PSPICE Simulation Program with Integrated Circuit Emphasis CH

PSPICE计算机仿真 Simulation Program with Integrated Circuit Emphasis

CH 13 FOURIER SERIES 傅立叶级数

n Decay (衰减)

13. 1 Pulsed Sources

The pulse parameters are n n n n V 1 V 2 TD TR TF PW PER initial value (volts) pulsed value (volts) delay time (seconds) rise time (seconds) fall time (seconds) pulse width (seconds) period (seconds)

13. 2 Fourier Analysis n Example 22 illustrates a pulsed voltage source, the PSpice computation of the Fourier series coefficients, and the Probe computation of the Fourier transform coefficients.

Example 22 n n n Suppose that the pulsed waveform shown in Fig. 117 a is input to the RC circuit shown in Fig. 117 b. Use a Fourier series analysis of the input waveform to predict the frequency content of the output waveform for two values of C: 1 u. F and 10 u. F. Then use the Fourier transform mode in Probe to confirm the PSpice analysis and to display the frequency spectra graphically.

Solution n n We begin by computing the Fourier series components for the pulsed voltage signal shown in Fig. 117 a. Note that this waveform has two properties of symmetry: odd symmetry and half-wave symmetry. These symmetry properties tell us several things about the Fourier coefficients:

n n The dc component is 0. The Fourier series has only sine terms; the an coefficients are 0 for all values of n. Only the odd sine terms are nonzero; the bn coefficients are 0 for even n. Because of the form of the an‘s and the bn ‘s, the Fourier coefficients expressed in magnitude and phase-angle form are

Fig. 118 Sch

Fig. 119 Vpluse Property

Fig. 120 setting

Fig. 120 a

Fig. 121 output (Maybe wrong!)

Fig. 122 Probe

n n Trace/Fourier (Fig. 123 a) Plot/axis settings… (Fig. 123 b)

Fig. 123 a

Fig. 123 b

Fig. 123 fourier

Fig. 124 output

Fig. 125 10 u. F

Fig. 126 10 u. F-fourier