-port MMIC-based quasi circulator for UHF and L bands. As a motivation and application, the use of this circuit in a network analyzer is presented. The circuit is designed using differential amplifier and lossy broadband combiner to obtain effective phase cancellation for high directivity. The designed quasi circulator has return losses at all ports better than 10 dB and reverse isolation above 30 dB in the frequency range from 0.2 to 2.5 GHz. The quasi circulator has directivity of 15 to 52 dB and load dynamic range of 10 to 49 dB, over the 0.2 to 1.7 GHz band. The proposed circuit thus can be used in portable network analyzers and other applications designed for the UHF and L bands.

A portable solution for microcontroller laboratories

This paper describes the development of two portable low-cost active learning platforms for a course on microcontrollers. These platforms are designed and developed at Indian Institute of Technology Bombay (IIT Bombay), India. The motivation behind the development of these platforms was to help engineering colleges across the country to upgrade their laboratories with modern microcontroller platforms along with comprehensive learning resources, free of cost, as part of Virtual Labs, a national level project. Both platforms were deployed at IIT Bombay and some other engineering colleges on pilot basis to investigate their effectiveness.

An introductory lab course in Digital Design: On-line and on-site laboratory solution

This Paper describes the development of a low-cost Complex Programmable Logic Device (CPLD) based development board and remote access to the same to complement an undergraduate course in Digital Design. The low cost boards has been made available to the engineering colleges in India on request for improving the laboratory resources at their end. The remote access to these boards can further scale up the facility to cater to larger number of users. The entire development has been as a part of the Virtual Lab project running at national level in India.