The stationary signal assumption is convenient as its signal processing methods are the minimum effort required to characterize periodic signals and therefore the most common. However, signals from rotating machines have been found to naturally be characterized as cyclostationary. The existent of natural phenomenon such as, shaft imbalances, turbulent fluid flows, friction, combustion forces, and torsional vibrations create modulation effects, that can be seen in the measured signals. These observed modulations in pump noise and vibration signals are synonymous to amplitude modulations (AM), frequency modulations (FM), and potentially phase modulations in electrical systems. Having this knowledge, the fluid power noise, vibration, and harshness (NVH) researchers can draw from an enormous amount of progress made in the modern telecommunication signal processing methods of cyclostationary signals. This article introduces the basic concepts of cyclostationary signals, some of their signal processing techniques, and a simple example of analysis for a positive displacement machine through the cyclostationary paradigm.

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