Digital frequency analysis techniques are used to determine the frequency content of a set of time-dependent data and to improve the quality of the data by eliminating undesired frequencies. This report provides an introduction to the use of these techniques with nonrandom data. Included are guidelines for acquisition and processing of data, calculation and interpretation of digital spectral estimates, and application of digital filters. The techniques are demonstrated by use of three examples derived from wind-tunnel data: (1) frequency analysis of 3-DOF angular motion data;(2) elimination of extraneous frequencies in dynamic stability data;and (3) determination of control surface forcing function frequencies.
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