June 20, 2010
June 20, 2010
June 23, 2010
Computers in Education
15.131.1 - 15.131.17
Advanced Functions of Java-DSP for Use in Electrical and Computer Engineering Senior Level Courses Abstract
J-DSP is a java-based object-oriented programming environment developed by Arizona State University as an educational tool for teaching fundamentals and applications of Digital Signal Processing (DSP). This paper presents three new J-DSP modules developed for presenting advanced DSP applications including: feature extraction in music and audio signals, wireless communications, and adaptive echo cancellation.
The feature extraction demonstration enables online simulation of different algorithms that are being used in speech and speaker recognition. Additionally, applications revolving around content-based audio classification and Music Information Retrieval (MIR) are demonstrated. Specific functions that have been developed include modules that are used widely such as pitch detection, tonality, harmonicity, spectral centroid and the Mel-Frequency Cepstral Coefficients (MFCC).
The acoustic echo cancellation tool would help the DSP students to get acquainted with the practical industry applications of the adaptive FIR filters. An acoustic echo canceller (AEC) is used to cancel the unwanted acoustic echoes in telecommunication applications where the loudspeaker and microphone are used in the same vicinity such as teleconferencing. The users of this tool can chose from different signals, e.g. white noise, speech, and music to be played by the loudspeaker to learn the effect of input signals on an acoustic echo canceller. The users can also adjust the length of simulated acoustic impulse response to simulate different acoustic environments, such as car, conference room etc. The number of adaptive filter taps in LMS adaptive filter can also be adjusted. Finally, the residual echo is obtained by subtracting the estimated echo signal from the original echo signal.
The wireless communication tool concentrates on the physical limitations of wireless power amplifiers and how to correct for them using a DSP technique known as predistortion. Wireless power amplifiers typically operate as class AB devices and are subject to a variable amount of clipping depending on input signal amplitude. This variable amount of clipping changes the gain at the fundamental frequency, which must be corrected. It also introduces harmonics that in isolation are easily filtered, but for multi-tone signals are generate harmful mixing products. The gain-based predistorter is described for both memory and memoryless amplifiers.
The simulation software is accompanied by a series of computer experiments and exercises that can be used to provide hands-on training to class participants. This effort is part of a combined research and curriculum program funded by NSF that aims towards exposing students to advanced engineering concepts. The modules developed can be used in signals and systems, communications, DSP, and mixed-signal courses.
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