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Unformatted text preview: UCLA Electrical Engineering Professor Jain EE 113D TA Delbert Huang Experiment 1 Frequency Synthesis Purpose To implement a frequency synthesizer using a simple, modi ed, table look-up method. To modify the program to enable the generation of piecewise linear approximations of triangular, square and other waveforms at di erent frequencies. Introduction DSPs can be programmed to generate arbitrary waveforms with great precision and exibility. In this experiment, we will program the TMS320C54x chip to generate sine waves using a simple modi cation of the traditional table look-up method. This is useful in communications (e.g., frequency hopped modems, PSK modems, spread spectrum), testing (e.g., precision signal generators) and control applications. There are many ways to generate sinusoids using DSPs. For the DSKplus, one technique is to use the AC01 A/D, D/A chip's embedded lters. If we force the output of the D/A to oscillate between two extreme values every sample period (or, in essence, try to follow a square pulse) then the output lter will pass only the fundamental harmonic and suppress all higher harmonics. The output will thus be a sinusoid (provided the lter parameters, sampling, etc. are set-up appropriately). In a similar fashion, a table can be created which can then be used to instruct the D/A to output values listed in the table at the sample times. Any arbitrary waveform can thus be approximated, with the constraint that sharp transitions will be smoothed by the AC01's output lters. The second part of this experiment will be some simple waveforms, and to experiment with sampling times, output frequencies which a ect the quality of the output....
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- Spring '09