Austin, Texas
June 14, 2009
June 14, 2009
June 17, 2009
2153-5965
Computers in Education
9
14.1162.1 - 14.1162.9
10.18260/1-2--4938
https://peer.asee.org/4938
501
Thad B. Welch, Ph.D, P.E., is with the Department of Electrical and Computer Engineering at Boise State University, Boise, ID where he is a Professor and Chair of the Department. Dr. Welch's research interests include the implementation of communication systems using DSP-based techniques, DSP education, and RF signal propagation. He is a member of ASEE, IEEE, Tau Beta Pi, and Eta Kappa Nu. E-mail: t.b.welch@ieee.org
Cameron H. G. Wright, Ph.D, P.E., is with the Department of Electrical and Computer Engineering at the University of Wyoming, Laramie, WY. His research interests include signal and image processing, real-time embedded computer systems, biomedical instrumentation, and engineering education. He is a member of ASEE, IEEE, SPIE, NSPE, Tau Beta Pi, and Eta Kappa Nu. E-mail: c.h.g.wright@ieee.org
Michael G. Morrow, MEngEE, P.E., is a Faculty Associate in the Department of Electrical and Computer Engineering at the University of Wisconsin, Madison, WI. His research interests include real-time digital systems, embedded system design, software engineering, curriculum design, and educational assessment techniques. He is a member of ASEE and IEEE. E-mail: morrow@ieee.org
Travis J. Kent is a recent graduate from the Department of Electrical and Computer Engineering at Boise State University, Boise, ID. His academic interests include real-time DSP, image processing, pattern recognition, and digital communications. He is a member of Golden Key International Honor Society, Eta Kappa Nu, and IEEE.
Teaching with Software Defined Radios
Abstract
This paper discusses the utilization of a relatively inexpensive wideband radio receiver in combination with a digital down converter (DDC) based data recorder to capture and record real world radio signals. The resulting in-phase (I) and quadrature (Q) data files are then imported into M ATLAB for processing. This batch processing of real world radio signals allows for a tremendous amount of classroom flexibility in the discussion of software defined radio topics.
1 Introduction
There is a great deal of interest in the DSP algorithms necessary to demodulate communications signals. While a number of existing courses cover these topics, the use of real world communi- cations signals to develop and test these algorithms can be problematic. For many universities, the largest challenge in working with real world signals is the cost of the equipment necessary to detect, track, and capture the signals of interest. Two instrument grade, but costly, solutions to this signal capture problem can be found in references1 and.2
An alternative to the instrument grade test and measurement equipment solution is the use of a commercial-off-the-shelf system that was originally designed to support the amateur radio com- munity. A photograph of the high speed streaming digitizer, SDR-14,3 is shown in Figure 1. In this capacity the system provides filtering, amplification, and samples for signals from 0.1 MHz to 30 MHz. The resulting information is then streamed as decimated in-phase (I) and quadrature (Q) data to a host computer using a USB connection. Figure 2 shows a typical display for a system setup to capture a weak commercial AM radio station’s signal.
Unlike a number of available signal capture devices, this system is reasonably priced (approxi- mately 1,000 USD) and is only limited in its recording capability by the available storage of the host computer’s hard drive. For example, a one minute recording of an AM radio station created a 10 MB file.
2 Commercial AM
Using only a simple loop antenna connected directly to the SDR-14, the signal is captured and the resulting file is imported into M ATLAB for processing and algorithm development. For AM
Welch, T., & Wright, C., & Morrow, M., & Kent, T. (2009, June), Teaching With Software Defined Radios Paper presented at 2009 Annual Conference & Exposition, Austin, Texas. 10.18260/1-2--4938
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