Using periodic data to define an amplitude curve

Select Periodic to define the amplitude, a, as a Fourier series:

a=A0+∑n=1N[Ancosnω(t-t0)+Bnsinnω(t-t0)] for t≥t0,a=A0     for t<t0,

where t0, N, ω, A0, An, and Bn, n=1,2⁢…⁢N, are user-defined constants. For more information, see Defining Periodic Data.

  1. Display the Edit Amplitude dialog box as described in Selecting an amplitude type to define.
  2. Click the arrow to the right of the Time span field, and specify how you want to define the amplitude as a function of time:

    • Select Step time for time that is measured from the beginning of each step.

    • Select Total time for total time accumulated over all non-perturbation analysis steps.

  3. In the Circular frequency field, enter ω, the circular frequency, in radians per time.
  4. In the Starting time field, enter t0.
  5. In the Initial amplitude field, enter A0, the constant term in the Fourier series.
  6. In the data table, enter values for A, the coefficient of the cosine terms, and B, the coefficient of the sine terms. For detailed information on how to enter data, see Entering tabular data.
  7. Click OK to save your amplitude definition and to close the Edit Amplitude dialog box.