Portland State University. Department of Engineering and Applied Science.
Date of Publication
Master of Science (M.S.) in Electrical and Computer Engineering
Digital electric filters -- Design and construction, Signal processing -- Digital techniques
1 online resource ( 2, ix, 89 p.)
The 24-bit Motorola DSP56001 processor will be used in combination with the DSP56ADC16 and the PCM-56 to design a good FIR compensation filter. Our objective is to digitize the input analog signal, and to compensate for the attenuation in the magnitude response of the digital sine wave. Two different experiments will be conducted, a hands on approach, and a simulation program. The first one will be realized directly, using the DSP system. We will determine the magnitude response of the system, and then deduce the coefficients of the FIR sin(x)/x filter. A look up table will store those values which will be fetched by the DSP program. With a minimum set of instructions we will generate a new digital output sequence after a N-point circular convolution is performed. The output signal is a good reconstruction of the input signal at frequencies below 22 Khz. However, a second experiment will be needed to improve this FIR sin(x)/x compensation filter, because we are not able to go beyond a 300-point impulse sequence. After that value (300-point), the time that each value is read and is ready to be processed by the DSP56001 becomes smaller than the time each instruction in the DSP program is executed and written to the PCM-56 via the SSI register. To be able to expand our experiment, we need to write a simulation program. A simulation program of the previous experiment, which take as input the measured magnitude response of the system. The challenge will be to find ways to map the frequency domain, by using the maximum value of each linear convolution sequence, with a finite input sequence. A step by step approach will be drawn until our final objective is reached. Our final step will be, to increase the number of sampling point in the frequency domain and will be to demonstrate that the result of the simulated program value will coincide with our objective, which is to compensate for the attenuation of the magnitude response of the system. By increasing the sampling frequency we will eventually obtain a good compensation filter.
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Fakhry, Nader, "Design of a Digital Compensation Filter" (1995). Dissertations and Theses. Paper 4961.