Bill Hargin

Understanding key differences between time and frequency domains.

As March approaches each year, I can count on the bullfrogs around our neighbor’s pond to be out in force, memories of days coaching baseball and softball, my wife’s birthday, and on March 14, “Pi Day,” which has been celebrated by geeks around the globe since 1988. I take the day seriously due to pi’s prevalence in almost every field of science, ranging from astronomy, electromagnetics, physics, to probably several other fields I’m not even thinking about. How did pi find its way into so much science, and what are the implications for electromagnetics?

Before we go into details regarding the time and frequency domains, it’s beneficial to discuss the “unit circle” and radians. A unit circle is simply a circle with a radius of 1 (regardless of units). The circumference of a unit circle is 2π, meaning that one cycle would be 2π, and there would be 2 x 3.14 radians required to complete the circle. This is illustrated in FIGURE 1.

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