Study of Modulation Using Graphical Programming and Virtual Instruments

INTRODUCTION Technologies change fast. As these changes occur, industries need trained technologists and scientists to meet their new workforce requirements. Advanced electronics and computerization are revolutionizing today's industries and the engineering technology and science programs are under pressure to modernize their programs to meet the challenges of this changing technology or to maintain the accreditation of the programs. This requires upgrading laboratories with modern equipment and calls for increased funding and resources. But in recent years there is an increase in enrollment and decrease in resource allocation making it increasingly difficult to modernize the laboratories to provide adequate levels of laboratory and course work (Korrapati & Swain, 2000). This calls for alternative cost effective methods such as Computer Based Virtual Engineering Laboratory (CBVEL), which can be accomplished by using the following: A Graphical Programming software (LabVIEW) and hardware (DAQ boards, GPIB interface etc.) from National Instrument. B Object Oriented Programming Software (Visual Basic, Java). We strongly believe that by modifying the existing laboratories through the addition of computers with appropriate DAQ and SCXI instrumentation, software (LabVIEW, Visual Basic, & Java) we can better educate and train our graduates to serve the needs of the technological and engineering community. Students will be skilled with hardware and software that is used throughout industry, at other undergraduate institutions, and graduate schools. Because of the flexibility of Visual Basic, LabVIEW and the associated interface, the system will be customized to suit the instructional and research needs of various departments. Virtual Instruments (VIs) relating to different courses will be integral part of this CBVEL. Examples of some of these VIs are Digital Electronics, Analog and Communications, Digital Signal processing, Digital Filters. These modules will be used to better train the engineering technology, sciences, and information technology graduates (Swain, Anderson, & Korrapati, 2000). This paper is arranged as follows: BLOCK DIAGRAM OF CBVEL The block diagram of CBVEL is presented below (Swain, Anderson & Korrapati, 1999): [ILLUSTRATION OMITTED] The various component of this CBVEL are personal computers, LabVIEW software, programming languages like C++, Java, Visual Basic, DAQ cards, GPIB and other interfaces. These components can be purchased from National Instruments. The LabVIEW graphical programming language is extremely versatile, and can be used to design and develop Virtual Instruments for various courses. The following are some of the application areas of LabVIEW: Simulation--simulates physical processes Data Acquisition--data acquisition from outside source Data Processing--built in analysis library that includes signal generation, measurement, filters, windows, curve fitting, probability and statistics, linear algebra, and numerical methods, Instrument and Control--Virtual Instruments (vi) Program Development--Object oriented/graphical programming Fuzzy Logic--fuzzy logic tool box ANALOG COMMUNICATION VIs This section describes in brief the underlying principles behind Amplitude Modulation, Frequency Modulation and Demodulation (Miller, 1996). AM ANALYSIS The frequency of human voice ranges from about 20 Hz to 3000 Hz. Transmission of such low frequencies as radio waves is impractical and useless because of a) interference problem and b) the largeness of antenna. The solution to this problem is Modulation. Modulation is a process of mixing a low frequency information and high frequency carrier through a nonlinear device. The transmission takes place at the high frequency (the carrier) which is modified to carry the low frequency information. …