A laboratory project in which the students build a simple DC1 MHz spectrum analyzer using only an oscilloscope, function generator, and a custom built-mixer/IF section is described. After assembling the spectrum analyzer, the students use it to explore the spectra of a number of different waveforms including amplitude- and frequency-modulated sine waves. The laboratory helps the students develop a feel for the meaning and significance of the mathematics they have learned relating the time- and frequency-domain representations of signals (i.e., the Fourier series, and Fourier and Laplace transforms). In addition, the laboratory introduces the students to mixing (i.e., heterodyning) and improves their understanding of their test equipment and its possible uses. The laboratory is suitable for use in a typical junior-level signals and systems course, a junior-level circuits course, a communication course, or a measurement course.
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